"The Motley Special" aka "The Red Lantern"
Click HERE for the schematic.
I was poking around DIGIKEY a while back when I stumbled onto crystals they had for 3.932 MHZ.
We have a net (better called a gathering) up here called "The Motley Group" which meets nightly on 3.933 MHZ.
I picked 4 of the crystals thinking that I would make a cw rig like the PIXIE that AL7FS talked
about on his great QRP site.
Bill M0HBR and I have been talking about DSB/SSB rigs on SolderSmoke he encouraged me to give
building a simple SSB rig a try.
Poking around I found the circuit for the PSK Warbler designed by Dave Benson aka NN1G/K1SWL
of Small Wonder Labs.
I took the basic idea of a crystal controlled SSB rig like the Warbler which has a transmit chain
with a crystal ladder filter to remove the unused sideband.
Basically this rig contains a SA612 (NE602) oscillator and mixer rubbered up slightly from 3.932 to 3.933 MHz
The mixer is fed audio from a microphone/opamp and produces double sideband.
The mixer is followed by a little two crystal ladder filter to lop off the upper sideband.
The (now) LSB signal is fed into a chain of 4 transistor amplifiers to get the level up enough
to drive a push pull set of IRF510 MosFets.
The MosFets are followed by a 7 element lowpass filter which is connected to the antenna.
The receiver is very simple 2 IC direct conversion receiver made from a SA612 and an LM386.
The basic design is from chapter 1 of "Experimental Methods on RF Design".
The SA612 mixer is connected to the transmit oscillator as an LO and to an LM386 as an audio amp.
The output from the LM386 is connected to a powered SoundBlaster speaker.
T/R switching is QSK with the receiver directly connected to the TX lowpass filter through
a small capacitor and back to back limiter diodes. The LM386 audio output is shorted
to ground through a 2n7000 when PTT is pressed.
Im sure that improvement can be done to the transmit chain but this is what I had to do to get to work
I will post the as-built schematics and notes soon.
