[Amps] 813's.. Parasitic suppressor's

[Carl]

What is the parasitic frequency of the 813?

Since they have good gain to at least 6M there is no reason to assume they 
are parasitic free.

Carl
KM1H


----- Original Message ----- 
From: "Fuqua, Bill L" <wlfuqu00 at uky.edu>
To: "Jim Thomson" <Jim.thom at telus.net>; <amps at contesting.com>
Sent: Monday, April 12, 2010 9:48 AM
Subject: Re: [Amps] 813's.. Parasitic suppressor's


> Many transmitters were built with out parasitic suppressors during WWII 
> using 813. I believe it is because the gain drops quickly above 30MHz and 
> there is less of an opportunity for the tube to oscillate at VHF 
> frequencies. Most glass "modern" glass power grid tubes are at least good 
> for full output up to
> 110 MHz so that they can be used in FM broadcast transmitters.
> 73
> Bill wa4lav
> ________________________________________
> From: amps-bounces at contesting.com [amps-bounces at contesting.com] On Behalf 
> Of Jim Thomson [Jim.thom at telus.net]
> Sent: Monday, April 12, 2010 6:35 AM
> To: amps at contesting.com
> Subject: [Amps] 813's.. Parasitic suppressor's
>
> Somebody asked a while back  abt the need for parasitic suppressors'  on a 
> GG- 813 amp.  A buddy
> had one blow up on his  2 x 813 amp last yr.. across  town.  he tossed 
> both the blown one.. and also
> the remaining one.  Amp runs just fine with NO suppressors.   Another 
> fellow  runs a 4 x 813  amp,
> again with no suppressors.   The tubes all balance out too..equal glow. 
> I'd try it with it with no suppressors
> 1st.... then if you do have stability problems.. then add them.
>
> If the screen and control grids are well grnded [via strap] to chassis... 
> you won't have stability problems.
> I have had  813's  with as high as 3 kv on em, no load... yrs ago, with no 
> stability problems,  but that amp
> did have suppressors in it   [2 x 813's in GG]  [80-10m].   That was back 
> in 1975.   It's  a pretty stable tube.
>
> Later... Jim   VE7RF
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