Building the W7ZOI, 20M SSB Transceiver
4/10/28 ~ Comment: this rig is only one of three that I have built that is fully SSB and CW capable. with the other two being the KWM-4 and this rig's twin brother. Unless you provide capability for narrow signal filtering then operating CW using a wide SSB filter (700 Hz as compared to 2.1 KHz) does not make for a competition grade rig. OK for casual contacts; but not one for a true CW enthusiast. Today I would look at a diode steered two filter scheme and like in the KWM-4 and the W7ZOI rigs use a separate CW keyed crystal oscillator (or the third clock on the Si5351).
Since I am not a CW enthusiast nor always QRP my main thrust is SSB and to have linear amps on the output. Hats off to those who like QRP + CW. There is room in the hobby for all.
In 1999, I decided to build the W7ZOI 20M QRP SSB Transceiver that appeared in a two part article 12/89- 1/90 in QST. [That was before contests and latest product reviews consumed so many pages of the publication.] The wait to build the rig was that I was put off by the use of an analog VFO with its attendant drift and finicky tuning. By 1999 I had learned to use the VFO stabilizers and thus the time seemed right.
From a nostalgia standpoint the VFO, built inside a 1/4 inch plate aluminum box was originally used with my 1970's LM-373 transceiver that was rebuilt in 2017. I just can't seem to throw stuff away!
This build was large and had many circuit boards. A second identical unit was built and has a much smaller footprint. Recently I have taken to stealing parts from the 2nd rig but now I think I will rebuild that rig with a Si5351 versus the analog VFO with the VFO stabilizer. Yes you guessed it the very 1st thing I liberated for the uBitx project was the cool blue display.
This series of blog posts has convinced me that I have OCD about building transceivers and should entertain professional therapy. ... Just one more rig ...