So K2 Gentelmans...one question.. To fix RF switching problem in KPA100 there are 3 way's available (posted)
1. 12pF to ground from 1n4007's junction (just mooves a problem arround) 2. 1K resistor instead of RFC3 (affects RX preformance and marginal switching at high power levels) 3. Change RFC3 100uH with 1mH choke (dont know abt side effects but shure want to know the current rating of choke, cause i suppose must be at least 150mA or more?) Which way is the best for now? All kind of Help is Wellcome! Thanks in advance! S55M-Adi K2-3204 ----- Original Message ----- From: "Stewart Baker" <[EMAIL PROTECTED]> To: "Don" <[EMAIL PROTECTED]>; "Elecraft Reflector" <elecraft@mailman.qth.net> Sent: Wednesday, December 29, 2004 7:29 PM Subject: Re: [Elecraft] KPA100 - 80m poor quality SSB >>> 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: Elecraft@mailman.qth.net 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 _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
