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 > -----Original Message----- > > The "Trap theory" makes a lot of sense, and Don's comment about low > tolerance C80 and C81 capacitors would seem to support it. But if the > resistors in parallel with C80 and C81 are the only "Inductors" that form > the L part of the traps, I would have thought that by simply changing R19 > and R20 to so called Non Inductive types would cure the 30/20 > meter problem. > But this might just move the problem to a higher band because of the > inductance of leads AND PCB traces between C80/R19 and between > C81/R20. But > are these the only "traps"? Consider the low Q notch C80/R34 and C81/R35. > > -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.323 / Virus Database: 267.7.11/26 - Release Date: 6/22/2005 _______________________________________________ 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
