Gary -
In a word.... NO.
The PA stage is operated as a LINEAR amplifier, Class AB1, meaning the output signal is a reasonable
facsimile of the input signal. The BIAS voltage is carefully chosen to 'center' the operation of
the amplifier in the linear portion of the tube's operating region.
Increasing the BIAS voltage WILL reduce the IDLE current, (between code elements,) but will shift
the PA to a non-linear region. This will result in distortion of the signal, with the potential of
spurious signals, clicks, and other 'junk'. This is one reason clicks were so prevalent in the older
transmitters. A true Class C amplifier requires considerably more driving power, and relies on the
'flywheel effect' of it's output network to 'smooth' out the 'pulses' of drive that exceed the bias
potential.
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs
<www.k4oah.com>
Gary Winblad wrote:
All this talk of rebuilding AC-4 supplies had me thinking...
I have seen a mod(?) that said to turn up(down?) the bias when running CW
(and FSK?) to set the finals more to Class C operation to save power
dissipation.
Is this a good idea? Wouldn't it be easy to add a switch or relay and
another potentiometer while you are in there rebuilding?
73,
Gary
WB6OGD
http://mailman.zerobeat.net/mailman/listinfo/drakelist
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