Sigtronics US-DR - Manual (Page 10)

d) For US-45D or US-67D units, make sure that RADIO
1/RADIO 2 switch is set to the radio you want to hear.
2. Can’t talk to dispatch (transmit) on radio through the
headset:
a) Check the connections between UltraSound unit and
the radio. Both white wires (PTT HI and LO) and the
Brown and Black wires (MIC HI and LO).
b) Check the UltraSound Radio Mic Transmit Gain adjust-
ment.
c) For US-45D or US-67D units, make sure the RADIO
1/RADIO 2 switch is set to the radio you want to trans-
mit on.
VEHICLE ENGINE ON:
1. Electrical noise (alternator whine) in headsets when receiv-
ing on radio, or ... Dispatch reports that they hear electrical
noise (alternator whine) when transmitting from vehicle
through the headsets.
a) First make sure that the problem is only related to the
radio hook up. Make sure that you did the “Electrical
Noise Test” for the intercom (without the radios con-
nected) on page 7 and fixed any problems there before
you go further. If OK then:
b) Check all six radio interface wires between the
UltraSound unit and the radio — MIC HI, MIC LO, PTT
HI, PTT LO, SPEAKER HI, and LO. Make sure that you have
the correct pin numbers for the radio you are hooking
to. Make sure that MIC LO and SPEAKER LO are not physi-
cally tied to the same pin on the radio; even if they are
tied together inside the radio.
c) If the wiring is OK, then noise is coming from radio:
i) Possible bad radio wiring, (Check radio power and
ground connections for loose or corroded connec-
tions) or. . .
ii) Excessive noise is generated directly by the vehi-
cle’s electrical / charging system - most commonly
known as alternator whine. This is only present when
the vehicle’s engine is running and recognized by the
fact that the pitch or frequency of the whine changes
directly with the change in engine rpm.
The preferred way to solve this type of problem is to
have the vehicle’s electrical / charging system ser-
viced. The most common cause of this type of noise
is bad diodes in the vehicles alternator. Other pos-
sible causes are: Bad vehicle voltage regulator; Bad
alternator or battery cable connections; Missing or
bad engine or alternator grounding straps.
If servicing the vehicle’s charging system is imprac-
tical, installing a good alternator whine power line
filter in-line with the radio power wire(s) will usually
accomplish the same thing. All radio power wires
will have to be filtered. Some radios have more than
one wire that hooks to vehicle power. Contact the
radio manufacturer for a recommendation on the
best filter for the particular radio. NOTE: This solution
should not be considered a permanent fix. Vehicle
charging system problems of this type will eventually
cause other equipment failure as well as shorten the
life of the vehicle’s batteries.
2. Dispatch says too much background noise or unclear or
weak transmissions.
a) Check to see if a radio hand mic on the vehicle is
also active or “live” when transmitting through the
UltraSound unit. Check this while not wearing a head-
set and by talking directly into the radio hand mic and
pressing either UltraSound PTT switches. Do not press
the PTT button on the hand mic itself. If dispatch can
hear you loud and clear, then the background noise
pick up is coming from this active hand mic. If you have
this type of hand mic, then it is best to contact the radio
manufacturer for instructions on a possible microphone
modification to fix the problem. Some radio manufac-
turers can supply a compatible microphone that does
not have this problem.
b) Adjust the UltraSound Radio Mic Transmit Gain con-
trols. If the mic level is set too low, you will get reports
of weak transmissions. If the mic level is too high, you
will get reports of noisy or garbled transmissions. See
“Radio Mic Transmit Gain Adjustment” on page 9.
Radio 2 Hook Up:
Plug in J3 of the Radio 2 Interface Cable into P3 of the
UltraSound unit. Using the radio manual and Figure 5 on
page 6, connect the six wires to the appropriate connections
on the vehicle’s radio. Once that is done you will need to set
the RADIO 2 VOLUME switch on the back of the UltraSound
unit. See Figure 6 on page 9. For most applications use the
default setting of “LO” (down - which is the reverse of the
Radio 1 switch). If the vehicles radio volume has to be turned
up too high to hear it in the headsets, set this switch to the
“HI” position.
Next, set the Radio 2 Microphone Transmit Gain. The Radio
2 Microphone Transmit Gain Adjustments are the top set
of the two located on the back of the UltraSound unit. The
adjustment procedure is very similar to that of the Radio
1 Mic Transmit Gain adjustment. First set the RADIO 2 MIC
XMIT GAIN RANGE switch to the “LO” position (default set-
ting). NOTE: the HI and LO switch positions for Radio 2 are
upside-down from that of Radio 1. Arrange to have someone
nearby with a radio compatible with your Radio 2. Then, pro-
ceed as follows:
1. Again, plug in a headset into Officer’s jack. Make sure that
the volume control on the headset is turned up to full.
(Radio 1 and the other headsets are not needed for this
adjustment.) Set the RADIO 1/RADIO 2 switch to “RADIO
2” and the AUTO/BOTH switch to “AUTO”.
2. Put on the Officer’s headset and position the headset
microphone as normal. Turn the UltraSound VOLUME
control all the way down (counter-clockwise). You should
not be able to hear yourself in the headset.
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