[Boatanchors] 812 vs 811 Transmitting Tubes

[Sandy]

No, No, No....definitely NO!

The 812A and 811A appear to be identical, but the amplification factor is 
greatly different!

The 811A will work at or near zero grid bias.  To plug in an 812A will 
invite disaster!

The 811A was originally designed for Class B operation.  Usually Push-pull 
in audio and single tube or multiple parallel tubes in RF Amplifier Class B 
or AB operation.

The 811A was designed for RF amplifiers in Class C operation.

The 811A CAN be operated in Class C operation for slightly higher 
efficiency, but then is only good for CW or plate modulated AM telephony 
modes, not SSB which is the predominant "voice" mode today.

73,

Sandy W5TVW
----- 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: [Boatanchors] 812 vs 811 Transmitting Tubes


> Looking at the data sheets, the 811 and 812 look to be nearly identical.
>
> 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
>
> -- 
> ***********************************************************
> Dave  N7RK          Boatanchors Home Page: http://members.cox.net/n7rk
> Phoenix, Arizona         *DXCC Honor Roll*    *WAZ#22 - 75 Meter SSB*
>
> ex-XE2/N7RK, N7RK/ZB2, VK2ERK, ZM0AJN, WB6NRK, WN6IWX
>
> Boatanchor and Antique Radio Collector
>
> _______________________________________________


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