Re: [Amps] Parasitic Suppressor 4-1000A

[R@contesting.com;Measures <r@somis.org>]

On Mar 10, 2006, at 1:19 PM, Steve Thompson wrote:

> R; Measures wrote:
>
> > If a VHF suppressor does not get hellishly hot at 29MHz, it is 
> > unlikely
> > to absorb energy above 30MHz .
>
> Depending on how much energy and at what frequency, it might not need 
> to
> get that hot at 29MHz. If you can't make the measurements, then it's
> better to play safe - but that can be an open door for folk lore and
> misunderstandings.

Measuring the temperature of a suppressor R is simple with an IR 
thermometer. however, DC tests with the 100Ω, 3W @ 70ºC Matsushita MOF 
film resistors we use in our VHF parasitic suppressors,showed that they 
can withstand being operated at a dull red color in a darkened room for 
1-hour without failing.  In free air at 22ºC, 12W causes them to reach 
this temp.  During such a test, the marking ink evaporates, the blue 
dye in the ceramic coating fades to light blue, and the resistance 
decreases c. 10%.
end

> > >    Adding L increases dissipation at 29MHz,
> > >
> > > > decreases the parallel-equivalent resistance seen by the anode at 
> > > > its
> > >
> > >
> > > ..increases.. I think.
> >
> >
> > Z-meter tests show that more L-supp means less VHF RL at the anode, 
> > and
> > that means less VHF gain at the anode's self-resonant freq. --
> If the tune-C is disconnected from the plate, does the tube oscillate?
>
> Steve
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Rich Measures, 805.386.3734, AG6K, www.somis.org

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