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Tac/Com Control Head Manual SM06 Rev. 4.10
2.5 Troubleshooting
2.5.1 Weak Receive/Transmit, Intermittent Operation, Erratic Squelch
Ensure all antenna mounts are secure, cleanly grounded, and well terminated. Avoid
sharp coax cable bends or crushed coax from tie wraps. Never mount any antenna on
a composite surface unless a well-grounded and adequately sized (equal in radius to
the height of the antenna) ground plane has been provided. Keep antennas widely
separated, especially between VHF radios, and VHF and UHF radios. Bad antenna
matches and close proximity will result in large amounts of spurious radiation, which
may affect VHF-FM to VHF-AM operation and may result in harmonic interference
between VHF and UHF radios.
2.5.2 Strange Noises, No Receive Audio, Transmit Keying problems
Buzzes, hums or other background audio noises are symptomatic of multiple grounds or
noisy external systems such as inverters, blowers or pumps sharing wiring with the
audio system connections. Failure to key or correctly modulate a transmitter, or no
receive audio is often caused by not connecting all required grounds or wires to the
radio or external audio system. Check to make sure that the MIC AUDIO and PTT lines
are not reversed (keys, but no TX audio). Be sure both audio output wires are
connected from the transceivers (no or very faint RX audio).
A special caution is that no audio ground should be taken from the front instrument
panel or similar location that shares a ground return with a turn and bank or horizon or
other motor driven instrument. If this caution is not observed, the sound of the t&b
motor may be heard mixed in with receiver audio.
2.5.3 Some Frequencies Can't be Edited
Some frequencies are not really agile entries (such as crystal guard frequencies), and
as such should not be edited during normal operation. All such entries must be set via
the MASTER EDIT mode (see Section 3.11).
When in the SIMPLEX mode (RX and TX frequency lines display an 's'), you cannot edit
the TRANSMIT portion of the radio channel assignments because there is actually a
valid TRANSMIT frequency stored. It is temporarily hidden because of the SIMPLEX
function. To edit these frequencies, simply return the control head to DUPLEX
operation via the STATUS EDIT function or front panel switch, as appropriate.
2.5.4 Display Brightness is Too Low, Can't Increase to Full Brightness
The intensity of the display is set by two functions, the level set from the display screen
(advance the cursor past the last radio, then set the brightness up or down with the
SELECT switch) AND the status of the panel dimmer line. If the dimmer is active, then
the display automatically dims to HALF BRIGHTNESS of the previous setting. In some
Page 2-6 Jan 4, 2006
ENG-FORM: 805-0108.DOT
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