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After tuning has been completed for best power output and
efficiency,
screen control R405 should be set for the desired
power output.
In no case should the output circuit be de-
coupled to reduce output power.
It should be emphasi,ed that this amplifier is easily over-
driven.
For 50 watts output power approximately
3
watts
drive is require;.
For 15 to 25 watts output power,
about
1 watt of driving power is required.
If driving power is
increased above the required amount, power output of the
amplifier will fall off due to high grid leak bias being
created.
A typical set of reading are given on this amp-
lifier on the following page.
Coupling Amplifier To Another Stage.
-
dhen the amplifier is going to be used to drive another amp-
lifier stage,
it is suggested that it first be tuned up into
a load and then coupled to the grid circuit of the following
amplifier stage.
To reduce the possibility of oscillations and/or parasitics,
the input circuit of the following stage should be properly
coupled and matched to the 51 ohm coaxial line connected to
the output of the 50 watt amplifier.
This may be done with
a micromatch coupling unit.
The following grid and input
circuit should be adjusted for minimum SWR.
If a micromatch coupling unit is not available,
the input
coupling and grid tuning of the following stage should be
tuned for maximum grid current in that stage.
If the following input circuit is properly matched, plate
tuning of the 50 watt amplifier will not change appreciably
when switching from a non- reactive load to being coupled to
the following amplifier stage.
If the 50 watt amplifier stage was properly tuned up into a
load and plate tuning deviates radically from where it was
after being coupled into another stage,
a major mis - match
exists.
If the 50 watt amplifier unit is over- driving the following
amplifier,
screen control R405 should be adjusted for the
desired drive.
Do not de- couple the 50 watt amplifier stage.
6/25/58
-2-
m5675
Amp.
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