Hello Cathy,
The answer is increased "RESTING" plate current in high voltage position.
Resting plate current does NOT produce any RF, so it becomes 100% heat and
0% RF. The plates dissipate extra power thus become hotter, so you have a
orange-red color.
73, Bruce, W8HW
=======================
-----Original Message-----
From: Catherine James
Sent: Saturday, January 07, 2017 12:01
To: Amps Group
Subject: [Amps] Glow, gettering, and voltage
I've noticed an interesting effect with the 3-500Z tubes in my SB-220.
When I run a kilowatt SSB on the low voltage setting on low HF bands, there
is very little glow. When I run the same power on the high voltage setting
(using less exciter drive), there is a noticeable dull orange glow.
I cannot think of a reason why higher voltage operation would be less
efficient. Thoughts?
73,
Cathy
N5WVR
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