{Collins} 812 vs 811 Transmitting Tubes

Nigel Holmes Holmes.Nigel at ABC.NET.AU
Thu May 29 00:37:52 EDT 2008

 The 811 was intended for linear, moderately low distortion amplifiers
typically class B audio while the 812 was a parallel development
intended for non-linear rf amps.

The 811 spawned a range of spin-offs like the 572B when amateur SSB
kicked off in the 50's and it was found the 811 made an efficient rf
linear amplifier with little or no bias required.

The 812 on the other hand requires large pots full of bias...

Putting 812 in an amp designed for 811's will cause your shack to be
illuminated (briefly) by the incandescent glow of melting anodes
possibly followed by the depressing stench of incinerated transformer.
Or the fuse will blow. 

Data on both valves can be found in any ARRL handbokk 1940's onwards.

73  Nigel VK3DZ

----- Original Message -----
From: "David Hollander" <n7rk at cox.net>
To: <collins at listserve.com>; <amswap at mailman.qth.net>; "BOATANCHORS" 
<boatanchors at mailman.qth.net>; "Old Tube Radios"
<boatanchors at theporch.com>; <BOATANCHORS at LISTSERV.TEMPE.GOV>
Sent: Wednesday, May 28, 2008 10:10 AM
Subject: {Collins} 812 vs 811 Transmitting Tubes

> Looking at the data sheets, the 811 and 812 look to be nearly
> Can you replace 811's with 812's in an amp such as a 30L-1 or any 
> other amps that use 811's?
> Any comments?
> 73 es Tnx,
> Dave N7RK

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