That amplifier should only be about 50% efficient so for starters your
current should be about doubled.
A bipolar transistor will only have .6 to .8 volts on the base. Check the
temperature of each device after transmitting to see if they are all pulling
their weight. Sounds like the drive is ok since both stages are drawing 10
amps. Check data sheet for resting collector current to make sure you are
not stuck in class c.
-----Original Message-----
From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
Behalf Of Ron Spencer
Sent: Wednesday, November 23, 2005 7:30 AM
To: amps@contesting.com
Subject: [Amps] MRF448 amp
Thought I would throw this out to the group and see if anyone can offer up
some help.
The amp I am working on is an old Transworld amp (the RA-1000). No schematic
is available. Just installed 4 new MRF448 (2 matched pairs).
The amp uses 2 boards with 2 devices per board.
Power supply voltage is 40V dc
When I test it I can only get max 200W out (should be good for 800 or more).
Amp has metering for collector current for both boards. Each shows 10A when
transmitting.
Any ideas on what I should be looking for? If I read the data sheet
correctly the bias voltage should be 4V. Am I correct?
Any help will be appreciated.
Thanks
Ron
N4XD
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