Communications Receiver

I designed and built this solid-state SSB and CW amateur band (80m-10m) receiver in the early 1970s. It features linear dial calibration, with 1 KHz readout, a hang AGC, dual selectivity, and 5 watt audio output stage.

Circuit Description: The design is rather dated by today's standards, but was state-of-the art in its time. Signals from the antenna pass through two stages of bandswitched preselectivity (using toroid inductors), are amplified by a MOSFET r.f. amp and then converted to 9 MHz with a hot-carrier diode ring mixer. The MOSFET VFO tunes 6.0-6.5 MHz and is premixed with a bandswitched crystal oscillator to provide high-side injection into the first mixer. Filtering is provided by KVG 2.4 kHz and 500 Hz crystal filters. After IF amplification using MC-1590 ICs, the signal is detected with a product detector using an MC-1596 IC. Audio-derived AGC is generated using a sophisticated Plessey SL621 IC, and has fast (100 msec) and slow (2 sec) hang times, selectable from the front panel. The detected audio is amplified by a five watt push-pull AF amplifier, which uses op-amp drivers and a push-pull transistor output stage. The power supply provides regulated +12V and -12V.

Construction: The circuitry is built on homemade double-sided printed circuit boards. The cabinet and trim-ring are homemade, and the front panel is aluminum covered with black vinyl. The cabinet has a baked enamel finish, applied by a typewriter repair company. The dial is an Eddystone 898.

The receiver construction and circuitry is described in detail in the last several editions of The Radio Handbook, edited by Wm. I. Orr, W6SAI.