hi Don, I have been quite successful yesterday thanks to your suggestions. The major advance was grounding the microphone shell. I did it from the left side with a piece of desoldering braid and a lot of heat. This cured most of the distortion in my signal and all of the wiggle of the microphone shell I had noticed before.
Next step was modification of the SSB board. I had no 15k resistor at hand but one at 5k so I put it in series with the existing 10k resistor, the resistor between Q1 and pin 6 of P1 is mounted "elevated style" with one lead very short at P1 the body 60° up and a longer lead to Q1 going down again. (I had no 1/8 W resistor.) The last part was the power supply. I had a clear signal on 80m but my buddies reported some clipping on 20m and 10m at high power. I had attached the low power cable to the main 12V supply of my station, and the high power supply to a different 20A PS. This turned out to cause the problem - probably a ground loop with the antenna system. When I connected both 12V lines into the 20A power supply I had a good signal on all bands (at least it sounds good in my monitoring receiver) Test on air will follow, but I think everything is working now. Thanks a lot, 73! de Werner OE9FWV On 27 Nov 2007 at 11:13, Don Wilhelm wrote: > That link pointed me to a page that includes the KI6WX Increased Gain > Mod as well as a few other changes to the KSB2 board (increased > compression, etc.). > > The Increased Gain Mod alone may be your problem. If you are to use > that with the KPA100, make the following additional changes to the > KSB2 board: 1) Increase the value of R9 to 15k 2) Cut the trace (on > the top of the board) between P1 pin 6 and the base of Q1. 3) Add a 1k > resistor between P1 pin 6 and the base of Q1 - note that this is a > tight squeeze for a 1/4 watt resistor, but it does fit - you may also > use a 1/8 watt resistor or an SMD resistor if you have one available. > > Make the above changes and then test again - it may correct all your > problem. > > The Increased Gain Mod will not show this problem at QRP. It only > shows up when the gain of the KPA100 is added to the RF transmit > chain. > > Grounding the shell of the Microphone connector is on the K2 front > panel. It can be accomplished without disassembling the front panel. > Remove the left side panel and you can access the side of the > microphone jack. Scrape a bit of the solder mask material from an > area near the mic jack to expose some of the copper (and tin that > area). Solder a short wire onto the shell of the mic jack (this takes > a lot of heat, so use a larger iron or a high heat setting) and also > onto the copper ground plane of the front panel. It is a little > easier if you disassemble the front panel board from its metal > housing, so you may take your choice of how to proceed. -- "Outside of a dog, a man's best friend is a book. Inside of a dog it is too dark to read." Groucho Marx PGP-Key: <http://www.qsl.net/oe9fwv/furlan.asc> Fone +43 5522 75013 Fax +43 820 555 85 2621 Mobile +43 664 6340014 _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
