Rick and All,
I have a Ameritron AL0811A with three 572B tubes. The power output
is about the same with the 572Bs as with the 811As on SSB or CW
because the power output is limited by the power supply voltage and
current. However, the 572Bs have much more plate dissipation than
the 811As, so I can safely run 400 or 500 watts output using PSK31 or
RTTY, a practice that would overheat and warp the plates of the
811As. When I acquired the Al-811A amp, it needed new tubes anyway,
so I just bought 572Bs, and did not change the amp in any way.
Chas W1CG
At 12:06 AM 11/7/2007, Rick Denney wrote:
Ken Brown writes...
> Last time I had an amplifier using anything like 811A tubes, they
> were actually 572B, and it took two of them to get 650 to 800 watts
> out. It was a Heath SB-200. Is that really an 811A?
I was talking about the Ameritron AL-811a amplifier, which uses three
811a transmitting tubes, not the tube itself. The 572b tubes are
indeed capable of greater output because of their higher plate
dissipation rating, their greater grid current rating, and their
higher plate voltage. Yes, the 572b is "like" an 811a tube, and some
use them in amps designed for 811a tubes because of their perceived
greater durability, but they aren't really the same.
Rick, KR9D
---
Richard W. Denney, Jr. PE|Iteris, Inc.
Associate Vice President |107 Carpenter Dr. Ste 230 | 703.925.3819
rwd@iteris.com |Sterling, VA 20164 |Fax 703.471.1757
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