Max M. Carter Dot Com
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July 22, 2024

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[Mon Oct 24 23:22:32 2005] amblog...

Well Max... I just finished reading the story of "Cat Radio". It captivated me even though I knew of the outcome beforehand.Be an even more wonderful world I'm thinking, if every little girl were able to have the kind of bonding memories that Tegan has of having this sort of lightly illegal alliance (being in cahoots) with her Dad, sharing an interest – while, all the while, having fun!Enjoyed the read.Carlos


[Sat Oct 29 11:44:26 2005] about....

Hi Max,I enjoyed reading about the AM transmitter project - the push-pull topology is what I used for mine except I used IRF620's and was about 10dB down on your for output power! I used fet driver chips with a transformer to force a square wave on the gates. I am curious about your use of the 2N2222 as the complimentary drive - was it really happily driving those big fat (1200pf or so input) fets at nearly 2megs!!??I am wondering if I ought to give it a go as I have a 9100b Optimod AM broadcast audio would be fun to join in the 160M phone nets using something like that!Kind Regards,Rash.


[Sat Oct 29 22:56:23 2005] fmtx.....



[Mon Oct 31 09:18:16 2005] home.....

2+2=4the end.


[Mon Oct 31 18:06:53 2005] home.....

Hi Max,

This is just a test.%%*




[Tue Dec 6 20:53:01 2005] fmtx.....

I've worked quite a few years as an engineer in TV & FM broadcasting; as an announcer; as a public safety/lmr 2-way radio tech; as a telephone company datacomm tech; as a commercial satellite tech; as a catv headend/distribution tech; have built quite a few 200' Rohn-25 towers; am a "ham," design/install surround sound home theaters; catv systems, etc. Have long thought about building an FM stereo lpfm station; possibly a pirate; also want to build a digital tv cable system, among other things. THOROUGHLY enjoyed your website. Funny, my wife is nicknamed "Cattie," and my daughter, "Little Cat." You are obviously a wonderful family. Is a pre-etched & drilled pcb, and parts, available for the '96? With YOUR mods? I would LOVE to build one; would put it on the air right away. I would even allow regularly scheduled programming thru my broadband connection FROM YOU to continue some of your "catcasts!" I wish you and your sweet little daughter the best. You are most fortunate to have each other. God bless. Dean ;


[Tue Dec 6 21:03:59 2005] twist....

This is from Dean...I have some lowband Motorola Micor & Mitrek 100-watt mobiles, some GE 100-watt mobiles, some Uniden 800 meg SMR trunking mobiles, and some low band GE stations; all of them complete and tested good condition. For sale/trade. Anything special you are looking for that I might could help locate for you out here in the oil fields of West Texas? soon to be General or Extra AND Commercial!


[Sun Jan 15 20:50:53 2006] home.....

can you send me an FSK transmitter and Receiver. it would be a great help.. thanks


[Sun Jan 22 23:22:41 2006] about....

Nice work! I was just wondering if you ventured out again into the broadcast spectrum with your AM rig. I've & ("we") have enjoyed "Holiday Pirating" since the 70's. But the money hungry commision has cluttered up the spectrum so much that "NOW" you can't find a clean spot to operate and be heard without using some muscle & creating a little splatter. Looks like we'll have to get retro and utilize some AM emmisions to continue the tradition. Just when that FM system was sounding so good too! I'm trying to stay away from Ch.6 audio 87.75. But 87.9 might be my only other option. Oh well! We've had fun so far! Just don't want to be limited to a net audio stream! Not very exciting! Good for friends out of the listening range, and maybe linking to a remote xmtr, but... Have fun! Comment?


[Fri Feb 17 11:03:21 2006] amblog...

Hi Max! Long time, no chat. Found your website fascinating. Would love to talk. I live in the far northern corner of Washington State. I work (still) at a test lab .73, Jim .


[Mon Apr 3 13:06:33 2006] fmtx.....

Nice set of well thought-out mods! I'm not sure why you used the composite as the point for checking your modulation level. I would have looked at the AUDIO rather than the whole thing. I understand the idea of taking the BB (TP4) signal (after all, it has the sum signal). However, the pilot will surely mess with your overall levels. Perhaps you can compensate with the threshold setting of the limiter.It might also be worth adding a diode clipper after the limiter - it's really brutal, and can sound horrible, but if correctly set will completely prevent overshoot modulationpeaks.


[Fri Apr 7 00:13:15 2006] classe...

nice comment box


[Fri Apr 7 07:17:48 2006] home.....



[Fri May 12 21:34:44 2006] home.....

Hi Max,Good lookin' laser pics. I'm still trying to get the mini-movie to run. I don't know if it's the video or my computer that's the problem, but it's likely the computer.The white light video effect from the laser has to be clipping of the data read by the sensor. As in, "white is just really bright black."John


[Sun May 28 20:18:45 2006] catradio.

Catradio was a great story (and a nice way for you and your daughter to share some time together,) good it wasn't in the crow-bar motel! Funny story, I had acartoon, to that effect hanging on mybedroon wall when the FCC paid me a visit, many many years ago, 1966'ish Ithink. 6c4 osillator driving 6l6, plate modulated with back to back CTC universal audio output transformer, Dynco hi-fi amp. Operated a "request" radio station, maybe 4 days. I lived inMilwaukee Wisconsin area, FCC heard me by a FCC monitoring station (across lake Michigan) in Michigan. I still have myofficial letter & a reel to reel tape of"crazy dave's" radio station. Regards &73's


[Sun Jun 4 12:30:07 2006] catradio.

LOVE IT! JUST BE MORE CAREFUL NEXTTIME. It CAN be done for years withsufficient care. Best of luck es 73.


[Sun Jun 11 05:25:47 2006] home.....

Hello from Atlanta!!!


[Wed Jun 14 14:34:40 2006] gatrip...

These were great, thank you so much for sending them. You gave me a good idea of the ceremony etc. Love the aquarium shots. I too wonder if Mom helped build that boomer. I'll try to do this for you when we go to New Zealand....I've nothing from Fauna's graduation but will try to get her to send me some. Lucky you got to be sheltered while daughter was exposed. Just the opposite for us with daughter nicely sheltered from the rain and us staring at umbrellas. Aren't mortar boards funny hats. Love, Tracy


[Wed Jun 14 14:41:05 2006] gatrip...



[Thu Jun 15 13:10:58 2006] gatrip...

Hey,Everyone looks relaxed and content! You look like you had a great time.See you tomorrow!The gang at SFSThank you for sharing..............


[Thu Jun 15 16:50:11 2006] gatrip...

Great pictures. Keep the site its excellent.Anna


[Tue Jun 27 07:10:05 2006] classe...



[Wed Jun 28 03:46:08 2006] classe...



[Tue Jul 4 04:16:55 2006] classe...

please I'm a nigeria undergraduate in one of nigeria universities,i'm PHILIP, i want to learn how to design a transmitter.can i learn from your company.


[Sun Jul 30 10:04:08 2006] home.....

Hi!how is the rms power of 1710khz trans. and how is the pep?thanks!


[Sun Jul 30 10:06:45 2006] home.....

Hi!how is the rms power of 1710khz trans. and how is the pep?thanks!Can i tune this transmitter 550-1800khz?


[Fri Aug 25 14:54:37 2006] catradio.

Hi, That was a good story and enjoyed reading it. Glad to hear Cat Radio lives on. I operate an internet radio station at as well as a LPFM from my location. The FM signal stays within the part 15 limits most of the time :o) I am legally licensed to play copyrighted music on both. My transmitter is a pci card adjustable type with a max of 1 watt but reaches several miles with my 1/4 wave antenna when at full power. The town I live in also has no FM station. The ones that do come in play stuff I (and most others my age) don't want to hear. I hope the laws will change for LPFM so that us smaller broadcasters can get licensed and reach our local communities with an alternative to the new age music. Take Care, Wildun ..


[Fri Sep 29 22:10:41 2006] home.....

im looking for some tune up ? hop ups for my galaxy DX949 raido plese help me thanks thanks again


[Wed Oct 18 08:59:29 2006] amblog...

How can I find a 60 watts AM transmitter for a community station?


[Fri Oct 20 23:40:31 2006] amblog...

Hello! Interesting stories you have regarding your AM and FM low powered days. Do you ever fire up eith the 35 watt AM or the 14 watt FM transmitters anymore? I know a guy that is considering putting on a low powered AM station in Rome NY, about 20 miles from me. Should be interesting to say the least.Bob-


[Sun Oct 22 04:28:16 2006] catradio.

Radio QRP - The Art of Low Power and Clandestine Operations need your support! QRP is The Art of Low Power Radio where the challenge is to operate and/or build AM radio transmitters using a bare minimum of components, money and construction skill. Why work QRO with a factory set, when homebrew QRP works really well! We are searching for the ultimate design of a Grenade transmitter or Grenade Clone with a minimum of 5-10 watt output and is complete and working! Can anyone help us locate such a unit? We would appreciate any ideas on how to design this rig. Information in this subject would be appreciated! Thanks!


[Thu Oct 26 20:36:31 2006] catradio.

you are the man, my mpx 96 started hissing and I lost all the schematics and stuff for it, its been so long since I built it I forgot what the adjustments were but found your page and was saved. I use mine to transmit out to the end of the driveway while plowing snow and working around the yard


[Sat Oct 28 17:09:28 2006] fmtx.....

i have a radio station. my exciter is not producing sound out for broadcast. but the lights indicates that i am get the input. please help me. my station is off now. this is my e-mail.


[Sat Nov 11 20:31:00 2006] home.....

Hi Max,I'd like to know what HTML command set to use to work on my pages. Can you refer me to the appropriate version?Tnx,John


[Sat Dec 9 15:33:27 2006] amblog...

I am totally a hobbiest, not that dedicated to anything. I have been trolling the internet since the late 90's looking for a variety of low-tech transmitter designs. The designs fall into two categories: one transister 'bugs' that can be built for $5-$10 and big fancy pirate rigs that require lots of hard to find (expensive) parts. I heard that P.O.W.s made recievers with rusty rasorblades, graphite pencil lead, coils of wire on toliet tissue rolls and a tank commander's headphone. I wanted to design the transmitter equivalent of that. It's gotten a bit fancier than that. It's all made out of NTE replacement parts and "magnet wire" and little bits of cat4 untwisted braid. I'm too chicken to take it on the air, but I think it may have as much as four watts of something. Running it into three 150ohm 5watt resistors in paralell they get warm like a coffee mug warmer, and once I stuck it onto a 130 foot random wire thrown over the house, grounded it to a cold water pipe and stuck one of those 12 volt garden lightbulbs in series with the antenna and it lit right up. It was winking brighter in time with the music, then about ten seconds was all I could stand. I was (and still am) afraid that an rf version of "shot spotter" will triangulate to within 60 feet of my house. So, I have yet to see how well it modulates off of the dummy load. I guess by all rights it is a three stage transmitter in one box.


[Wed Dec 13 13:23:58 2006] amblog...

Hi,How was the audio freq. response of your Globe with the "heavy Iron". Sound good on your 10 mile drive? I am currently working on that same setup with a Johnson Viking II. I take it that "Super Modulation" was not worth it. Im also on a quest for more info about that . The ARRL book doesnt have much information.Best Regards,


[Sat Dec 16 00:04:03 2006] amblog...

The trouble with obtaining or building a quality am transmitter is that there are several "kits" out there (of which some are better than others) which seem pretty promising on paper but are a let-down once assembled. They either have poor audio quality or are so complex in design that it is near impossible to troubleshoot them when they "go astray." As for that globe transmitter conversion, that was a work of genius. Some of the terminology was hard for me to follow even though I have an AAS Electronics Tech degree from DeVry. I have been heavily involved in amateur radio since I was in high school. One guy named Phil had an interesting kit/plan posted online called the Li'l7 transmitter which is a basic one-tube design. It is easy enough to understand the fundimentals of such a simple circuit as this, given it uses a basic tank circuit and heartly oscillator. It did not look too different from a one or two transistor AM transmitter, but probably is a little more powerful being a tube rig and all. The only problem with the circuit is that it puts out entirely too little power (probalby about 100mw) to do much of anything with. I am in need of a little (not much) more complex circuit diagram, say a two or three tuber that will put out say a watt or two. At least this would be easier to assemble than any darn computer or PLL controlled AM transmitter would be, and it would definately outpreform say an SSTRAM or A Ramsey AM-25 in high power configuration. Any suggestions of schematics for a simple AM transmitter in the one to two watt range would be greatly appreciated. Do you have any idea of how to "beef up" or add a second stage to a Lil'7 for a bit more power? I would sure appreciate it. That kit that Antique Electronic Supply makes is little better than the Ramsey AM-1 as far as stability and audio is concerned. I hope I haven't talked your ear off, but I was totally fascinated to read about this project of yours!'73


[Thu Jan 18 22:10:58 2007] fmtx.....



[Fri Jan 26 01:14:43 2007] fmtx.....

I always have terrible trouble with comment-related plugins that require me to put some line in the comment loop; I can never seem to find the right spot. Can anyone tell me where I should put the php line in my comments loop? I haven not modified anything much, and I would be very grateful. Thanks!


[Sat Jan 27 01:22:55 2007] fmtx.....

Bonjour! What a super websight! Very refreshing to peruse from where we live in Paris (France). I eat frogs and drink wine. Woold like more informatons on this. Best regards! Mikael.


[Tue Jan 30 19:16:39 2007] fmtx.....

Superb! (I wrote something else and then I read below that I aint supposed ter. So I deleted it.)


[Sun Feb 11 08:25:31 2007] home.....

Max, Wheres pretty Baby? SIGHH I see Laya but not Pretty Baby.


[Sat Feb 24 11:50:00 2007] catradio.

Read the saga of CAT RADIO today. Very impressed, it embodies the spirit that keeps Free Radio ALIVE. I operate a SW 10 watt am station here in the UK, 6278khz BYCROSS RADIO (INTERNATIONAL). Striving to bring you something a little different in a spectrum of computor controlled channel blasters!


[Wed Feb 28 06:02:03 2007] home.....

Good morning, Max. This thing is located on the north side of the air base in Anchorage: Wullenwebber.John*******


[Wed Feb 28 08:48:27 2007] home.....

Here ya go, Max:*******


[Sat Mar 24 20:56:58 2007] catradio.

Fascinating story! At least in your instance there was a real owner. Not some jumbo corporation. Radio has gone to the dogs! Long live Cat Radio.:)


[Wed Mar 28 17:35:52 2007] home.....

03/28/07Wow!I enjoyed the info about LASERS.Thank you,Ed


[Wed Apr 18 02:08:00 2007] catradio.

Does the anybody really own the airwaves? Prove it


[Mon Apr 30 07:25:57 2007] lasermod.

Hi Max,A suggestion:It looks like you added an LC filter to notch out your local AM station. Since most hobbyists live in urban areas with multiple strong AM stations, you might want to go with a low pass filter to take out the entire AM band. That would make the circuit more immune to other RF gear as well.John*******


[Tue May 1 18:09:33 2007] lasermod.

Hi Max,That sounds like a pretty simple alignment procedure to me.As an afterthought, almost everyone now has a PC and could use freebee audio software to act as a low freq scope. Add a divide by 10 chip for example and you could use to to set something like the FREQ adjust quite accurately. Or use a reference to a specific square wave level to set precise audio input levels. Lots of possibilities.John*******


[Fri May 4 08:11:48 2007] home.....

Hi Max,You might want to mention to folks not to point the laser beam concentrator at the sun. Cook the detector real quick.John*******


[Sun May 27 16:46:08 2007] lasermod.

Qool stuff!-Quahog


[Sat Jun 9 09:33:14 2007] home.....

Hi Max,The Photo-Snooping circuit looks good, and removing it from the FM circuitry does clean things up a lot. Good idea.John*******


[Sun Jun 17 03:40:05 2007] lasermod.

Great photos! I'm rustling up a similar laser pointer serial data comms. setup, to be driven by a Picaxe micro (see Picaxe insights => ). In fact a simpler approach to yours is at => you considered using a cheap telescope at the receive end?Regards- Stan


[Sun Jun 24 10:14:35 2007] classe...

hi MAX i m alex from greece . I am an amateur in AM BAND. 1600KHZ. I have an am pll exciter about 30watt output.I Want to help me on a linear amplifier about 250-300watt. do you have any circuit about this??


[Sun Jul 1 19:35:23 2007] classe...

This is an extremely well produceddocument, well done and thanks.I have not used a push pull pa beforebut intend to have a go, using regards Finbar


[Wed Jul 18 08:09:45 2007] catradio.

congratulations, what a pity some people have little better to do than cause grief to others.I was a broadcast engineer some time back and on a Sunday morning we radiated test card(Television station) and a tape of the most boring music you ever heard. One sunday I took a load of records in and patched out the test tape direct to the transmitter (I thought!) after two hours of playing our own music to those on duty getting ready to open the station we got a call from the transmitter site saying how nice it was to have some decent music for a change!!!We got stuck with "performing rights" costs of about ten thousand dollars but pleaded that we were not radiating for entertainment but for station alignment so they dropped it! Thank God! We had been "pirating" with a power of 150 kilowatts!!! now thats some pirate station.Regards to your daughter and tell her to keep up the good work, books are wonderful things and sadly becoming obsolete.Kindest regards Clive


[Thu Jul 26 14:58:27 2007] catradio.

i am a ham. i am also a pirate. i live in a small town in texas. i only go on the air a few times a year. i can transmitt up to 350 watts. it makes no sence why i enjoy the pirate life. i have made most of my equiptment.sounds like you have a great time. i guess we should be living in the 20's. too many rules and regs today.keep up the good way of life.


[Mon Aug 13 04:06:12 2007] catradio.

From Bryan Sir Max:i am bryan , I am doing my thesis right now on pirate radio however, i got a hard time assembling the my this trasmitter ("islander" from got the hard time looking for parts in the Philippines, and not an electronic person.sir since you ceased from operation would you mind sir if you would donate your equipments to us here in the Philippines i am sure it would be of help in the opration of vegetable farming here since there are no station in the area. Sir ould you please help me the and my fellowmen. thank you.Bryan


[Mon Aug 27 22:46:48 2007] classe...

Hi Max. My name is Agus. I m enjoying as a ham since 1979 when i was in middle school. I am intersesting in class e project and i found in the net your very clear project page. I m reproducing your schematic for 80 mtr band and it works at least i can produce RF. My problem is the power output is only 120 Watt.By knowing my problem i came back to see wheter i m overlooking something.Could you share your experience about my problem? Thanks for your help. Thanks Max 73s fer u es family.


[Sun Sep 9 18:42:07 2007] amblog...

I am trying to find transmitting mica caps for modify Johnson KW Matchbox tuner for 160. Do you have a source for 2 each 350 pf. transmitting mica caps?


[Mon Sep 17 02:51:24 2007] amblog...

Hi Mr. Carter,Thank you for putting up a nicely done technical web page and for sharing your equipment-building experiences with the Net.Sincerely,Pat


[Sat Sep 22 22:02:20 2007] lasermod.

I am looking for a receiver schematic to receive input from a laser beam for school. Do you have the schematic for the receiver you built for your project? If so can I get it? Thank youDavid


[Thu Nov 15 01:21:56 2007] fmtx.....

i am want PCB set modifications MPX96Thank you everymuch


[Fri Nov 16 10:31:45 2007] catradio.

Brilliant. truely Brilliant. My name is Rob, and I was raided this year in the UK for operating a 10 watt Shortwave pirate station from my boarding house. We were on air tuesdays ,Thursdays and weekends for a year and a half untill 'The Knock'. At 15, i am Offcoms youngest SW pirate. Good job they didn't hear of the AM MW set that is still running at weekends...Cracking read, and all the best.


[Thu Dec 27 15:55:59 2007] lasermod.

Hi Max.I enjoyed reading about Cat Radio and your various transmitter projects. It is nice to know that there are still some persons around who want to tinker with electronics and share their experience with others - even though you may buy almost every conceivable gadget on the earth on eBay for next to nothing.A. S.


[Mon Jan 22 13:43:05 2007] class....

Question for you: When opening a program window (such as IE) the window often comes up in its non-maximized mode. Clicking the 'maximize' button or double-clicking the bar at the top of the window always maximizes the window, but after closing the window and reopening at a later time, it comes back up in the non-maximized mode again(!), making the maximize step necessary again! How do you get the window to remember to come back up maximized??

(This seems to be a "feature" of WinMe for sure - not sure about XP.)


[Mon Jan 22 13:44:44 2007] class....

Start with all windows closed. Open up one window (IE for example) and maximize it. Leave it open. Now, open up another window (It will open up NOT maximized). Maximize this one too. Now close both. Open up a new window and it'll open up maximized.

Another way to do it, although not really correct, is if you open up a window and it's not maximized, you can resize it (by putting your mouse on the corner of the windows and dragging) to it's maximized position. When you close it and open another window, it should come up to the size you resized it too.

Hope this helps!


[Mon Jan 7 16:30:44 2008] fmtx.....

Please send us the PCB design, and the complete part list of of the circuit


[Mon Jan 7 20:36:44 2008] home.....

Good star story, Max.



[Tue Jan 8 06:30:59 2008] viewcoms.

I will forward your request to my PCB design guy..



[Tue Jan 8 08:33:23 2008] max......

Thanks John!

(LED illuminated star here.)



[Wed Jan 16 17:48:02 2008] classe...

Nice page. I just got done building a 50 watt AM transmitter a little while ago using a mosfet. I don't think the design counts as true class E but it puts out a clean good signal.
I find mosfets are the best way to build larger lower frequency transmitters today from longwave up to 3 or 4MHz.
If your interested here's my design..
(note it was kind of a makeshift rig and was my first ;)...

Anywho check out our message board at..


[Tue Feb 5 23:49:12 2008] amblog...

my compliments for your story, it's like my story , i have many years ago a small radio in my village , but i must shut down for bad laws in italy .


[Fri Feb 8 08:24:25 2008] viewcoms.

It sounds like Massimo and I have something in common.



[Tue Mar 11 12:15:40 2008] home.....

Nice site. A good couple of hours entertainment. (Make yourself the PDM modulator! You'll love it!)




[Mon Mar 17 04:49:15 2008] viewcoms.

Thank you Andy,

Actually, I tried for several months to get the PDM to work.. without success. So I went back to using iron..



[Mon Mar 24 21:29:26 2008] classe...

Lo felicito por su excelente descripci¨®n del amplificador Clase E de 200 vatios.
E realizado una sabana electr¨®nica en Excel, que me gustar¨ªa enviarle, donde desarrollo las sencillas formulas de Mark Mallory.

Entrando los valores del ejemplo de Mallory, da los valores esperados.
Entrando los valores de su amplificador, algunos no me coinciden y me gustar¨ªa conocer su opini¨®n al respecto.

La resistencia de carga en mis c¨¢lculos es de 22.2 ¦¸ y usted habla de 10 ¦¸ en su circuito
El condensador del tanque me da 2.433 pF y usted coloca 5.500 pF ( 0.0055 uF)

Me gustar¨ªa saber su correo para enviarle dicha sabana de Excel


Herbert Botero B.


[Tue Mar 25 09:34:04 2008] viewcoms.

Thanks for the nice comment, Herbert.

I went back and recalculated the inductor and capacitor values for the 1.71 MHz class-e AM transmitter and discovered an error in the design instructions given in the web article. The confusion comes from the fact that the 1.71 MHz circuit is a push-pull design, whereas the Mallory circuit is single-ended. The error (my error) is in the P (power) term in the first equation (calculating for L). Since the power is shared by two tank circuits, the P term in the first equation should be 1/2 the output power. I did not make that clear.

I have re-written steps 1, 2 and 5 to clarify the design procedure. Please retry it - use 200 watts for P.

Here are the results of my calculations:

Calculated L = 1.07 uH
AL value (for T400-2 core, from table) = 185
Calculated turns (on T400-2 core) = 7.6 (rounded to 8)
Calculated C = 4829 pF (I used 5500; I happened to have ten 1100 pF mica caps on hand)
Calculated Z = 11 Ω (approx. 10)

I don't have contact information for Mark Mallory. If you like, you can send the spreadsheet file to me as an email attachment, or upload the file here.

Sorry for the confusion.




[Thu Mar 27 05:17:54 2008] viewcoms.

As a result of the above exchange, I put a CALCULATOR on the class-e equations page. Click: /classexmtr/classecalc.html



[Sat Mar 29 00:10:12 2008] catrad...

Dear Max...I enjoyed reading of the escapades of Cat Radio! Your site is very interesting and your construction work looks superb.

I heard my first pirate back in 1969 (part of the Falling Star Network out of NYC)...although it has been quite a long time since I listened regularly, I have heard several hundred pirates in my day.

Last summer I was able to hear Radio Free Berkley from the car on a trip to northern California...what a nice find.

If you get a chance and have a tape of any of the broadcasts, I encourage you to post them here as .wav files.

Again, thanks for the interesting read...Bill Martin


[Tue Apr 1 05:21:10 2008] viewcoms.

Thanks for the nice comment, Bill! I'll consider your suggestion.



[Wed Apr 9 22:23:04 2008] classe...

Hi! Enjoyed reading your 200W Class E article. How did you avoid saturating the core of the PA system transformer (or 115VAC-115VAC isolation transformer given that aboput 5A DC is passing through it? Thanks, Floyd K2DUV


[Fri Apr 11 06:06:07 2008] viewcoms.

Thanks for the comment, Floyd. I had no problem with core saturation. There's a nice big ol' transformer in that PA amp. Lots of iron mitigates against the possibility of core saturation. I added a blurb in the article about it.



[Thu May 1 08:29:22 2008] classe...



[Fri May 2 07:53:29 2008] viewcoms.

You might want to get some protective eyewear, John. My understanding is that laser goggles are selected according to the wavelength of the laser you are using, i.e., so as to absorb in the wavelength range of that particular laser.



[Fri May 2 08:46:05 2008] viewcoms.

Class-e definitely ain't linear!



[Fri May 16 05:48:42 2008] amblog...



[Thu Jun 5 14:08:53 2008] classe...

you are not giving audio in put stage clearly please give this through
email thanku for yours corcut idea


[Thu Jun 5 14:12:46 2008] classe...

give a simpul shmatric of am tramsmitter with long range i think you used mpspet hi watt with parell more than above and increase the range
of trannsmitter and watt also


[Fri Jun 6 07:22:23 2008] classe...,

The [class-e AM transmitter] article shows the transmitter circuitry and gives some suggestions for interfacing a modulation amplifier. (The audio modulation power is supplied by the modulation amplifier.) As suggested by the article, many commonly available amplifiers, tube or solid-state, can be used - public address, home audio, car stereo, etc. The details of the modulation amplifier are beyond the scope of the article.



[Fri Jun 6 08:36:06 2008] viewcoms.

I've never had very good luck paralleling MOSFETS. Must be doin' somethin' wrong..



[Tue Jun 10 21:16:32 2008] home.....

I'm curious if you're the same Max Carter I served in the Air Force in Germany with. Ayers Kasern near Butzbach, Germany in the late 60's. I recall we were both into stereo's, built the "Brute 70" power amp. from scratch. Parts from Allied Radio & others. It does look like you in the pix. Let me know. You may respond to Luckey


[Thu Jun 12 05:48:44 2008] viewcoms.

Yeah, I'm the same guy, now 40 years older, retired and living in Wyoming (29 years). I still have that Brute 70, modified and repaired over the years but still going strong. I remained interested in electronics after leaving the service and have more or less made a living at it, plus doing a lot of hobby stuff.



[Mon Jun 16 01:41:32 2008] home.....

Nice site. Enjoyed reading about your radio broadcasting. Thanks for sharing that and other projects.
Kind regards from 'Down-under'


[Mon Jun 16 16:29:13 2008] viewcoms.

Thanks 'Down-under'!



[Tue Jun 17 14:30:08 2008] viewcoms.

give simpul hi watt long range transmitter you are not giving
smematric about 200w transmitte
give simpul ababul productto make


[Tue Jun 17 14:47:19 2008] viewcoms.

sorry sir,
parallel mospet means in rf out put stae we used pus pul type two mospet and increase this range through increase the pear of mospet like two pear & 3pear and increase volteg
like (ups or invertor) circut .and increase the range thanku for reading
and ancer me (112)


[Wed Jun 18 09:47:42 2008] viewcoms.

Here's a block diagram of the class-e AM transmitter (about the same as any other AM transmitter). Note that items marked "external" are not described (except in a general way) in the article:

Hope this is helpful.



[Wed Jun 18 10:14:00 2008] viewcoms.


Yeah, I know that in theory one can parallel MOSFETs to increase the power handling ability of the stage. I just have never had any luck doing it at the frequencies and modes (class-e) that I've tried..



[Fri Jun 20 12:56:58 2008] home.....

what is class e type transmitter and other a,b,c type transmitter


[Fri Jun 20 14:09:04 2008] viewcoms.


Class A - output MOSFET (or other device, i.e., bipolar transistor or tube) conducts during 100% of the RF cycle time,

Class B - output device conducts 50% of the RF cycle time,

Class C - output device conducts less than 50% of the RF cycle time (typically about 45%),

Class E - output MOSFET acts as a switch, conducts only when the drain voltage is at 0. This is usually around 50% of the RF cycle time, but can vary depending on circuit parameters.

Look on the internet for further explanation of the various "classes". Wikipedia is usually pretty good.



[Mon Jun 23 12:43:37 2008] viewcoms.

sir ,
still ihave adout 3.42 mhz carrier source means ?where i get this get idea details thanku for ancer me


[Tue Jun 24 06:08:30 2008] viewcoms.


Quoting the article: "...a signal generator, crystal oscillator, VFO or other source.." This would probably work:



[Wed Jun 25 00:17:40 2008] viewcoms.



[Thu Jun 26 12:06:58 2008] viewcoms.

i have a 500w/1kw transmitter circut can you give idea to make simpul this ai 1.9mb give your email add i give you this thanku


[Thu Jun 26 13:17:29 2008] viewcoms.


I emailed you regarding this. Check your email.

Or upload the file here.

Your choice.



[Thu Jun 26 23:52:22 2008] classe...



[Fri Jun 27 06:46:19 2008] viewcoms.

You might try phrasing your comment as a complete sentence..



[Fri Jun 27 11:55:49 2008] viewcoms.

i sent this circut diagram through uplod option but it not give finish command after sending it will be heng up so if you are not receive than sent me e mail clearly my e mail and write (max) also then i understand uoy know there is more adv mels are comming and confus the peapul thanku sir


[Sat Jun 28 15:02:59 2008] max......

For what it's worth, here is a block diagram of the AM stereo transmitter Illiraj55 is referring to. About the only difference between a "regular" (mono) AM transmitter and a stereo one is the addition of the stereo processor/exciter. This one happens to be a C-QUAM exciter.

Note that the outputs of the processor/exciter consist of 1) a phase-modulated carrier at the transmitter's RF operating frequency and 2) a pulse width-modulated (PWM) AUDIO carrier, usually at around 100 kHz. The PWM stream is filtered in the modulator to remove the 100 kHz carrier and the two signals (RF carrier and now analog audio signal) are combined (multiplied) in the RF power amplifier to produce the composite stereo output signal. The composite signal is processed at the receiver to extract the original stereo audio signals.

I don't think AM stereo is used much anymore, at least in the US.

Hope this is helpful..



[Sun Jun 29 11:54:12 2008] viewcoms.

in our country radio transmitter is ilegal i heard that is in india . sir any idea to make transmitter in legal purpose houw can i get licance or any friquncy that is free for transmitting or hobby purpose any ligal sdvice if you know then give idea to solve my problame thanku sir


[Sun Jun 29 15:46:46 2008] max......


I don't know how to get a broadcasting license in India but, like many places, if you have the equipment, there is not much that prevents you from broadcasting WITHOUT a license.

(I didn't actually say that..)

My suggestion is to use FM. FM transmitters are generally simpler and cheaper, antennas much smaller, and coverage (transmitting range) is usually equal to or greater than AM for wattages less than 100 or so.

I don't know if low-powered FM transmitters are available in India, but they are available worldwide.

Type into Google terms like 'low-power FM', 'LPFM', 'pirate radio', 'FM transmitter', etc.

Hang around pirate radio forums like or

Drop a question on there about where to get transmitting equipment.

Some sources that I know about are: kits mostly; require soldering kits; require soldering, adjustment skills, test equip ready-built mostly

There are many others.

Importation is a problem in some countries. I don't know about India.

It appears that the FM band in India extends from about 90 MHz to 108 MHz, about the same as everywhere else in the world. For a list of FM stations in India, see: Avoid frequencies on the list.



[Mon Jun 30 07:40:35 2008] amblog...

convercion cb radio to irf 530 final transistor


[Mon Jun 30 07:41:24 2008] amblog...

to radio cb


[Mon Jun 30 12:49:44 2008] viewcoms.

thanku max for your coparate i will quick come a anew topic thinku illiraj55


[Mon Jun 30 23:43:04 2008] fmtx.....

Keep up the good work! It's nice to see stuff like this on the net.

Greetings from a fellow pirate.


[Tue Jul 1 05:25:05 2008] viewcoms.

Thanks, Fellow Pirate.



[Wed Jul 23 04:15:31 2008] viewcoms.

Hi Max..great story about CATradio. I run a small 5w pirate station and I too probably am 'pushing the limits' by broadcasting 8 hours a day or so! I am sure it is the local radio that will bust me if that ever happens. Luckily I live very far away from any FCC office..we'll see if that helps prevent 'the knock'...Your story will certinly guide me.


[Wed Jul 23 14:13:02 2008] viewcoms.

Thanks for the great comment!



[Sun Aug 17 10:48:19 2008] classe...

-Can the unit run without load?
-We know what bifilar means but it is not seen in the pictures.


[Mon Aug 18 06:00:33 2008] viewcoms.

Yes, the transmitter can be operated without load. The output signal will be distorted. Why would you want to operate it without load?

Bifilar? The white and black conductors shown in the photo make up the transformer primary winding. Note that the conductors are parallel with one another and that each occupies the whole circumference of the torroid core. (The secondary, under the electrical tape, is not bifilar wound.)



[Mon Aug 18 10:49:43 2008] amblog...

notify graphical representation


[Sat Aug 23 05:07:09 2008] viewcoms.

Without load incase of bad loadtuning or something. To know that the tx will survive. :-o


[Sat Aug 23 07:39:35 2008] viewcoms.

If minimal drive current (<200 mA) has been acheived and class-e operation has been verified with an oscilloscope during initial tune-up, mis-tuning the output filter will not cause excessive currents or high voltages on the drains of the output MOSFETs.

Arcing in the output filter capacitor or antenna tuning capacitor could be more troublesome. Be sure to use transmitting-type (high-voltage) capacitors in the output filter and antenna tuner to minimize the likelihood of arcing. Follow the guidelines given in the power supply section of the article to minimize the possibility of blowing the output transistors should arcing occur.



[Fri Aug 29 16:04:35 2008] amblog...

Hay! (in LV)

Ja Jums gadījumā ir zināmi mērījumi par raidītāja izejošo jaudu, kā piem. Output 200 watt apraides zona km (brīvā un masīvā vidē).


[Sun Aug 31 05:47:10 2008] viewcoms.

Hello Latvia!

I think this is asking the transmitting range, or how much coverage area, the 200-watt transmitter provides.

The answer is 'it depends'. On a clear channel at night the range could be hundreds of kilometers. On a typical well occupied channel on the upper end of the medium-wave broadcast band in the daytime the range might be 50 km. At night maybe 25 km. Maybe more, maybe less.

A guy reported listening for the station one night in mid-winter at a range of about 2000 km. Nope, didn't hear it.



[Tue Sep 2 14:31:22 2008] viewcoms.

Hi Max,
Great transmitter design (Class E 200w.)
I'd like to convert some of my LPB and Radio Systems transmitters or build new ones. I use them for carrier current operations in seniors retirement buildings. I head a not for profit group that provides senior citizens with radio listening they actually can enjoy!
Commercial broadcasters and advertisers no longer care about the baby boom generation.


[Wed Sep 3 07:35:46 2008] viewcoms.


Interesting that you mention radio for senior citizens. I deliver meals for the local Services for Seniors center. The idea had occurred to me to suggest a radio station for the housing area. (I was thinking LPFM rather than carrier current.) I thought better of it when I realized it would fall to me to implement the thing. Oh well..



[Sat Nov 8 10:03:18 2008] lasermod.

hello friend.I congrulate you.I see which it useful circuit laser.I intrest laser communacation.wi-fi&laser internet. I will be very happy hear you.feed back.


[Tue Dec 2 14:54:26 2008] amblog...

HELLO, my name is Daniel
Live IN BRAZIL AND I also happen Electronics Technician.
And visit your site to worship the projects.
Congratulations on PROJECTS.



[Thu Dec 4 06:02:53 2008] viewcoms.

Thanks for the nice comment, Daniel.



[Sat Dec 13 04:21:08 2008] classe...

This is just the info I have been looking for. Back to the bench and the junk box for now. 73's KQ2P


[Sat Dec 13 07:12:03 2008] viewcoms.

Glad you found the info useful, KQ2P.



[Sat Dec 13 07:51:42 2008] home.....

Are you connected with Max Headroom,
Jim Carter or June Carter Cash family and Nashville?



[Sun Dec 14 06:10:50 2008] viewcoms.






[Mon Dec 29 23:44:32 2008] viewcoms.

Hi Max, I was navigating within your webpages for laser sound and when I accounted for it went more than 2 hours. You are quite a guy and let me tell you, you have quite a family, nice pets and live in a very nice place. You should be proud of what you achieved in life. Most guys want a lot of things in life, they forget how enjoyable life can be when you reach a point in life when you can do simple things and nobody has nothing to do with or rattle about it. You just get out and do it, enjoy yourself and feel proud of it.

Best wishes and Very Happy and Prosperous 2009.

Wagner (Orlando Florida).


[Tue Dec 30 06:14:36 2008] viewcoms.


Thanks for the nice comment, Wagner!

Best Regards,



[Fri Jan 2 22:28:49 2009] home.....

Hi Max,
This is really nice. Take a look.
It reminds me of the way you do things, carefully and well. (And cheap!)



[Sat Jan 3 06:19:49 2009] viewcoms.

Hey, I like it! Looks great!

Thanks John,



[Wed Mar 11 07:07:12 2009] viewcoms.

[John is referring to data derived from this test setup.]

No, I haven't tweaked it at all - since that one time 2-3 weeks ago. We're seeing its stand-alone performance. Latest reading (3/11) shows it drifting even higher into positive territory. Remember that the computation result is indicated in parts per 1011, quite expanded, in other words. My plan is to let it run for awhile to see the result. I've also decided to go ahead and compute a 30-day average, for what it's worth (after I figure out how to do that).

The osc does seem to react somewhat to changes in room temp. Those few days of exceptionally warm weather last week seemed to pull the osc lower in freq and now that its cold again (-1 degrees outside this morning, about 55 in this room overnight), its again drifting higher.

I'm thinking of knitting a cozy to put over the oscillator..



[Tue May 26 14:55:49 2009] viewcoms.

Hi Max,

John here. I use to run a lowfer beacon in Bonaire, GA. Call was JDH @ 184.5 KHz. I don't know if you ever listened for it. Kyle heard it in Minn.

Anyway, enjoyed your web page. Neat articles!



[Wed May 27 05:53:17 2009] viewcoms.

Hi John,

Nice to hear from you!

I never had very good luck hearing the eastern lowfers from here in Wyoming. I heard the west coast guys pretty regularly.

Thanks for the nice comment!



[Fri Sep 25 22:36:26 2009] home.....

Hi Max,

Thanks for doing the Vref page. It looks great and says it all.

P.S. Have ya bought a Harley yet? :)


[Sun Sep 27 22:17:03 2009] viewcoms.

Hi Max
Do you have any pcb for the 200w class E.
What kind of modulator can I use.


[Mon Sep 28 05:56:18 2009] viewcoms.

No PC board. The transmitter was built using point-to-point wiring on perforated proto board.

Series class D, etc, or linear audio power amplifier, as explained under the heading "modulation".



[Wed Dec 9 23:46:54 2009] catrad...

hiks... it's so touching :)


[Mon Jan 11 15:55:27 2010] amblog...

what is your daytime range on 1710 KC?
My email is


[Tue Jan 12 09:07:06 2010] viewcoms.

I am contemplating on building a class E transmit/receiving station at home and am curious if you could tell me what your daytime range was with 200W? I plan to operate base to mobile on the bottom of the 160 meter band. Everyone usue 2 meters and I want to do it like they did before WW2. I know nightime range should be great, but what about groundwave in the daytime?


[Wed Jan 13 06:44:56 2010] viewcoms.

Hi kc5dsw74ci,

Yeah, that's the way they did it in pre-VHF FM days (I read).

The range of the 200W transmitter with the antenna shown in the article is comparable to a small local AM broadcast station. With a car radio it's about 10 miles noise-free, maybe 25 miles if you're willing to put up with some noise. Longer range might be achievable with a communications receiver at a quiet location.




[Mon Jul 12 13:28:27 2010] home.....

Hi Max
I was just looking at your project listings and it occurred to me that they don't really describe what they are about.
"Sewer-Pipe LED Projector" comes to mind.

You might consider renaming them for further clarity.



[Thu Aug 12 19:58:32 2010] home.....

Hi Max
That was about a 17 degree temp drop in 30 minutes just before noon yesterday at your place. Impressive.



[Sat Aug 14 00:51:48 2010] lasermod.

can we buy this modem


[Sat Aug 14 00:53:10 2010] viewcoms.

where can we get it? how much cost of this modem?


[Sat Aug 14 05:47:32 2010] viewcoms.

It's not available for purchase. Ya gotta build it.



[Tue Aug 31 11:33:40 2010] viewcoms.

very interesting, found your site looking for a schematic for a VHF micor PA that is being modified for fm broadcast. We were trying to decide what to call the station, our cats were walking all over the equipment so we called it "98.1 the cat" My step son did a "meow" sound and I mixed a track as the station ID. You would have thought we knew about your station to hear the story.We were totally bootleg also. I out an ad on craigslist asking any potential DJs to make MP files and I would put them on the air. I got a tremendous response and one fella said"I looked up your station on the web and Im impressed, I would like to be a employee" so I looked up 98.1 the cat and found out it is a country station in new england(we are in virginia) I about died laughing at the situation!I was running 50 watts 40 feet off the ground and got about 10 miles of coverage.


[Sat Sep 18 21:48:11 2010] amblog...

nice circuits


[Mon Sep 27 01:38:59 2010] home.....

On your Laser pointer audio modulator circuit, what exactly is the function of the points labeled TP1 - TP7? I'm thinking they are test points. Any clarification would be much appreciated. Thanks in advance.


[Mon Sep 27 07:14:31 2010] viewcoms.

The test points labeled TP1-TP7 refer to points in the circuits where jumpers and a multimeter should be connected during the setup/alignment procedure called for in the "System Alignment" paragraphs near the bottom of the web article. The alignment is necessary in order to minimize audio distortion.



[Fri Nov 26 15:54:56 2010] home.....

Hey Bro - Here's what I'd like for Xmas. Could you find "Highland Cathedral" played on bagpipes for me? Our local piper plays it in church for us and I just LOVE will too if you've not already heard it. Love, T


[Sat Jan 15 07:03:10 2011] about....

Very Cool Max Carter :-)


[Sat Jan 22 11:58:34 2011] wwvb.....

Dear Sir,
Can you tell me what is the 10 MHz voltage output in the Lucent? Thanks.
Best Regards



[Tue Jan 25 06:15:05 2011] viewcoms.

Hello Jose,

The 10 MHz output level is 5 volts peak-to-peak - TTL logic level.

The unit also has a 15 MHz sinewave output. The level is approx 10 volts peak to peak when terminated in 50 ohms.

Hope this is helpful.




[Sat Feb 12 00:44:08 2011] lasermod.

can we able to detect laser ,as soon as the laser hits the circuit?


[Sat Feb 12 05:55:55 2011] lasermod.


You might also be interested in this:



[Mon Feb 21 21:58:29 2011] catrad...

This is too good! Sure wouldn't mind hearing a broadcast. a book reading on air would be great. Good luck!


[Fri May 13 11:08:27 2011] viewcoms.

can i convert a old motorola micro base radio into a 10 or 11 meter citizen band linear amplifiers,or junk


[Sat May 14 05:37:58 2011] viewcoms.


Probably not. I'd say junk it.



[Tue Jun 7 14:21:30 2011] viewcoms.

Ah, brings back memories of my high school years of playing pirate radio (hombuilt AM 50 watt rig, then a Johnsom Ranger on 7.34MHz). A fun time was had by all. I never got the knock from the FCC, fortunately; probably lack of an efficient antenna back then.


[Thu Jun 9 05:34:16 2011] viewcoms.

Thanks for the nice comment, Bud.



[Thu Jul 7 13:56:01 2011] lasermod.

Hi Max,
Kavan here. A trivial question: electrical signals can be AM, FM, PM modulated. Can a laser, be frequency modulated? I don't think so since the output frequency is fixed (unless we use an expensive external modulator). Lasers can only work with pulses and m-ary that true or am I wrong?


[Fri Jul 8 06:09:43 2011] viewcoms.


I don't know for sure but I think you are generally correct. To directly phase or frequency modulate a laser you would need to vary (modulate) some physical aspect of the laser. Downstream phase modulators, as you mentioned, are available. These are based on optical delay lines.

Thanks for the question!



[Tue Jul 26 02:25:48 2011] laser....

I've been thinking about building the listener and mounting it in the eyepiece holder of my 10" dobsonian reflector telescope. Do you think there is anything of interest to hear from space?


[Tue Jul 26 07:25:56 2011] viewcoms.

The photo sensor mounted on a 10" telescope should work great, but the phototransistor specified in the article is probably not optimal for resolving (listening to) objects in space. Resolving power is inversely proportional the size of the sensor (or individual pixel in the case of an image sensor) - the smaller the sensor (pixel), the greater the resolving power. The specified sensor should be able to "hear" the moon and Venus, but more distant objects might be a problem. When listening to light from a distant object, you may actually be hearing the light as modulated by the earth's atmosphere. But I really don't know. Give it a try!



[Mon Aug 15 02:34:14 2011] lasermod.

where do i get all these components in MUMBAI??


[Mon Aug 15 05:12:25 2011] viewcoms.

I don't know specifically, but I suspect virtually any and all electronic components are available in Mumbai. Look for a place that sells electronic components, or you can always shop on line. Mouser Electronics is pretty good.



[Sat Sep 17 22:27:23 2011] catrad...

I remember seeing her read in the basement I always thought it would be neat to own a radio station


[Thu Sep 29 20:42:26 2011] lasermod.

what can be a good replacement for the MOSFET driver??


[Fri Sep 30 06:08:12 2011] viewcoms.

There are lots of MOSFET drivers available. Google "mosfet driver" and look for a lowside mosfet driver with a peak output current around 1 amp or more with an internal resistance in the range of 10 ohms or less. Manufacturers include Maxim, International Rectifier, Haris Intersil and others. The Microchip TC1411 is available here:
and many other places.

Other laser drive schemes could be dreamed up. The negative drive scheme shown in the article was chosen because the cheap laser pointer used has the laser diode anode connected to the pointer case (positive ground). If this is not a concern, the driver could be something as simple as an open-collector NPN transistor. The mosfet driver, coupling capacitor and Schottky diodes (U4, C7, D1 and D2) would not be needed:

If you prefer having the case of the laser pointer grounded, the simplest approach in concept (though not necessarily simple in execution) would be to wire the entire laser modulator circuit as a positive-grounded system. The connection to the laser pointer would look like this:

Note the driver is a PNP transistor.

I added a blurb in the article about this. Thanks for the question.



[Fri Oct 14 21:36:43 2011] catrad...

Ha.. Great story. Sooo- ya sang like a bird,eh?
I think the best part was your young daughters contribution. I todays world of video games and text messaging it would be great if more folks did this hands on science. But that is a dying thing with light pollution for home astronomers, electrical noise and digital hash ruining the spectrum for hams and radio hobiests etc.

Thanks again for sharing and for the web site. Next time set up in Canada! Industry Canada took two years to shut down a mega watt pirate in Toronto-even though they knew the adress and details! Infact the IC rules now have eliminated all requirment for them to find RFI interference to licensed operators etc. Theynrefuse to inforce unless it affects an emergency radio service such as police. Anything else and it carte Blanche . So come to Canada!

Hams are also affected- anything goes up hear. Operate without a license and no one cares because IC doesn't care.
Keep the site up!


[Sat Oct 15 05:24:03 2011] viewcoms.

Thanks for the comment, Greg.

For awhile there in the 1990s, the FCC in the States seemed to have the same attitude. That attitude changed as more pirates came on air and the powers that be (National Association of Broadcasters, among others) applied pressure. I'm not aware of the present situation.



[Tue Dec 13 14:14:49 2011] lasermod.

can u give me idea the alternative for tc1411??
and how to measure the right transistor i use on "Alternate Laser Drive Options"??


[Wed Dec 14 08:40:27 2011] viewcoms.

Any small signal transistor with a current gain (beta) in the 100-200 range should work. 2N2222 (NPN) or 2N2907 (PNP) or similar.

There are lots of MOSFET drivers available. Google "mosfet driver" and look for a lowside mosfet driver with a peak output current around 1 amp or more with an internal resistance in the range of 10 ohms or less. Manufacturers include Maxim, International Rectifier, Haris Intersil and others. The Maxim MAX4420 should work. See: Check the datasheet for the pinout.



[Wed Dec 14 15:09:45 2011] home.....

Hi Max
I really like the Class E 200 Watt transmitter of yours. I noticed you did not include the output capacitance of the FETs. Does this cause any problems that you have found?


[Thu Dec 15 06:52:15 2011] viewcoms.

Hi Don,

No, I didn't have any problems related to FET output capacitance but I should have mentioned it in the article. It could be significant when the tank values calculation calls for a capacitance value below maybe 10x the MOSFETs' output capacitance. This could be the case when calculated tank impedance comes in "on the high side" - over 50-100 ohms or so, ie., when high power, high supply voltage and/or high frequency is called for. The FET output capacitance should be subtracted from the calculated value. The adjustable exciter provides for duty-cycle adjustment during tune-up. This compensates somewhat for variations in component values.

As mentioned in the article, the specified FETs probably won't work well in the circuit above 2-3 MHz.

Thanks for the comment.



[Sun Dec 18 05:47:10 2011] viewcoms.

how i know which side is anode or cathode when i use a cheap laser pointer??
is it anode where positive (+) from battery connected??

thanks for reply


[Mon Dec 19 05:27:32 2011] viewcoms.

Yes. The anode connects to the positive terminal of the battery.



[Wed Dec 21 04:05:47 2011] lasermod.

I try to build the detector,,
i found that resistor R2 is hot, and voltage in resistor R1, and A (+) is 0 volt.
are my detector is right?
or something wrong??

and when i tried to put speaker in output, i heard "hiss" sound..


[Wed Dec 21 06:11:34 2011] viewcoms.

Hard to say for sure. I'd say there's a wiring error or shorted component somewhere.

Another possibility is that the front end amplifier (Q1) is oscillating. This could be the case if the circuit was not constructed using the suggested double-sided circuit board . The stage gain is very high and the grounded backside of the board forms a shield. Try some shielding around the stage.

With no input signal, a loud hiss on the output is normal when the VOL control is set to maximum.



[Wed Dec 21 06:21:50 2011] viewcoms.

if i want to use hot pointer case, how can i adjust the current regulator to 30MA?

what is the symbol (+) in hot pointer case? is it same as VDD?


[Wed Dec 21 06:31:09 2011] viewcoms.

so the receiver can not be built in single-sided circuit board? or i can use single side?
i just found out that voltage on r1 are depend on the photodiode, am i right?
i can not use double-sided circuit board because near me did not sell that, are the transmitter use the double side board to? can i use projectboard?


[Wed Dec 21 10:03:00 2011] viewcoms.

You've brought up an important point that I should have mentioned in the original article:

Yes, you can use proto-board to construct the circuits. The original boards were constructed that way. The receiver front-end amplifier and limiter-discriminator were shielded with copper foil as shown in the photos below. The shielding is necessary to to prevent the circuit from oscillating due to its very high gain. The grounded lower side of the double-sided board used on the suggested printed circuit board layout does the same.

The first photo shows the copper foil. The second shows the shielded front-end amplifier. The third shows the limiter-discriminator. [The limiter-discriminator ended up on a separate daughterboard. I ran out of room on the original board.]

Copper shielding foil. The foil is insulated on the back side. Though copper is best, any kind of metal would work nearly as well - aluminum, steel, etc. [For aluminum the ground connection(s) would need to be mechanical as aluminum is difficult to solder.] Be sure to insulate the shield.

Shielding below the front-end amplifier. I suggest you shield the entire board.

Limiter-discriminator daughterboard. Look closely and you can see the shielding on the back side of the board.

With no input signal, the output of the the receiver should be a steady hiss. It will sound very much like an FM radio not tuned to a station.

> i just found out that voltage on r1 are depend on the photodiode, am i right?

The photodiode is reverse-biased, so the voltage on the cathode should be very nearly the same as the positive supply voltage (+12 to 15 volts). Note: A photo-transistor will NOT work in the circuit. It will not be fast enough.

> if i want to use hot pointer case, how can i adjust the current regulator to 30MA?

> what is the symbol (+) in hot pointer case? is it same as VDD?

On the transmitter current regulator question: The output of the current regulator, instead of connecting to pins 1 and 8 of U4, would connect to the laser pointer case.

The + is the regulator output, 3 or 4 volts positive, depending on the setting of the regulator. Monitor the voltage across R21 and adjust for 30 mV.

[I should start a forum on the laser modulator-demodulator page to handle questions like this. Will be doing that Real Soon Now...]



[Thu Jan 5 07:24:01 2012] lasermod.

in the alignment step 4, 5, 6, and 7, where is the leads of a multimeter point to?
is it same as point 3 (when multimeter set to tp6 and tp7) ?


[Fri Jan 6 05:31:27 2012] viewcoms.




[Fri Jan 6 22:46:03 2012] home.....

Hi Max. Im Dave from Tasmania. Ive been enjoying your information on data logging with a picaxe. I notice that you have some information about haemoroids on your site. Vitamin P is the key. Its not a true vitamin but works with vitamin C to make it much more effective. Vitamin P helps the cells to have elasticity. Some berry fruits and the like contain it. If you get a multivitamin, vitamin P is called 'biflavonoids'. I suppose its easy to remember, "biflavonoids for haemoroids".

Regards Dave


[Sat Jan 7 05:27:26 2012] viewcoms.

Thanks for the information, Dave. I've never heard of vitamin P, but "bioflavonoids" rings a bell. It appears to be a controversial subject if the Wikipedia "talk" page is any indication. (

I'm not troubled by hemorrhoids. I must be doing something right.




[Mon Jan 9 21:50:21 2012] viewcoms.

Have you done any work on an ethernet interface, similar to the open source Ronja project?


[Tue Jan 10 05:28:17 2012] viewcoms.

No, I have not. The laser pointer FM effort was in response to a friend's need to feed audio to a remote radio transmitter. Ronja looks interesting!



[Tue Jan 10 18:50:24 2012] viewcoms.

I like your Sewer-Pipe LED Projector better than the Ronja one.


[Wed Jan 11 09:03:56 2012] viewcoms.

The Ronja system is obviously more sophisticated than our laser pointer/LED dabblings, but both suffer from the same limitations: attenuation of the light beam by precipitation and sensitivity to beam mis-alignment. There's probably not much that can be done about the first other than more power at the transmit end. The LED projector addresses the mis-alignment issue. The wider beam greatly simplifies alignment - at the sacrifice of range. Driving the LED harder than the pulsed 350 mA we used on our experiments - maybe up to a couple of amps pulsed - would make up for some of the lost range.

Thanks for the comment.



[Tue Jan 24 13:43:25 2012] home.....

The Koil link on your page resulted in my Microsoft Security essentials antivirus intercepting a trojan. Thought you would want to know. I'm using Firefox 9.01

73 Chris


[Wed Jan 25 05:22:56 2012] viewcoms.

Thanks Chris,

KOIL link gone!



[Fri Mar 16 03:58:57 2012] catrad...

Hi Max! Touching story!
Regards from Cluj-Napoca, Romania!
Szabo Istvan,
Sound engeneer, TVR Cluj


[Fri Mar 16 05:22:29 2012] viewcoms.

Thanks for the great comment, Szabo!



[Mon Jul 2 15:47:36 2012] about....

The frequency doubler for the 60kHz signal should have a filter preceding it, unless you always have a high signal-to-noise-and-interference ratio.


[Tue Jul 3 05:34:08 2012] viewcoms.

Re: Above comment and 2012 WWVB Receiver Mod

The RF amplifier and active antenna provide bandpass filtering at 60 kHz. No additional filtering was added. The output from the receiver's phase detector is slightly more jittery after the modification. That could be compensated for in the loop filter, but the thing seems to work OK (see graphs), so I'm not going to fool with it.




[Fri Dec 7 10:54:24 2012] home.....


Thank you for your brilliant but seemingly easy to implement work around for the code change at WWVB. I do hope that your modification manages to work its way around the WEB.

I suspect that a lot of still very functional systems, both homebrew and commercial, might be easily salvageable and kept out of the land fills.

I have noted the both NIST and manufacturers such as Spectracom have basically said that these highly specialized systems are now totally obsolete and will shortly become fully inoperable.

Mike Zydiak W2MJZ


[Sat Dec 8 06:22:56 2012] viewcoms.

Thanks for the nice comment, Mike.

For sure GPS and digital telecommunications networks have made distribution of standard frequency via terrestrial radio pretty much obsolete, and the new WWVB time code clinches it, but I wasn't ready to toss the ol' receiver just yet.

Standard time distribution via WWVB will likely also fall by the wayside eventually with the roll-out of internet-connected appliances - refrigerators, toasters, clocks. The new BPSK time code, with its signal to noise advantage over the amplitude-modulated code, should delay that eventuality.

Best regards,



[Thu Jan 10 17:14:30 2013] home.....

Am looking for any info from 1961-1962 from Simmerhausen, rothwestern, Kassel, Velmar, Germany, my mother is a german national, impregnated by an American GI, sometime in 1961. His name was Robert Lee Frazier from Texas, possibly Houston. He was married at the time with a son and daughter. I am sure that he may not be alive at this point. but I sure would like to know how many sisters and brothers I may have. I served in the AF for 8 yrs so I am a vet. Am American citizen also and have been for a long time. Live in GA. Have 1 daughter, 3 grandchildren. My Mama is still alive ( 73) still beautiful but if anyone knows any info I would greatly appreciate it. Am 50 yrs old. My name is Silke(Fischer) Sauer back in the day. Thank you!


[Tue Jan 29 11:08:13 2013] amblog...

In my humble opinion, considering the work you have done, you are my kind of HAM. I like what you have done with the older radios. I have considered doing something similar, but have yet to do so. This is an encouragement to me. Well done, very truly, well done. I am a HAM, wa2qcj, and I have a couple of old Eico transmitters about the shack, and house. Being single, who cares where it lands. I do believe that the foundations need to be considered, and kept. If we lose our foundations, then our future becomes unstable.


[Wed Jan 30 08:09:52 2013] viewcoms.

Thanks for the nice comment, Kerry.

The decade of 60s was the golden age of solid-state electronics, when most of the cool devices we use to this day were first introduced. But the circuit techniques were developed back in the vacuum tube era. A lot of sophisticated equipment was built, especially military and test equipment (HP, etc), in those days.

Best regards,



[Fri Apr 5 01:21:16 2013] home.....

Hi,can new Pixaxe 08M2 be programmed same as old 08M through serial.How do I connect 2 micro switches to 08M2??Thanks John


[Fri Apr 5 05:39:30 2013] viewcoms.


It's been awhile since I fooled with these, but as far as I know, yes. Check the specifications.

I'd say pull the input(s) high with 10k resistor(s). Connect each switch so that closing it pulls the associated input to ground. Two (or more) switches (in parallel) can be connected to a single input.



[Sat Sep 28 12:10:38 2013] amblog...

A tip of the hat your way from Texas. A real nice design and a project that looks like even I could build it. Nice work...

I'd love to hear your station but I've got a station at 1700 here in the Dallas Texas area that eats up the band... At least it is "comedy" and not, yet another "Blather Radio Outlet", or freaking Sports Radio.

I sure miss music on AM at night since KOMA changed format and call letters to KOKC and more "Blather Radio".

The ONLY AM music choice now days (or in this case nights) is WSM Nashville with 5kc bandwidth IBOC compatible AM. I get better bandwidth and sound from a telephone..Oh well..


[Sun Sep 29 05:29:19 2013] viewcoms.

Nice comment.

For sure music is dead on AM, and I wonder sometimes if AM itself will be around much longer.

WSM is covered here by KGAB in Cheyenne.

I get CBC-1 out of Winnepeg, Regina and/or Calgary. Makes reaching up and turning on the radio in the middle of the night still worth the effort..



[Sat Nov 30 15:52:43 2013] viewcoms.

I have been reviewing your circuits as I was looking for an amplifier for
a diabetes meter I use. It's a continuous glucose monitoring system that sends out
a melodic ring when my blood glucose gets too low. But unfortunately the
sound is too low to awaken me when I am sleeping so that I can suffer
hypoglycemia (very low blood glucose level) which can be very serious. So
that's how I arrived here. What I was thinking of doing is utilizing your
amp "Beep (or Siren) Power Amplifier" in conjunction with a small electret
mike with it's preamp stage. Will the unit somewhat approximate the output
signal that is captured via the mike?


[Sun Dec 1 05:39:36 2013] viewcoms.

Yes, the amplifier should work well in that application, though the output may not retain the melodic sound of the original (a very minor issue, I would think). The electret would probably work with the basic amplifier (mike taped or glued directly on the monitor's sounder) but you might get better results using the high-gain version of the amplifier circuit. The microphone and loudspeaker should be isolated to prevent feedback. Pad the volume down with a resistor (Rvol) if feedback is a problem.

Thanks for the suggestion. I added a blurb in the article about it.



[Sun Dec 1 17:25:50 2013] viewcoms.

Max, Thanks a lot for responding. I think it would be a good item for those who use the Dexcom G4 Platinum as I do and I will mention your site to them next time I contact them.

Last time I clicked 'send' without using your name nor mine. My apology for the indescretion,



[Tue Jan 28 16:22:29 2014] catrad...

I love your site, as a fellow engineer and hobbyist and maybe former pirate.


[Wed Jan 29 05:12:47 2014] viewcoms.

Thanks, fellow engineer, hobbyist and (maybe) former pirate!




[Tue Mar 11 16:45:17 2014] catrad...

What a great story. Really enjoyed it, thanks.


[Wed Mar 12 06:08:12 2014] viewcoms.

And thanks for your comment! [Readers, see: Cat Radio.]



[Sun Mar 23 17:12:23 2014] wwvb.....

Hi Max,
I have an old Tracor 599 phase lock receiver that used to work well. I have calibrated my frequency standard with it and the standard now has excellent accuracy. However since WWVB changed to phase shifting, the Tracor will not lock. Do you think your modification will work on it?

Best regards,
John Reed, KA5QEP


[Mon Mar 24 05:38:26 2014] viewcoms.


In principle, yes. It would require a study of the receiver's circuitry to determine where to install the doubler (Figure 1). A tougher issue would be reconfiguring the local carrier generator to produce 120 kHz. It might be simple, it might not be so simple. Without the receiver's circuit schematic/service manual, it would require back-engineering.

I'm not familiar with the receiver, but it's unfortunate that what looks like a fine old piece of gear suddenly becomes a boat anchor. Don't toss it out though. You never know. Someone might figure out a modification. (Click here.)




[Fri Apr 25 04:19:32 2014] viewcoms.

Max, did you ever measure the impedance at the base of the antenna? I'm looking for ohms and reactance, if you know off hand.



[Fri Apr 25 05:12:36 2014] viewcoms.

I've never measured it directly with a bridge but it roughly calculates to around 800 ohms - highly reactive (capacitive).



[Fri Apr 25 13:42:30 2014] viewcoms.

Interesting. Similar designs state around 3 ohms real, and around -550 ohms reactance (capacitive). I would like to try an autoformer type match for simplicity. It will be lossy, but the components would be cheaper and smaller, if you went the toroid route.


[Sat Apr 26 07:58:34 2014] viewcoms.

With ground resistance an order of magnitude or two greater, that 3 ohms real means the 200-watt transmitter radiates a watt or two..

Makes a good case for confining unlicensed broadcasting efforts to 3 meters (FM).  :)



[Mon May 12 05:39:38 2014] laser....

Hi,Dear Sir:
Your project is awesome,Do you need Laser diode or laser modules? We are Laser module factory,please come to me if you have any inquires,look forward your touch,thanks!-mr.jim,


[Sat Aug 16 22:56:59 2014] lasermod.

Explain about this project briefly


[Sun Aug 17 10:42:06 2014] viewcoms.

> Explain about this project briefly

This page is a catchall comment page for my website. For links to the various (mostly unrelated) projects on here, go to the home page.

If you're interested in the laser pointer modulator project, see:

Laser Pointer Audio Modulator - Laser Beam Detector/Demodulator

[Interest in this project has increased lately. I should build a dedicated comment page. Might do that sometime..]



[Sun Nov 16 11:05:35 2014] viewcoms.



[Mon Nov 17 05:17:31 2014] viewcoms.

Thanks Chris. Have fun with DCCAD!



[Mon Mar 23 21:02:15 2015] viewcoms.

Some time ago I'm working with an AM transmitter that works on 7 Mhz. The development of my team is based on his work, I used the IRFP350 mosfet which I managed to do work without problem on that frequency. The redimiento transmitter (power amplifier) has been for over 90% efficiency. The modulator used is a PWM and ultimately the power obtained in the range of 40 meters is 225 watt 28 volt power .......... as seen publication, which I appreciate very much, has served me to develop my project.


[Sat Mar 28 05:27:48 2015] viewcoms.

Hey, I'm glad it works! I didn't suppose there would be much interest in AM on 40 meters. Thanks for the post.



[Wed May 6 09:21:55 2015] viewcoms.

May I ask where you found the weather-tight box with the side latches,

annunciator whack box_inside2.jpg for the long range wireless motion detector



[Thu May 7 06:03:58 2015] viewcoms.

The box shown came from my junk pile.
New ones are available from Amazon [click: Plastic Outdoor NEMA Box] and many other places (Grainger, Crescent, etc.).



[Mon Sep 21 11:05:44 2015] viewcoms.

Hi Max, my name is Johnny from Duo Films, a film production company based in Los Angeles. I am researching how to build a large laser for audio transmission and I stumbled across website. I'd love to chat with you and ask you some questions regarding the mechanics, and pick your brain on the matter. If you are interested in collaborating with us on this project, can you please send me an email at Thank you for your time and consideration and I look forward to speaking with you.

Best regards, Johnny Lee


[Sat Dec 5 13:12:22 2015] wwvb.....

Hi All,

Thanks for your material on WWVB. Inspired by this, I modified my Spectracom 8161 successfully. I tried out with good results the MC1496 and the AD633 as frequency doubkers. I modified the reference tripler to work from 40khz to 120khz. Anyways, the unit is working properly and it appears to function as well as it before the WWVB change. The TCODE also works as expected. I may use a small uC tu re- insert the hourly phase markers as I use a chart recorder for phase tracking.

Gerhard, VE6AQO


[Sun Dec 6 12:33:47 2015] laser....

To whom it may concern,

I would love to talk to you about this experiment. I am working on some similar projects and I would love to discuss. Please contact me at


[Mon Dec 7 05:16:47 2015] viewcoms.


Thanks for the nice comment. I always enjoy feedback, especially if it's positive. :)



[Wed Jan 20 13:51:37 2016] viewcoms.

Dear Max M. Carter,

I just came across your wonderful page. I was shocked that you pay USD 5 per month in power for your machine running Apache.

I have some great proposal to you. I have hosted each and every one of my websites on - and I think my bill last time for one year was USD 38.

Furthermore they have lots of functionality which you would otherwise struggle to set up with your apache.

I think, the first year is free of charge.

My sites are,,,, and (forgot the last one, ha haha)..

Max - I love your site. I love your sharing. I work in software development for more than 34 years, and if you feel that you need some assistance in software development, let me know, maybe we can work together on something?

I really liked your radar-thing for detecting visitors!

David Svarrer -


[Thu Jan 21 08:50:54 2016] viewcoms.

Thanks for your great comments, David!

The main reason for having the server here on the premises is that it gives me total control. I can do pretty much anything I want with the machine, and it has, over the years, become entwined in my life. A recent and serious example of that is the PICAXE/Perl Dead-Man Alert System. Other applications, much less serious, include monitoring a frequency standard here and a couple of temperature monitoring apps here.

Yes, setting up Apache was a bit of a struggle, but I've not touched it in years. It works.

The cost of powering the machine 24/7 is minor compared to my other expenses. Some kind of low-powered one-board Windows (or Linux) computer might reduce the cost some, but I've not looked into it seriously; always seem to have other things more pressing.

Anyway, thanks again. I'll keep your offer in mind. I can use all the help I can get!

Best regards,




[Wed Mar 9 19:15:09 2016] viewcoms.

Dear Max M. Carter,

I was looking for ideas for the final project in my communications systems class and i´ve just found your laser modulator project which is really interesting. It would be a great help for me and my group if we could ask you some questions, if it is possible please contact me at .

Hoping for your prompt response.
Robinson Prada


[Tue Apr 12 05:52:44 2016] viewcoms.

Hi Max. Very useful sine wave generator. May I use an image generated by it in a book I am writing? I need to illustrate something called regression in statistics and don't have a package to draw a simple sine wave. Is your stuff usable in this way? I would give you credit in the book (if it ever sees the light of day) if you wish. Thanks. My email is If you don't want the bother of replying I will assume no reply amounts to consent. If you would like a credit for the sine wave just email me and it is yours.


[Wed Apr 13 05:40:35 2016] viewcoms.

R. Allen,

The sinewave images are free to use for whatever purpose. No consent or credit is required.

Thanks for the nice comment.




[Wed Aug 17 09:31:44 2016] viewcoms.

Hi Max...I just read about Cat Radio! I want to send you the "Story of KCHZ Radio", a similar experience. You'd love can I send it (pdf)? My email is


[Wed Aug 17 17:49:29 2016] laser....

Hi Max. I enjoyed reading about Cat Radio! I want to send you info about my (similar) FM radio station. How can I do that?
Hank -


[Thu Aug 18 05:20:47 2016] viewcoms.


Thanks for the nice comment!

Just send the info to as an attachment.

I'm looking forward to reading it.



[Tue Aug 30 13:22:18 2016] twist.... your eeprom programmer available? Thanks
Patrick Motley N8WNE


[Thu Sep 1 05:23:43 2016] viewcoms.


You'll need to contact the author of the article, John West. His email is

Sorry I can't help you on that.



[Fri Oct 21 16:12:04 2016] viewcoms.

Interesting story about Cat Radio, although the outcome was no surprise. It is a shame that the LPFM license requirements make it almost impossible to get a license and make a viable alternative station. Requiring that the station be non profit almost guarantees that most are religious broadcasters.

I ran a Part 15 AM station for a while. I had a coverage radius of about 1 mile. Not a lot, but very good for such low power. I wish I could have run at least 1 W or more.

I too, got ratted out by a local radio station. I had a nice, long phone conversation with Jon from the Denver office about it. I explained that I was operating legally under Part 15 and emailed details of my equipment. At the end of the conversation, Jon told me that he was satisfied that I was legal and that the file would be closed.

Later, when I moved, I took the station off the air. A year or so later, I sold it to a guy who took it up to his cabin in the mountains.

Considering the wasteland that the AM band is, I don't see the harm in allowing LPAM stations to operate. There was a proposal put to the FCC years ago about this (up to 10 W as I remember), but no action was taken (and probably never will be).


[Sat Oct 22 05:07:59 2016] viewcoms.

Thanks for the great comment!



[Tue Nov 22 09:24:14 2016] viewcoms.

Truetime Model 60-DC - 2012 WWVB Modification

I was very inspired by your write-up on the method in which you modified your receiver for the new WWVB signal. My father has an Truetime Model 60-DC WWVB receiver that is a great piece of old (phase locking) equipment. Of course it stopped working after 2012. It was a MAJOR disappointment to him and as his retirement gift, I wanted to find a way to modify it so it could work again. It would mean the world to him! This is how I stumbled on your write-up. I have a basic understanding of electronics and have designed a few basic circuits myself, but I'm no where near your level. I am at a loss on how to go about this on the Truetime 60-DC. I was wondering if you wouldn't mind glancing at the manual for the 60-DC and telling me if you think it's possible, using your method of squaring the signal. I have a link to the manual (but can't post a link on your comments page).

ANY help you could provide would be appreciated more than you know! Please e-mail me ANY time, I can send you the link to the manual.

John (W6GFY)


[Wed Nov 23 12:56:36 2016] viewcoms.


Just send the link to me at I'll have a look and get back to you.



[Sat Nov 26 08:35:33 2016] viewcoms.

From the maintenance manual for the Truetime 60-DC (PDF) that John W sent, I came up with some guidance that might be useful to those wanting to modify the receiver. Look here.



[Tue Mar 14 10:09:24 2017] viewcoms.

Max, Thanks for the laser and LED communications site. I've been trying, off & on to get an LED comm rig operating for several years. At 75 I've got to get with the program soon! Thanks again,


[Wed Mar 15 04:14:42 2017] viewcoms.

Thanks Ed,

I hope the information on there was useful.



[Thu Mar 23 21:06:17 2017] viewcoms.

Max, thank you for your article on WWVB Receiver Modification. Those AD835s are pricey but I bit the bullet and using your suggestions, I've been able to get my Truetime DC-60 going again.
One thing that I've noticed, however, is that your additional modification (replacing the 10k resistor with 100k and piggybacking 2.2Mohm across the 680k resistor) does not work for me. The AGC voltage drops to -220mV and completely shuts down the input amplifier... once those parts are restored to their original values, the AGC goes back up to about -45mV and I'm "hearing" the WWVB once again.
Keep in mind that I have one of the original DC-60's running here with board numbers starting with 85-...
I'm located in the Toronto, Ontario area and normally the WWVB signal here is around -70 to -75 dBm. I'm curious if this modification change was intended for those living closer to Ft. Collins?
Anyway, bottom line is I'm happy my DC-60 is working once again. Thank you once again.

vy 73


[Fri Mar 24 04:12:32 2017] viewcoms.

I enjoyed your Cat Radio history, and your AM articles.

Vy 73 de
OZ7LS Lars


[Fri Mar 24 05:49:51 2017] viewcoms.

Very interesting, Alex!

Yes, that is precisely the case, though maybe for a slightly different reason. WWVB radically upped its radiated power about 10 years ago. My correspondent John W, located in California, experienced the overload problem described. In that case the revised version of the mod shown on the web page was beneficial.

I suscpect you would have been OK simply clipping out the 2.2 meg resistor, but hey, you can't knock success! Glad you were able to got your 60-DC up and running, and thanks for your feedback. You've passed on some very useful information!



[Fri Mar 24 06:39:59 2017] viewcoms.

Thanks for the comment, Lars. I love it when folks actually read and enjoy what's on here!




[Tue Aug 15 20:48:44 2017] viewcoms.

Hello Max I enjoyed reading Cat Radio story while I was here in the city, the island have no AM radio station. I want to build like what you do, but in 1611 KHz dial.. Can you help me identify on what part I need to modify aside from the antenna?

Hoping for your prompt response.
Elmer Isla

Dalupiri Island,
Municipality of Calayan
Province of Cagayan


[Wed Aug 16 10:37:28 2017] viewcoms.

Hi Elmer,

The transmitter circuit(s) as shown probably would work with little modification at 1611 kHz. You might consider substituting type STP20N90K5 for the specified IRFP350LC MOSFETs in the final. I have not tried these, but the specs look pretty good.

Be sure to read the posted comments of previous builders. Their experiences are educational. Expect to do some experimenting (especially if you substitute the MOSFETs). An oscilloscope is required to properly adjust the transmitter.

Good luck.



[Mon Sep 4 19:19:30 2017] viewcoms.

I am seeking low-band radios on 25 Mhz. These were used by oil companies for exploration. No one makes that range any more. Please let me know: WD8BVL (


[Sun Sep 17 19:03:32 2017] viewcoms.

Hi - thank you for your information about WWVB timing receivers. I was just given a True Time 60-TFR; is there any chance you might have a link to a manual or other documentation? Alternatively, do you know anyone looking for one?


[Mon Sep 18 05:32:03 2017] viewcoms.

I don't have any information on that receiver. You might drop a note to John van Groos. His dad was president of True Time. johnwvg at gee mail etc.



[Mon Sep 18 14:10:28 2017] viewcoms.

Thank you Max - I have followed up with John.



[Thu Sep 21 00:49:20 2017] viewcoms.

Hi Max,

John did not have a manual but had some very interesting product descriptions and specs. I am finding it harder to think of getting rid of the 60-TFR and easier to think of modifying it, especially with the increased WWVB power level making antenna construction easier. Rather than doing all the work at 120 KHz what do you think of following an analog squarer with an analog square rooter so that all the work is done at the original frequency?



[Thu Sep 21 07:30:31 2017] viewcoms.

Hi Andrew,

Without knowing the internals of the 60-TFR, it's hard to say for sure. Modification of the carrier generator in the 60-DC was relatively trivial, requiring only a bit of rewiring to make it produce 120 kHz. I did explore the idea of following the squarer with an analog divide-by-two. In addition to requiring a second multiplier chip and associated components, the circuit turned out to be way too fussy. (I hadn't thought of the square rooter.) The trick is maintaining the amplitude modulated time data riding on the signal through the processes. If you decide to pursue the idea I would be interested to see the results of your efforts.



[Thu Oct 5 14:40:48 2017] viewcoms.

Hi Max,

Have you tried adding a squelch? We use these circuits in a demo for the Texas A&M physics festival, but when showing that the laser is actually what's transmitting the signal (by blocking the beam), but it's pretty miserable to have so much noise from the speakers when we do. Any recommendation?



[Thu Oct 5 15:00:06 2017] viewcoms.

Oops, I guess this page is not just for the article I was viewing. I'm referring to the laser audio transmitter circuits in the previous question.



[Mon Oct 9 14:26:59 2017] viewcoms.


Forgive the slowness of my response. I usually try to check this forum once a day, but haven't been able to lately.

No, never thought of adding a squelch. I'll give the squelch idea some thought and post a circuit if I think of something simple. [See below]

Glad to hear the circuits are useful in your education efforts!


I presume you're demonstrations take place at short range. Try adding the resistor, circled in red below, to pin 1 of U2. Try lower values if 1 meg doesn't work, or you could use a pot to make it adjustable:

Let us know if it works.




[Mon Feb 5 13:17:34 2018] viewcoms.

dear max

I need to transfer with AM band 32Kbit

data once in every day for 100 km distance

please advice me on which tech I can use


[Tue Feb 6 08:11:12 2018] viewcoms.

FM stations transmit data - song titles and the like - on a subcarrier. I don't know of any technology currently in use that does likewise for AM, but I'm not very well informed on the subject. Directly phase-modulating the carrier would be one way to do it. It would be helpful if you could post more detail on exactly what you want to do.

Not much help I'm 'fraid. Sorry..



[Fri Mar 2 03:03:23 2018] viewcoms.

Hi The HG 303 A VFO (eg V-10) will take it down to 160m will it not? Why ruin the set to run it at the least used ham band? I just don't understand that sort of Ham butchery....which has ruined so many scores of thousands of sets (including the BC 348..)


[Fri Mar 2 05:24:59 2018] viewcoms.

Check out An AM Transmitter Modification and Construction Project for background on the project. Quoting that article, "This ain' no restoration project here." I took an old piece of ham equipment destined for a landfill, repaired and re-purposed it as a pirate AM broadcast transmitter on 1710 kHz.

When you think about it, everything is destined for a landfill. Hm..



[Sun Apr 8 11:13:07 2018] viewcoms.

Thanks for the PRAL calculator What a great resource for Sony one who had a kidney stone and doesn’t want another!
Found a bug in the calculator. A comma kills the result. 2,497 in the Potassium number doesn’t give the same result as 2497!


[Mon Apr 9 05:32:39 2018] viewcoms.

Not really a bug. The calculator treats all commas as decimal points.

Thanks for the nice comment.



[Fri Dec 21 12:15:43 2018] viewcoms.

I found your blog while looking for a driveway sensor with low false alarms that can survive AND operate in Canadian cold weather.

I have to tell you your ideas are remarkably clever. I myself am a pretty intelligent woman living on my own ion the bush. But, I must admit, after about the 2nd paragraph you went WAY over my head. And though I am SURE I could learn to create the same inventions you've made, I simply don't have the time to sit down and learn all this stuff you seem to have knowledge of. However, I get the concept, and if I ever get time I would not mind trying to make something like that.

The above dead man all=arm is GREAT, and I WISH I had something like it. I do not get cell service at home and for years did not even have a land line. So, I often receive texts over WiFi telling me my friends or family are about to send OPP to my house. And actually they HAVE done it.(My satellite dish was covered in snow so I had no WiFi, my friends in USA contacted friends here in Canada on freaking Facebook, and they all decided I must be dead or fell off the roof and was lying in the snow pile next to the house. Of course none of them knew the snow was piled so high i could literally STEP off the roof onto the pile. Embarrassing that's for sure) I would love a way for them to be able to know I am alive without camera access to my home and without giving up my personal affairs. However your idea is still reliant on WiFi or even cell phone use, both of which aren't reliable here. My new home phone is also not 100% as it sometimes doesn't work when hydro is out. So, for now I guess I am stuck with occasional visits with the Opp.

Comment about the rattlesnake in your house. That's interesting and a bit scary. But, how do you like this? I was gone for a month and came home and found a dead three legged baby weasel IN MY HOUSE!! I assume he lost a leg in one of my mouse traps. But, I STILL have no idea HOW it got in the house to begin with. I wasn't born in Canada, so i had no idea about weasels. I thought I had a ferret in the house! He was about that big! I spent weeks afraid I would walk outside and find "Momma Weasel " standing at the door with her boxing gloves on asking me to give her kid back!

I wish you luck, and I will keep your hemorrhoid advice in mind!! :-)


[Sat Dec 22 08:19:52 2018] viewcoms.

Thanks for your very interesting comments.

Yeah, the "dead man" application, as designed (and mentioned in the article), has a limited mission - to alert my daugher if I should drop dead or become seriously disabled. It depends on having more or less reliable electric service, as well as a connection to the internet.

The application here runs on the computer that hosts this website, an old WinXP desktop PC. The machine is UPS-protected and runs 24 hours a day. There's probably a program or device out there that could wake the machine a couple of times a day from standby mode to poll the dead-man interface, but it would be superfluous in this case since the computer runs 24/7 anyway.

The rattlesnakes hanging around here take advantage of the large prairie dog, rabbit and vole populations. My barn cats help keep those populations down, which helps to keep the rattlesnakes away. I think I need more cats..

Take care,



[Wed Feb 13 16:58:09 2019] viewcoms.

Hi Max,
It's been awhile since we communicated last so I figured I'd give you a shout. Still enjoying retirement - six years last month. I found a couple of things that keep me busy. I've been a snow-spotter for the NWS for 4 years now. It involves taking measurements of new plus existing snow and calculating moisture content. I also volunteered my services for the local civic assoc in assorted capacities. Currently, I'm the treasurer. Lastly, I trained as a dialysis caregiver so I could supervise my wife's 4-times weekly dialysis treatments. We have the machines (2 of them) here at home in a room we've dedicated to that purpose. Lastly, we joined the YMCA in early 2018, so we swim 4 days per week. That's about it! I have time to read the occasional book and walk the dog if weather permits.

So how are you doing? Winter in Wyoming is no picnic I'm guessing? I was looking at the websites dedicated to military bases in Germany recently. I noticed Ayers is now some sort of trucking center. Also, I found some info on Sembach which claims it's now an Army post. They turned the flight line over to the German economy and they've removed the runways, etc. Things change. Don't be a stranger.

I was going to e-mail you but seem to have lost a lot of my older e-mail addresses. If you want to send it along, I promise I'll keep in touch more often. My e-mail is
Hope to hear from you soon.

Al Luckey, your Delaware frient


[Thu Feb 14 08:08:40 2019] viewcoms.

Hi Al,

Nice to hear from you again. It sounds like you're keeping busy in retirement. Sorry to hear your wife is undergoing dialysis. That alone would keep anyone busy if you were having to go to a dialysis center.

Still coasting along here, still healthy. Will click over 19 years of "official" retirement this year. I lost my meal delivery gig at the local senior center. They decided to do away with the volunteers and went with an employee driving a dedicated vehicle owned by the center. Most of my time during the warm months is spent here on the spread, irrigating, mowing, and lately working on the house, painting and fixing. I'm not there yet, but the time is coming when I'll have to move and will need to unload this place. Keeping busy in the dead of winter is a little tougher. I mostly fool around with stuff on my bench - some of those activities are shown on the web site. I do manage to walk 2-3 miles every morning unless it's really cold and really windy.

Yeah, I see that they've scraped off every building on "the rock" and replaced them with warehouses or something. The only exception is the chapel. It still stands, called "Ayers Chapel". I wonder who it serves? The local German population maybe. The runway at Sembach doesn't seem to exist anymore.

Sending you my email address.



[Mon Mar 18 20:14:23 2019] viewcoms.

anybody have an orban 9100 or 9200 am processor they want to part with?


[Sun Apr 7 11:03:40 2019] viewcoms.

Thanks for the work on getting WWVB working for me again! I will give your circuit a try on my "time machine".
love the web site, especially like the after picture of the rattler.
Take care,


[Mon Apr 8 06:16:05 2019] viewcoms.

Thanks, Todd.



[Fri Jun 7 10:56:33 2019] viewcoms.

I found "Characterizing the Antenna" to be very informative. Can the system be modified to use an antenna analyzer (MFJ, Rig Expert or similar) instead of a signal generator and scope? I am interseted in characterizg antennas (wire) of unknown impedance and reactance. Thanks for any information.


[Sat Jun 8 05:29:00 2019] viewcoms.

Thanks for the nice comment on the page.

Antenna analyzers (from what I read on Wikipedia) incorporate an impedance bridge, signal source, tuning components and measurement device (scope, meter, etc.) into one integrated unit. They are one-port devices - the antenna to be characterized is attached to the port. The fancier units automate the measurement process. If you have an antenna analyzer, you have everything you need to characterize your antenna, it would appear - no need for any external equipment.

Hope this is helpful.



[Tue Jul 9 08:19:00 2019] viewcoms.

Hi Max. Thanks for the page! We have a lot in common.
I built an AM transmitter with two 807 tubes in the final. It works, but doesn't seem to have the power as advertised. I was wondering if you could take a look at the diagram and see if you notice any red flags? The first thing I noticed is the lack of an rf plate choke on the 807s. Google search "tibet sound system" 807 schematic. Make sure you include the quotation marks ust as I typed it. It will be the first image in the Google image search. Should have two 807s, two EL84s, one 12AX7, and one EF80. If you need any other info, send me an email. Thanks for your time!


[Wed Jul 10 05:45:41 2019] viewcoms.

The circuit utilizes screen modulation, in which case PEP and carrier power (CW) are the same: 60 watts CW = 60 watts PEP. The circuit's "AM rating" will be 15 watts (60/4). The author has misstated PEP. You can check this with an oscilloscope and dummy load.

Hope this is helpful. Write again if you need further clarification.



[Wed Nov 13 22:12:40 2019] viewcoms.

Hi Max,
looking for IR-com I came to Your home page. Thank Your for this "broad band lot of stuff", including samoyedes and cats. I had dogs, will have again SURE. Compact "red light" on bread boards, so my plan. Reading Your stuff with great joy. 73 and all the best, from norbert, germany, south west, DE.


[Thu Nov 14 05:11:39 2019] viewcoms.

Thanks for the nice comment, Norbert.  :)



[Tue Feb 11 06:55:45 2020] viewcoms.

Good morning Max! I read your article about the laser pointer to transmit audio and I was very interested in assembling one, but I wanted to assemble using a green laser, would it be necessary to change anything in the circuit diagram for it to work with the green laser?

Roni Carvalho


[Wed Feb 12 07:26:58 2020] viewcoms.

Hi Roni,

The laser pointer driver circuit is designed to directly drive a cheap laser pointer, including any internal current limiting resistor that might be present, but without internal active current regulation. If you can open the green pointer and determine that an active current regulator is not present, then the circuit shown should work OK.

I'm not sure of the current drive requirement for a green laser - which is actually an infrared (IR) laser followed by a frequency doubler - but it's probably similar to a red laser, around 30 mA. You may have to experiment with the current setting.

For what it's worth, I'm not sure a green pointer offers any advantage over a red pointer for audio communications.

Hope this is helpful. Let us know how it works. :)




[Mon Feb 17 11:49:08 2020] viewcoms.

Hi Max,
Thank you very much for your attention in responding to my comment, I set up the laser pointer driver so I couldn't use the multimeter, I followed all the instructions and it didn't work, I also realized that the receiver is capturing a radio station and is using a lot of interference , do you have any idea how i can solve this problem? Do you have an e-mail or other place where you can be posting as images of the circuit I put together, so maybe you can help me.

Roni Carvalho


[Tue Feb 18 05:40:04 2020] viewcoms.





[Sat Feb 29 13:47:34 2020] viewcoms.

I'm about to build your FM laser communicator and I noticed the tank circuit of the receiver has a resonant frequency of 156KHZ. If our carrier is 75KHZ, don't we want the tank to resonante at that freqency? Ritchie Williams


[Sun Mar 1 05:21:17 2020] viewcoms.


The capacitance of the photo diode and the interconnecting wire pair come into play. It's not a high-Q tank. I think I derived the values experimentally. (It's been awhile.) Feel free to experiment with the values.

Good luck,



[Wed Apr 1 16:47:26 2020] viewcoms.

Hi Max!

I tried to use the green laser but it was not successful, so I'm using the same red laser. I had a doubt, is the circuit applying Nayguist's theorem? where I connect the oscilloscope probes to view the signal before and after sampling. Thank you very much in advance!

Roni Carvlho


[Thu Apr 2 07:04:57 2020] viewcoms.


Yes, the modulator could be thought of as an analog to digital converter with a sample rate of 75 kHz. Its output is a frequency-modulated 75 kHz sub-carrier. The demodulator in turn could be thought of as a digital to analog converter - the 75 kHz sub-carrier goes in, the analog signal comes out. So, yes, use an oscilloscope to adjust the modulator, as shown under System Alignment / Fine Tuning / With Oscilloscope. A sine wave generator will also be required.

Good luck,



[Thu Apr 2 16:41:33 2020] viewcoms.

Hi Max, thank you very much for your attention you are very helpful and this is a difference that few people have. To align the system using the oscilloscope I need to connect the modulator and demodulator as a mast in the design, but do I need 2 resistors, 1 resistor of 10 Megas and the other of 100 omhs?

Roni Carvalho


[Fri Apr 3 08:32:23 2020] viewcoms.


No, it is not necessary to use the Figure 3 connections and resistors. You can simply set up the modulator and demodulator on your bench and use the light beam from the laser to pass the data from modulator to demodulator. The Figure 3 connections might be more convenient, but are not required.



[Sun Apr 5 19:07:05 2020] viewcoms.

Boa noite Max!

Como sempre muito prestativo, muito obrigado.


[Fri Apr 10 11:18:52 2020] viewcoms.

Good night Max!

As always very helpful, thank you very much.

Roni Carvalho


[Mon May 4 22:17:14 2020] viewcoms.

Hi Max, Thank you for your pendulum clock. I will show it to my wife who thinks I'm the only "enthusiast" working on an anachronistic time keeper!
My pendulum uses a 1m borosilicate glass rod that isn't affected by temperature or humidity (and was quite inexpensive). My control circuit uses optical position sensing and a coil to drive a small neodymium magnet located on an aluminum wire rod below the pendulum bob. Tuning took ages so I now use a linear stepper motor and controller with remote control with an auxiliary mass. Having gotten the period about right (2 seconds), I just power up the controller and move the auxiliary mass up or down and compare the result against NIST Time. The whole sysytem fit nicely in an IKEA curio cabinet so it looks a bit like a long-case grandfather clock (and I don't need to worry about inquisistive kittens). The time display is a quartz clock with brass gears. I removed the battery and driver circuit and drive the motor from a CMOS and linear IC circuit. The display sits on a the brass base from a German KUNDO Anniversary torsion clock. Building clocks is no way of demonstrating your sanity to your kids!!


[Tue May 5 08:36:25 2020] viewcoms.

Thanks for your interesting comment. Judging by this site's daily access log, there are a few others in the world that share an interest in the arcane hobby of pendulum building.

I would be interested in seeing a photo of your pendulum clock if you'd care to pass it along, at




[Wed Nov 11 14:50:05 2020] viewcoms.

Hi Max !

Just got a laser pointer and was curious if anyone had experimented with long range comms using them. 'Lo and behold, I found your site. Thanks !

We have some obnoxious dogs next door and I've been "jamming" them with ultrasonics. Pretty sure it doesn't hurt them, just disrupts their conversation with other dogs in the neighborhood. I'm told ultrasonics can be handy for discouraging mice in structures ( small ultrasonic emitters that fit in the outlets are available ).

You'd have to keep them away from all your cats, though !

Regards !


[Thu Nov 12 05:12:00 2020] viewcoms.

Thanks for the comment, Jeff. For sure, dogs often strike up a "conversation" around the neighborhood. One dog starts to bark for whatever reason and soon every dog within a half-mile radius joins in. I've seen articles about ultrasonics repelling various critters. My cats, along with the owls, hawks and rattlesnakes around here, do a pretty good job of keeping the mice population down.

Glad you enjoyed the laser article. It's great to get feedback, especially if it's positive!

Take care,



[Fri Mar 5 17:17:21 2021] viewcoms.

Hi Max, did you receive Bob Guidry's email reference Randy Pousson. I tried sending to your email but it bounced back. Hope you're doing well. Not so bad here lately. I did get engaged recently, though.


[Fri Mar 5 17:19:01 2021] viewcoms.

I forgot to sign my's Al Luckey Max. Sorry about that...a senior moment, I guess.



[Sat Mar 6 05:26:21 2021] viewcoms.

Hi Al,

Doing well here. No, I did not receive an email from Bob Guidry (??).

is good.



[Fri Apr 2 14:25:50 2021] viewcoms.

You've got a really interesting site. I've really enjoyed perusing it. Google sent me here when I was looking for info on electromagnetic pendulums. I turned your light on and off. :)
Keep up the good work.
Don in Tacoma, WA


[Sat Apr 3 05:31:10 2021] viewcoms.

Thanks Don. Appreciate the nice comment.



[Tue Nov 30 11:08:49 2021] viewcoms.

Max, what BTU (or energy) value did you use for propane?


[Wed Dec 1 06:03:54 2021] viewcoms.

I went back and looked at the code. Looks like I used 92336 BTU/gal, which might be on the high side. A google search reveals values as low as 91000. Not sure where I got 92336. (?)



[Wed Dec 2 07:24:26 2021] viewcoms.

Max, per US standard common heating propane known as HD-5 has a typical heating value of 90500 BTU/gallon (excluding efficiency factor). Thanks for checking this.


[Fri Dec 3 07:32:46 2021] viewcoms.

I made the correction. Thanks for writing.



[Sat Mar 19 11:29:01 2022] viewcoms.


You wrote a series of articles "BPSK Receiver Explained" in the 1990 issues of The Lowdown from the Long Wave Club of America. Would you have a pdf or word copy of those articles? I know this design would be implemented with a SDR radio and microcontroller today but I find the concepts easier to follow in this hardware implementation.
Regard's Mike N2MS


[Mon Mar 21 07:30:05 2022] viewcoms.

Thanks Mike. I'll see if I can find those articles.



[Thu Mar 24 08:32:17 2022] viewcoms.

Any luck in finding copies of those articles?

Mike N2MS


[Sat Mar 26 05:19:45 2022] viewcoms.

Not so far. I'll keep looking.



[Sun Apr 3 06:19:49 2022] viewcoms.

Hey Mike,

I FOUND those articles! Will photograph and post them here.

Stay tuned.


BPSK Receiver Explained


[Tue Apr 5 10:45:48 2022] viewcoms.

Hi Max,

Thanks for the article. I printed them as a pdf. Any other technical articles would be appreciated. I have been donating my technical books and magazines to the InfoAge Museum in NJ and will donate my collection of "The Lowdown" to the museum.

Mike N2MS


[Wed Aug 17 19:23:04 2022] viewcoms.

This is an enjoyable story that we can all relate to. It reminds me of the story in an old issue of PE (or was it EI?) about "WBBH: THE STATION WITH EVERYTHING -- EXCEPT A LICENSE". Thanks.

Bruce Zuckerman

KN4IDF; good on QRZ


[Fri Aug 19 05:06:30 2022] viewcoms.

Thanks Bruce.



[Thu Mar 21 18:27:24 2024] viewcoms.

i'm reading this story almost 19 years later, still enjoyable and yes i still wonder in today's digital word if CAT Radio exists online.
Best regards from Santiago Chile


[Fri Mar 22 05:45:17 2024] viewcoms.

Yep, 19 years ago is about right. The Cat Radio story was one of the first additions to the web site. Unfortunately, CR does not exist online.

Thanks for writing. :)



[Tue Jul 9 19:16:07 2024] viewcoms.

Great website!! Thanks for the cat radio conversation story. It was very informative. And all the cat and dog pictures 🖼️


[Wed Jul 10 06:07:54 2024] viewcoms.

Thanks for the nice comment!



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