Tim Shoppa wrote:
On Aug 9, 6:46 pm, Kenneth Scharf wrote:
This link goes to the Svetlana sv811-10 which is NOT the same as the
ORIGINAL RCA 811 transmitting tube. Svetlana had no right to call this
bottle an 811 as it does NOT have the plate cap, is NOT a transmitting
tube, and has a mu of 10 not 160!
This is a nice AUDIO tube, more of a replacement for the 300B than an 811!

Actually, the 811 was sold by RCA as the "audio tube"; they sold the
similar but not identical 812 as the RF tube. The beauty of the 811 as
a push-pull class B modulator is the low parts count and you don't
need any bias supply.

It was only in the 1950's with the advent of SSB that the simplicity
and excellent characteristics of the zero bias triode became clear in
RF linear amplifier service. Before that everyone ran all their RF
stages in class C for efficiency. It was the 30L1 in 1960, and some
hams experimenting with zero bias in the 50's, that placed the 811A in
the RF tube category. RCA of course was more than happy to sell the
tubes for whatever purpose :-).

Oh, here's a 811 (non-A) datasheet from HB3:
http://www.pmillett.com/tubedata/HB-..._Tubes/811.pdf

Good reading that mentions 811 marketing, and the advent of zero bias
triodes for SSB linears, is in the 1996 QST article: "811A:
Grandfather of the zero bias revolution". It notes that the main
difference between the 811A and the non-A, was the addition of extra
fin area in the 811A to boost dissipation.

Tim.
Thanks! That's the one.
While it is true that the 811 was originally intended for use as an
audio tube in modulators RCA also published spec's on using it as an RF
final. May hams used the same tube type in both places so as to only
keep one tube type for spares. Audiophools today probably search for
812's for use in single ended class A amps.