Daniels Electronics MT-3 Series, Installation And Troubleshooting Manual

Page: 8 / 9

DANIELS DANIELS
ELECTRONICS LTD. ELECTRONICS LTD.
TM TM
TN100 System Installation and Troubleshooting
MT-3 Radio Systems
3.2 Receiver Has No Squelch Tail
1. The receive and transmit repeat is very fast. To create a squelch tail the transmitter PTT uses a hang
timer to keep the transmitter keyed a moment longer after the input Tx key signal is removed. The hang
timer circuitry is located on the audio contro cardl. Ensure that the hang timer is enabled and the hang
timer adjustment potentiometer is set to an appropriate length of time. Refer to the audio control card
manual for more information on this control.
3.3 Receiver(s) are Noisy and Exhibit Poor Sensitivity
1. Check the battery charging circuits and/or the power sources to determine that the DC charging cir-
cuits are not noisy. Try removing the battery charge source, then re-test the receiver. Repair or replace
the charger if defective.
2. Examine all RF connectors thoroughly. Pull on the RF cables slightly and listen for any changes in
the receivers performance. Check that the center pin of the RF connector is correctly mounted (captive
center pin RF connectors should be used).
3. Check the duplexer alignment if the transmitter appears to de-sense the receiver module.
4. Review the installation area for any "data" or "clock" sources that may be causing harmful interfer-
ence.
4.0 System Monitor
4.1 +9.5 Vdc Switching On and Off
1. Depending on the hysteresis settings in the SM-3 (factory standard is 8 Volts shut-off, 11 Volts turn-
on - see system monitor instruction manual for different settings), the hysteresis circuits can oscillate if
a battery cell fails (opens) and the subrack is in the receive mode. In the receive mode, the current drain
is low and the "open" battery may still deliver the current required by the receiver circuitry. If the trans-
mitter is activated when a receive signal is present (normal repeat), the battery may drop below the SM-
3 hysteresis cutoff point, shutting the power (+9.5 Vdc) to the other subrack modules off, and reducing
the load to the batteries. When the load is reduced, the battery voltage will increase and turn on the SM-
3 hysteresis circuit. This condition causes the subrack modules to turn on and off which will not dam-
age the radios but does indicate a serious failure in the battery system.
Operational Troubleshooting
Page 8 of 9
43 Erie Street Toll Free Canada & U.S.A. International Internet
Victoria, B.C. Phone: 1-800-664-4066 Phone: 250-382-8268 e-mail: sales@danelec.com
Canada V8V 1P8 Fax: 1-877-750-0004 Fax: 250-382-6139 web: www.danelec.com
TECHNICAL NOTES
TN100 Rev 3-0-0 Sep 08 © Copyright 2008 Daniels Electronics Ltd. All rights reserved.
TT
hh
iiss
pp
rroo
dd
uu
cc
tt
hh
aa
ss
bb
ee
ee
nn
dd
iiss
cc
oo
nn
ttii
nn
uu
ee
dd
aa
nn
dd
iiss
nn
oo
lloo
nn
gg
ee
rr
mm
aa
nn
uu
ffaa
cc
ttuu
rree
dd
bb
yy
DD
aa
nn
iiee
llss
EE
llee
cc
ttrr
oo
nn
iicc
ss
LL
ttdd
..