[Amps] caps across rectifier diodes

[Vic K2VCO]

Doug Renwick wrote:
> Sorry? ... on the contrary.
> I believe the answer from the archives is "capacitors prevent RF from
> being rectified in the diodes, and generating harmonics."

Here's the complete explanation in that thread from W8JI, who designed the AL80A and the 
SB-1000 (which I have and which has capacitors across 1N5408's):

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"1.) The diode is a non-linear component with different recovery times. Let's picture one 
diode in the string having much faster recovery time. This goes hand in hand with that 
diode having less voltage breakdown. Slowing the rise time of voltage across that diode 
(by having the capacitors reactance be much less than the diodes impedance near breakdown) 
prevents one FASTER diode from taking a big hit in voltage cycle after cycle.

2.) When the diodes do switch, the waveform is not a sine wave. Being non-sinusoidal means 
the waveform contains harmonics. These harmonics can be heard in receivers, and most ham 
stations have receivers. Even if the PA does not have to pass CE tests for powerline 
conducted EMI, why risk generating trash that can affect the receiver?

3.) Bypassing is almost always often less than perfect in high power PA's. Capacitors 
prevent RF from being rectified in the diodes, and generating harmonics."
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-- 
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco