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@uky.edu>
To: "Jim Thomson" <Jim.thom@telus.net>; <amps@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@contesting.com [amps-bounces@contesting.com] On Behalf
> Of Jim Thomson [Jim.thom@telus.net]
> Sent: Monday, April 12, 2010 6:35 AM
> To: amps@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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