[Amps] Low Pass Filter capacitor ratings for 1.5kw level

[Tom W8JI]

> Using a filter after the transceiver is a good idea along 
> with the one behind the amp.

In the 50's and 60's or earlier that might have been good 
advice. Not any longer though.

Anyone who has ever looked at a modern Ham radio (i.e. a 
real amateur transceiver like a Y K I) on a spectrum 
analyzer is already aware they are typically down well over 
50dB on harmonics, so any post transceiver filter is a waste 
of parts. TVI worries from exciters went away along with 
vacuum tubes. Exciter harmonic problems are now almost 
non-existent

IF ingress into TV sets is now a non-issue, rendering the 
old thought of IF frequency notching at the transmitter 
useless.

As a matter of fact in most situations amps that meet FCC TA 
requirements will even find a post amplifier lowpass 
useless.  Virtually all TVI is now fundamental overload, at 
least with amateur amps that pass TA. Cases that still exist 
center around direct off-air fringe reception, and the low 
pass requirements are much different than they were 20 or 30 
years ago.

It's a different world. The output filter has now largely 
been relegated to the uses most people here talk about, 
preventing radio-to-radio interference in multiple radio 
environments like contests. In the rare cases where one is 
needed, a stop frequency of 54 MHz and modest attenuation of 
20-50dB is enough.

73 Tom