[Today’s run: run/walk 4 miles in the afternoon]
I think it was in 2001. I had gotten interested again in ham radio shortly before 2000 and by 2001 I was back on HF with a 40 meter QRP radio.
I was on some email mailing lists about QRP (low power) radio topics. Someone put together a group project. People who wanted to participate could buy the Small Wonder Labs SW-20 QRP transceiver and be lead through the construction step by step.
I decided to give that a try. I really learned quite a bit. The SW-20 is based on the NE-602 mixer/amplifier chip. It is CW only, its varactor tuning covers about 50 kHz of the 20 meter band, and has a nice IF crystal filter in it. The power output is around 2 watts. It has NE-602 chips in the front end and as the product detector.
I got mine built ok. The enclosure I bought was a bit tight. I ended up grinding down the sides of the board just a bit to allow it to fit. Small Wonder sold an add-on kit called a Freq-Mite which tells you your working frequency in the headphones using morse code. I bought that too.
Anyway, I was using my other 20 meter qrp rig the other day (the Willamette, another group project) and decided to give the old SW-20 a comparison run. It wasn’t working well at all. I discovered that the antenna jack had become disconnected on the ground side. After I fixed that I touched up the alignment and used it to talk to a guy in Ohio.
As for comparison, the SW-20 is a single-signal superhet and that crystal filter makes quite a difference in listening performance. I think the direct conversion Willamette is a bit more sensitive and a purer signal. An interesting feature of the SW-20 is that the side-tone is generated by leakage from the transmitter. I thought that was a neat idea. The Willamette has RIT (which can be added to the SW-20). I personally enjoy the direct-conversion-with-RIT operating experience more then the superhets. A classic example of what I’m talking about is the TenTec Century 21.
There is a modification I could do to expand the frequency coverage. I am thinking about that and about maybe putting it in a different enclosure.
I have my old SX-11 and GPSDO projects still in play, so maybe the SW-20 improvements will happen later down the line.
(I would really like to get another 40 meter qrp rig and something that will operate on 30 meters.)