Posted by
Geoffrey Mackenzie-Kennedy on
Nov 28, 2008; 7:16pm
URL: http://elecraft.85.s1.nabble.com/Questions-about-ARRL-review-tp1583996p1590263.html
Ignacy wrote:
> If there is a problem with those capacitors at 30dbm, I am wondering about
> the power amps especially SS where ceramic caps are used extensively.
> Seems
> nearly all amp's IMD cam generated in those caps. Am I missing something?
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I suspect that when used in power amps any IMD products produced by ceramic
capacitors will be masked by the IMD products generated by the active
devices, be they tube or solid state. In a receiver the difference between
the level of a given IMD product generated by an active device and the level
of one of the 'parent' signals involved is much greater than it is in the
majority if not all power amps, which means that any IMD contributed by
passive devices can in some cases affect performance.
It is the NPO disc ceramics that I have found to be troublesome when used in
crystal filters and / or RF tuned circuits. Instead I use AVX's AQ12
multilayer ceramic chip (SMD) capacitors which are rated for use at
microwave.
Jack, I look forward to seeing your RF data.
73,
Geoff
GM4ESD
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