Micom 3T Operations Instructions download pdf (Page 141)

Installation

123

DC Power Connector

The DC power connector located on the rear panel of the radio is used to provide power to the

radio. Table 6 lists the functions of the DC connector pins.

Table 6. DC Power Connector, Pin Functions

Pin Designation Description

1 TX Power Used to deliver high current to the radio (up to 28A),

mainly for the transmitter circuits

2 Ground Used as return line for receive and transmit lines

3 RX Power Used to deliver relatively low current to the radio (up to

3A), mainly for the receiver circuits

Vehicular Noise Reduction

Most vehicles contain several noise sources which can greatly disturb radio reception. The most noisy

sources are the high voltage ignition sparks that are produced at the vehicle's plugs. The second is the

alternator activity.

In keeping with the following installation practices and if necessary by adding some damping

components, it may be possible to reduce these noises to a tolerable level.

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 Amp capacity batteries) by passing

the noise to ground.

3. If necessary, connect 0.01 – 0.1 microfarad 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 a

such a wire.

6. The RF noise reduction kit for alternator equipped vehicles (TLN8845) includes some useful

accessories for noise reduction. Among them being the resistive ignition coil suppresser cable.

In severe noise conditions, you may find this kit helpful.

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Micom 3T Operations Instructions Page 141