Hello Ted, At the risk of continuing this thread for too long, brief comment. IMHO you hit on the main culprit causing problems on 20m / 30m - the inductance of R19 and R20 as supplied.
If you like, I can go off list to discuss with you your other comments. I am not surprised that you could not find evidence of other resonances, but there are ways to expose them and they are an important part of a designer's 'toolkit'. The important thing is that your problem has been solved. 73, Geoff GM4ESD ----- Original Message ----- From: "Ted Turk" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Friday, June 24, 2005 7:17 AM Subject: Re: [Elecraft] KPA100 power on 20m/30m, update > Geoff, Don, > > As an ex sufferer of this disease, my 2p worth. > > My investigations, admittedly only with the limited kit available to me > including 20MHz scope and 2 or 3 different wattmeters, I think it was, > showed that the output across all the bands up to 21MHz was remarkably > constant for a given Q1,2 base voltage (and attempt at current > calculation). However, there was a very marked voltage (estimated > current) loss across the base drive circuits on the affected bands > (C80,81/R19,20). Readings prior to this in the RF line merely > confirmed the high drive requirement as did the Hi Cur on 20/30m. With > much help and advice from guys at my club, we too considered the > possibility of other spurious resonant circuits but could find no > evidence for these in my kit at a level that affected performance. > > 73, > Ted G7BQM K2#4732 and first year RF engineering student! > _______________________________________________ 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
