Page 14
Possible Causes of Noisy Audio
1.
Excessive Distances
Operating at distances greater then 200 ft. may cause some intermittent
noise.
2.
Channel Selection
For operation with non-companded receivers (such as PR-75 or PR-72),
the M-175 transmitter must be set to one of 10 non-companded channels
91-00. For high-fidelity operation, the companded channels 1-88 must
be used with companded receiver PR-216/72MHz model.
(See page 9 for Frequency Information.)
3.
Gain Problem
Check the microphone gain setting on the M-175 transmitter for normal
operation with the “voice” modulation indicator (See page 2 section d.)
Low modulation will render poor signal-to-noise ratio.
4.
Channel Interference
Monitor the receiver with the headphone plugged in and with the
transmitter turned “OFF” on the channel that the transmitter is tuned to.
If interference noise is heard, a new clear channel must be selected.
5.
Transmitter Power and Receiver Sensitivity
Check the M-175 transmitter with the PR-75 or PR-216/72MHz receiver
for normal R.F. sensitivity. This can easily be done by range checking the
receiver and transmitter with the microphone cord antenna removed
from the transmitter. Tune the receiver and transmitter to a clear channel
and place the transmitter on a non-metallic table. Remove the microphone
cord antenna from the transmitter, and turn on the transmitter. Plug
the headphone cord into the receiver, and turn the receiver on. Then
walk away from the transmitter while listening for noise build-up
just before the squelch action takes place. A distance of 10 to 15 feet
should be obtained with the PR-75 or PR-72 and 20 to 30 feet with the
PR-216/72MHz receiver. If the receiver and transmitter do not pass this
test, both receiver and transmitter must be returned to COMTEK for service.
M-175 TROUBLE SHOOTING
(Continued)
