Photos
14-watt FM Stereo Broadcast Transmitter
- North Country Radio's MPX96 gets some help -
The blue thing on the right is the exciter/stereo generator. The gray thing is the 14-watt power amplifier.
Exciter/stereo generator interior.
The modified MPX96 is the larger board in the center. The input audio filter/pre-emphasis network is the smaller board on the left. The modulation limiter is the upper board. The unit's carrier output power is about 2 milliwatts.
MPX96 Mods
MPX96 Adjustments
Power amplifier interior.
The intermediate power amplifier (IPA), a modified Ramsey LPA-1, is under the shield on the left. The power amplifier, salvaged from a Repco VHF land mobile transceiver, is the small board in the center. Components of the unit's 13.8-volt power supply occupy the balance the of interior space.
The power amplifier with the IPA shield removed.
The IPA has a gain of about 27 dB. It amplifies the carrier from the exciter to a level sufficient to drive the power amplifier. Both the IPA and PA stages are tuned with lengths of coax transmission line (the black coils). The operating frequency is 99.7 MHz.
Modified LPA-1 schematic
The exciter/stereo generator and power amplifier viewed from the rear.
A switch on the rear of the exciter/stereo generator selects the unit's operating mode - mono or stereo. The small aluminum box houses a 120 MHz low-pass filter.
Horses
