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

[Fuqua, Bill L]

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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