I have long maintained that building a CW Transceiver was more difficult than building an SSB Rig. The main issues were the offset and handling the changeover. Without saying the 2.7kHz wide SSB filter would have to go.
A way to skirt that problem is to build a Trans-Receiver. This is what this project did and consists of a separate Receiver and separate Transmitter with the only common elements being the VFO and TR system.
You have to love SSDRA (Solid State Design for the Radio Amateur) as some of the project elements came directly from that publication.
The first is the strong amplifier (2N5109) following the Receiver Mixer (TUF-1) and a 3dB pad between the 2N5109 and the 9MHz homebrew crystal filter. For my friend N2CQR, this actually has a 5 MHz Analog VFO that doesn't drift!
The TR Circuit (as found in SSDRA) uses the NE555 which also was used in my KWM-4. You essentially key the NE555, for semi-break-in and it supplies a timed voltage to the TR relay and more importantly to the Transmit Mixer, an NE602 which has a 9MHz Crystal on pins 6/7. This arrangement lets me transmit the offset frequency. A healthy 2SC2075 puts out 3 watts on 20M. The audio amp can do over a watt, and you can hear that on the video.
The final Flash in your Face is the use of the National Velvet Vernier drive mechanism. The frequency chart shows the VFO is linear and can be reset to any frequency you want in the tuning range.
A 20M QRP CW Transceiver
Wooden Box Radio
The story behind this rig was an article that appeared in one of the radio magazines where a ham built a transmitter and receiver in a wooden box, and he would take that in the field for portable operation in the late 50's early 60's. I thought if I could ever find a wooden box then I would build one. The earlier radio had tubes and this one is solid state.
As it turns out the XYL bought some aroma therapy crap that came in a nice wooden box -- suddenly the light bulb came on!
Had I really thought carefully about this the rig it might have become a product from JES Systems.
Part II
The terrible truth that stands out about this rig are the short comings of this project! This design as cool as it, violates one of my cardinal principles of how I build stuff today. Both the Receiver and Transmitter are built on a single circuit board with the wiring done under the boards. This is not good for doing experimentation, servicing or making upgrades!
But this was built about 15 years ago and so today's perspective is a lot different where the circuit elements are built in modules. Want a change, then just swap in a new module.
Today we have Surface Mount components and things like Arduino's and Si5351's at our disposal to build our rigs. The NE602 in the Receiver would be replaced with a ADE-1 and of course the BFO would ride along with LO.
The NE555 would be just a call function in the sketch. The MPSH10 would now be a BFR106 and the 9 MHz Filter perhaps a 6 pole with a BW of say 1100 Hz.
All wiring would be on top of the boards to facilitate servicing and maintenance. The National Velvet Vernier would give way to a less than 1-inch square Color TFT. Lastly a smaller wooden box.
The offset scheme in the transmitter using the second NE602 could be done with the third clock on the Si5351, and the mixing done in an ADE-1 -- all automatic and all done in the Arduino sketch.
There is a huge difference between the rigs of old and what can be done with today's technology. In the meantime -- WYKSYCDS!
73's
Pete N6QW