AM develops PEP of 4 times the carrier power at 100% modulation. This is
your 375 - 1500 PEP relationship.
Your "flat topping" is not caused by the AMP running B or AB and
overmodulating, it would be caused by the inability to handle the PEAK POWER
you are trying to get it to handle.
You need to build the amp to handle the relationship. If you wanted to run
a PEP Output of 2500 watts it needs to be able to handle that output. The
input carrier would be 625 watts.
In your situation however my guess is the amplifier is not your problem but
your exciter. (As I assume you haven't modified your AL-1200 for plate
modulation.) You are clipping in the exciter when trying to drive your amp
to higher power.
IN the form of RF service you are operating Linear amplifying a modulated AM
signal B or AB or even A would not improve your situation.
In Class A to answer your question, you would need to dissipate every bit of
the PEP power level you are looking to put out in resting condition.
I'm surprised more AM operators haven't built modulators to add to things
like AL-1200's etc and plate modulate them.
You would sound a whole lot better than Keying up your FT-101 and sending
that AM to the AL-1200 in linear mode.
BOB DD
-----Original Message-----
From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
Behalf Of kenw2dtc
Sent: Wednesday, November 08, 2006 12:41 PM
To: amps@contesting.com
Subject: [Amps] class "A" RF amp question
If one were to build a class "A" RF tube amplifier capable of producing an
AM signal of 375 watts carrier and 1500 watts PEP, what would be the plate
dissipation required by the tube? (I know how stupid and inefficient this
is, but I really would like an answer).
As background, I have an AL-1200 (3CX1200A7) which starts to flattop beyond
375 watts of carrier at 100% modulation and this amp is class "AB2", so I
know class "A" would require significantly more dissipation than 1200 watts.
73,
Ken W2DTC
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