80m/20m Receiver

The various modules were built using ground plane construction on copper clad PC
board. Here are the basic sections of the receiver:

-RF filter stage, relay switchable between 80m and 20m
-Doubly balanced mixer
-Analog local oscillator, with very fine, smooth tuning; one turn of the dial covers about 7 kHz.
-Post mixer bipolar amp
-1st IF filter: 2.1 kHz wide, 9 mHz Yaesu SSB filter
-2nd IF filter, relay switched 400 kHz wide, 9 mHz, homebrew CW filter,
-IF amplifier section in sealed cast box, containing, low gain JFET amp, two stages of MC1350P
IC amps (gain control is applied here), and post amp
-Outboard 9 mHz tail-end filter
-Product detector (doubly balanced mixer)
-One transistor BFO feeds product detector
-The AGC is audio-derived, with a full wave detector. This controls the MC-1350P ICs
and is used to drive the S-meter.
-Audio section: audio diplexer, two stage audio amp, with IC power amp

- An external Hi-Fi speaker is used.

The receiver is built in a junked Galaxy V case and built on the stripped chassis. I hand calibrated the drum dial, that is mounted on a plastic container. The scale for 20m is such that it tunes backwards compared to 80m. Here is a view of the transmitter. The transmitter was built using ground plane construction on a copper clad PC board. The ground plane construction looks primitive but works great. The circuit board is mounted on a scrap of plywood with two small pieces of aluminum for the front and rear panels. A cookie sheet bent into a U shape provides the top for the cabinet. A few coats of black crinkle paint and some labels transformed the set into the unit you see here. The output of the transmitter uses an IRF-510 HEXFET, operating on 20+ volts. The rest of the transmitter uses 12 volts. A single crystal at 3.547 mHz is used, with minor frequency change available from a variable capacitor in series with the crystal. The transmitter puts out about 12 watts. The receiver plugs is connected to the lowpass filter of the transmitter through solid state switching, so no manual switching is required between transmit and receive. The paddle is one I built from a kit by W5JH. It is solid brass, very smooth and beautiful! For more info on the paddle, click here.