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
