1 kW TTS1000B TRANSMITTER IPA ASSEMBLY
PUB96-30 rev 1: Jul 1, 2010
30-4
1 kW IPA Assembly VHF
1.Set
up
a
50
V
power
supply,
current
limited
to
a
little
more
than
1.2
amps.
2.Turn
both
bias
potentiometers
to
their
maximum
resistance
position.
Remove
both
fuses.
3.
SRF
3943
‐
2
Intermediate
Power
Amplifier:
LB
Setup,
continued.
3.Apply
the
50
V
supply
to
one
transistor
at
a
time
(one
half
package)
and
adjust
the
corresponding
bias
resistor
for
600
mA
drain
current.
These
settings
are
a
starting
value,
which
will
be
readjusted
during
system
test,
for
minimum
intermods
and
FM
noise.
4.Connect
a
30
dB,
20
W
attenuator
to
the
output
of
the
amplifier.
This
will
absorb
amplifier
output
and
protect
the
sweep
detector.
Use
it
instead
of
the
20
dB
pad
shown
in
the
diagram
below.
5.Reinstall
fuses
and
apply
B+
to
both
supply
connections
of
the
amplifier
module.
6.Apply
a
low
level
sweep
to
the
amplifier
and
measure
the
DC
input
current
(not
more
than
1.2
amps)
and
gain.
Gain
of
the
amplifier
alone
should
be
about
20
to
24
dB,
and
with
the
preamp
(R5
at
maximum)
the
combined
gain
should
be
between
32
and
38
dB.
Flatness
over
the
band
should
be
better
than
1
dB,
as
shown
in
the
following
diagram.
Curves
for
chs
2
‐
4
and
5,6
are
correct:
