In our discussion regarding the SB-1000 all the above is irrelevant
anyway since the SB-1000 does NOT run class C. Use the specs for
class B (older data sheet) or class AB2 (newer data sheet) and you
will see the tube is fully capable of 600 watts RF output.
No, it is all relevant since the SB-1000 does not maintain 13.0 CFM
air flow in a pressurized cooling system. The SB-1000 is cooled by
an axial fan. Since there is no way to determine the actual air
flow in the SB-1000 cooling system, unless you can measure the base
base (200 C max) and plate (225 C max) seal temperatures under heavy
RTTY operation, it is only prudent to derate the tube to constant
carrier conditions.
73,
... Joe, W4TV
On 9/25/2012 3:11 PM, Bill, W6WRT wrote:
ORIGINAL MESSAGE:
On Tue, 25 Sep 2012 11:31:02 -0400, W4TV wrote:
Plate current is plate current, plate dissipation is plate dissipation
no matter what the class of operation. In fact, since an amplifier is
slightly more efficient in Class C than in Class AB2, the tube should
be derated even more in class AB2 than in class C.
REPLY:
You're missing the point. It's not just the class of operation, it's also the
mode of operation. Class C plate modulation is far different from Class C CW or
RTTY operation. With Class C plate modulation the instantaneous plate current
and plate voltage swing up MUCH higher than the no-modulation condition. That's
why PLATE MODULATION ratings are so highly de-rated.
In our discussion regarding the SB-1000 all the above is irrelevant anyway since
the SB-1000 does NOT run class C. Use the specs for class B (older data sheet)
or class AB2 (newer data sheet) and you will see the tube is fully capable of
600 watts RF output.
73, Bill W6WRT
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