Specifications

Installation
MICOM-H Owner’s Guide 61
DC Connector J4
DC connector J4 is mounted on the rear panel of the radio. It is used to feed the radio
with the required power from an AC to 13.8V power supply or from the battery. The
following table lists the function of the DC connector lines.
Reduction of
Vehicular Noise
Most vehicles are subject to several noise sources which greatly disturb a received
signal. The most noisy sources are the high voltage ignition sparks that are produced
at the vehicle's plugs. Alternator activity also generates significant noise.
By following these insulation guidelines, and if necessary by adding certain damping
components, it is usually possible to reduce vehicular noise:
1.
Keep your antenna tuner and antenna as far as possible from the engine
compartment.
2.
Connect the primary power lead of the radio directly to the battery instead of the
starter relay. The battery acts as a large capacitor (about one farad for 50 A-H
capacity batteries) by passing the noise to ground.
3.
If necessary, connect 0.01 - 0.1 mF capacitors across the primary leads of the
coil and across the alternator output.
4.
Keep your DC and RF cables as short as possible.
5.
If your vehicle does not have a resistive ignition wire, it is recommended to
replace it with such a wire.
6.
The MOTOROLA RF noise reduction kit for alternator equipped vehicles
(TLN8845) includes some useful accessories for noise reduction, including a
resistive ignition coil suppressor cable. In severe noise conditions, you may find
this kit helpful.
Table 3. Connector J4, Pin Connections
No. Pin Name Description
1
TX Power Used to deliver high currents (up to 28 Amp) to the
radio, mainly for the transmitter circuitry
2
Ground Used as return line for receive and transmit lines
3
RX Power Used to deliver relatively low currents (up to 3 Amp)
to the radio, mainly for the receiver circuitry