>>> Although the 1k resistor mod seems to work there is a noticeable drop in >>> received signals. >>> Modeling the KPA100 T/R switching showed this additional loss. >>> As a temporary measure until the official Elecraft modification comes out >>> I have replaced RFC3 (100uH) with a 1mH RFC. >>> My simulations show that the circuit resonance is now around 1.2MHz- maybe >>> lower. Tried all bands, can't find a problem.
>>> 73 >>> Stewart G3RXQ On Tue, 28 Dec 2004 18:11:15 GMT, Stewart Baker wrote: > On Tue, 28 Dec 2004 09:36:00 -0800, Don wrote: > >> Stewart, >> >> I have been in contact with Gary intermittantly since first coming across >> this problem in October. He assures me that Elecraft is working on a >> solution and will have something to say soon. Both the "12 pF" fix and the >> "1000 ohm resistor" fix have proved effective but are probably not the most >> elegant or foolproof ways of solving the problem. For instance, the 1000 >> ohm resistor alters the reverse bias on D14 in a way that makes the T/R >> switch marginal at high power levels. I suspect that Elecraft is taking >> their time and checking out all of the possible effects of design changes >> and mods before committing to a final solution. >> >> We will just have to be patient. >> >> Don K7FJ >> >> >> The guests having departed - the Turkey finally disposed of - the booze >> consumed >> - thoughts turned to "Playing radio". >> >> I have been getting reports on 80m that my SSB signal had some "edge" to it. >> At first I put it down to RF feedback, but that was not the problem. >> >> I used my FT1000MP to listen to the 2nd harmonic of the 80m signal. >> Having read recent mails I first monitored the 3.5MHz signal and found the >> "Buzz" that others had reported. >> >> I then tried the following frequencies on 80 and noticed that as I increased >> the >> power control on the K2 the power output would suddenly jump, then when the >> control was turned ACW the power would reduce smoothly and then suddenly >> drop. >> It was also observable on the FT1000MP S-meter, accompanied by a click. >> It was like a form of hysteresis. All other bands gave smooth power control. >> >> The results were as follows:- >> >> 3.8MHz Low point=20W High point=70W Hysteresis=50W >> 3.7MHz Low point=25W High point=70W Hysteresis=45W >> 3.6MHz Low point=35W High point=70W Hysteresis=35W >> 3.5MHz Low point=40W High point=70W Hysteresis=30W >> >> Very unsatisfactory... >> >> I substituted a 1k resistor for RFC3, and all the 80m problems went away. >> Smooth power control on all bands and a better SSB signal on 80m. >> >> Many thanks to those who found/cured this problem that first showed itself >> on >> CW, I would certainly have spent a lot of time tracking this one down ! >> >> I would suggest that owners of K2/100's check to see that their rig does not >> exhibit these symptoms as it can make quite a big difference to transmitted >> signal quality. >> >> I, like a previous correspondent think that Elecraft should make some >> comment on >> this design problem, and it's solution. >> >> 73 >> Stewart G3RXQ >> > Thanks for the "Heads up" Don. > I will look forward to the official modification when it is released. > > 73 > Stewart G3RXQ _______________________________________________ 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
