Hello Don, Yes I understand the purpose of the RC compensation circuit in the drive path to each transistor to offset their decreasing gain as the working frequency increases, and which cannot be fully dealt with by the RCL network in the primary circuit of T1. As you say say they are not intentional traps, which is why I use the term "spurious resonant circuits". The possibility of unwanted resonances in the feedback networks eg R39, C59, R35 is very real. If for example R39 and C59 were to be a series resonant circuit at X MHz, the in-circuit gain of Q2 would decrease at X MHz.
RF design is an unforgiving mistress!! 73, Geoff GM4ESD ----- Original Message ----- From: "W3FPR - Don Wilhelm" <[EMAIL PROTECTED]> To: "Geoffrey Mackenzie-Kennedy" <[EMAIL PROTECTED]> Cc: "Elecraft Discussion List" <[email protected]> Sent: Thursday, June 23, 2005 9:58 PM Subject: RE: [Elecraft] KPA100 power on 20m/30m, update > Geoff, > > These are not intentional traps, but are a parallel RC circuit to adjust the > base drive with frequency (at low frequencies, the resistors are the main > path, at higher frequencies, the capacitors pass more RF). This is done to > compensate for the gain vs. frequency characteristics of the transistors. > The inductance of the resistors is just an unfortunate by-product (but must > be considered just the same in the design). > > 73, > Don W3FPR > _______________________________________________ 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
