Even though one of their Coronal Mass Ejections is due to hit us soon, the radio gods have been quite kind to me this morning. I installed the JBOT amplifier board in the 17 meter SSB transmitter that I had built out in the Azores during the last solar cycle. The board went in without any trouble. And I was a very surprised when it DIDN'T break into oscillation and instability! Holy Cow! This one was stable from the start! Even when connected to my antenna! Eureka!
The rig still needs some peaking and tweaking. I'm only getting about 2-3 watts out and I should be getting 4-5. I did a quick and dirty "by ear" alignment --- I just listened to my own signal with my trusty Drake 2-B and moved the carrier oscillator freq around a bit until the SSB audio sounded good (you never have to do that with DSB!).
For those of you not familiar with this rig, here is some background:
-- Built on the chassis of an old Heath DX-40
-- Crystal filter at 5.174 MHz. Filter rocks and carrier oscillator rocks from an old Swan 240 I picked up in the Dominican Republic from Pericles Perdomo HI8P (SK).
-- Based on a design published in SPRAT by Frank Lee, G3YCC (SK).
--Heterodyne oscillator is a G3RJV Universal VXO circuit running at around 23.3 MHz.
-- That orange cord to the big meter that you are no doubt wondering about is just a little circuit that monitors total current drawn by the rig. It bounces up and down as I talk. I put it in there mostly because I wanted to make use of a beautiful old Simpson meter that I picked up in 1973 at the Crystal Radio Club (W2DMC) in Valley Cottage, New York. 
Going around, clockwise from below the meter: G3RJV VXO, carrier oscillator and two diode balanced modulator board, crystal filter (with NE602 mixer and post-filter bandpass filter to the left), JBOT PA. Audio amp (using op amp) below the chassis. T/R relay in the center (antenna changeover relay below the chassis). Our book: "SolderSmoke -- Global Adventures in Wireless Electronics"
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Steve Smith sent me a good article on broadband transformers. Reading through it, it occurred to me that perhaps using a heavier gauge wire in that PA output transformer might help. So I rebuilt the FT-50-43 transformer and put it in the final. No joy -- output was still down around 1 watt. Then I tried adding two turns to the secondary (on his web page Farhan advises experimenting with the turns ratio in an effort to improve output). Again, no joy. So I went back to the FT-37-43 transformer with 12 turns on the secondary. This yields the best results so far: about 2.5 watts. Still a bit low, but for some reason, the smaller cores seem to do better. Toroidal transformer tweaking to continue... Stay tuned.
I continue to tweak and peak the JBOT amplifier in the Azores 17 SSB transmitter. On this version I used some FT-50-43 toroidal cores instead of the smaller FT-37-43 cores recommended by Farhan. This morning I was experimenting with the output transformer. I seem to get noticeably more output with a transformer made with four FT-37-43 cores than I do with one made with four larger FT-50-43 cores. 
Even though one of their Coronal Mass Ejections is due to hit us soon, the radio gods have been quite kind to me this morning. I installed the JBOT amplifier board in the 17 meter SSB transmitter that I had built out in the Azores during the last solar cycle. The board went in without any trouble. And I was a very surprised when it DIDN'T break into oscillation and instability! Holy Cow! This one was stable from the start! Even when connected to my antenna! Eureka! 
Going around, clockwise from below the meter: G3RJV VXO, carrier oscillator and two diode balanced modulator board, crystal filter (with NE602 mixer and post-filter bandpass filter to the left), JBOT PA. Audio amp (using op amp) below the chassis. T/R relay in the center (antenna changeover relay below the chassis). 
Steve Smith of SolderSmoke's West Coast bureau sent us the link to this article about a very interesting guy who made enormous contributions to the radio art. Three cheers for Norman Krim!
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