Yaesu FT-901DM Maintenance Service Manual page 82

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IF unit (PB-1704)
2. VOX ADJUSTMENT
Tune in a signal and adjust the AF GAIN control
for a normal listening level. With the microphone
positioned near the speaker, increase the VOX
GAIN control on the front panel until the speaker
output causes the VOX relay to switch to the
transmit mode. Set the ANTITRIP control VR¢o;
on PB-1685 to the point that will just prevent the
speaker output from tripping the VOX relay.
Speak into the microphone in a normal voice to
see if one's voice will activate the VOX relay. If
not, VR¢o; may be advanced too far.
Adjust the DELAY control VR¢o2 for the desired
release delay. Clockwise rotation of VR¢o2 will
increase the delay time. For CW semi-break-in
operation, VR6go2 should likewise be adjusted to
suit the operator's preferences. For CW operation
with a footswitch for relay actuation, the VOX
GAIN control may be rotated fully counter-
clockwise (but not to the click-stop, which is the
MOX position) to disable the VOX system.
3. CW SIDETONE LEVEL
Adjustment of the CW sidetone level may be may
"be made by adjustment of potentiometer VR¢o3.
located on PB-1685, while the transceiver is being
keyed.
4. CARRIER BALANCE
The transceiver should be allowed to reach normal
operating temperature before making carrier
balance adjustments.
SERVICING
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VOX/Marker unit PB-1846 (PB-1685-3330)
Tune up the transceiver for SSB operation using a
matched antenna or dummy load. Turn the MIC
GAIN control fully counterclockwise to remove
all audio input from the modulator stage.
A more precise balance may be obtained by tuning
a receiver which has an S meter to the transmitted
frequency. Adjust VR7o, and TCy9s for a mini-
mum S meter reading on the remote receiver
while switching the MODE switch back and forth
between the two SSB positions: this will help
ensure good carrier suppression on both LSB and
USB
TCr7 TEr03 TC:
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Carrier unit (PB-1706)