A little while ago, I got a hankering to work on a SSB transceiver. It’s something that I’ve never homebrewed before, and it seemed it like it might be fun to tackle. The BITX20 seemed like an obvious choice, and W7ZOI recently published an improved bidirectional amp which would be nice to try in the rig. But I’m one who likes to try stuff that’s a bit off the beaten path, so I decided to try my hand at something a bit different.
VU2PEP has a lesser-known SSB design on his website, that’s a dual-band transceiver. Besides having 20 and 40 meter capability, it also has a different topology than the BITX series. Instead of reversing the flow of the signal to generate a SSB signal, this design sends the RX and TX signal in the same direction through the IF. Take a look at the schematics to get an idea of what I’m talking about.
I decided to make a “remix” of this design. The basic topology is the same, but most of the circuits are revised. The IF was moved to 4.9152 MHz, and the VFO is heterodyne-style to provide a ~19.12 MHz LO signal. My version is only for 20 meters. The front end has a preamp added and uses a cascode JFET mixer instead of a single JFET. So far, the RX strip and VFO is complete (although I might change the VFO because of some birdie problems), but the transmit amplifiers haven’t been built yet. I got a good chance to work out the RX during Sweepstakes. Check out my YouTube video below to hear me describe the circuit so far and listen to the receiver on SS.
Although there are many days when I can barely stand the level of rudeness on QRP-L (and increasingly on qrp-l.org), I am sometimes reminded why I maintain my membership. Some recent events there have helped to boost up the numerator in the signal/noise ratio, and correspondingly, my interest.
In case you haven’t followed much of what has happened on the list in the last few years or haven’t listened to SolderSmoke, there’s a fellow by the name of Michael Rainey AA1TJ, who could be considered the mad genius of the QRP world. He has created what has to be considered some of the most unique and inventive minimalist QRP circuits that our hobby has ever seen. Take a look at his website to get an idea of what I’m talking about. I’ve also attached a YouTube video below showing you how AA1TJ has to operate this very unique transmitter.
AA1TJ trying for transatlantic QSO
His latest flight of fancy is his New England Code Talker voice powered CW transmitter. Yes, you heard correctly; the transmitter is powered 100% by voice sound pressure energy (about 15 mW RF output). AA1TJ has already made numerous successful QSOs with the transmitter, proving that the concept actually works. Recently he, AA1MY and W1PID met at the beach front cottage of W1REX to attempt the world’s first voice powered transatlantic QSO, as well as what was claimed to be the world’s first transatlantic QRP QSO on 160 meters (I think I misunderstood that. It’s supposed to be AA1MY’s first 160 meter transatlantic QRP QSO), both very amazing feats. I won’t spoil the story, so get yourself over to W1PID’s website to read the details of how this expedition turned out. I must salute all of you gentlemen for pushing the boundaries of our wonderful hobby and trying something never done before. Well done!
Update: Here’s the “Rexpedition2009” report about the event from W1REX (PDF format).
Update 2: A great video from W1REX showing the transatlantic 160 meter QRP QSO:
You've arrived at the blog of Jason Milldrum, NT7S. It's mostly related to amateur radio (especially homebrewing and QRP) but occasionally other topics will pop up when they strike me as amusing. The QTH is Beaverton, Oregon. I'm married to a wonderful woman who tolerates my "mad scientist" ham shack. Dad to a spoiled rotten Yellow Lab by the name of Baxter.
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