Icom IC-201 Instruction Manual page 6

3.5
If ап AC power supply other than the matching IC-3PU is used, be sure it is adequately
regulated for both voltage and current. Low voltage while under load will not give
satisfactory results from your transceiver. Receiver gain and transmitter output will be
greatly impared.
If supply voltage happens to decrease to less than 10.5V DC, the operation of the receiver
will be suspended in order to prevent misoperation. This indication will be shown by the
center meter light going out. —
Inserting the IC-3PU in the transceiver automatically switches. the supply source from
external to the IC-3PU. The IC-3PU must be removed from the transceiver when a DC
power supply is used.
Included with your transceiver is a DC power cord with plug attached. The RED wire is
positive (+), the BLACK, negative (—). If your mobile installation permits, it is best to
connect these directly to the battery terminals. This arrangement eliminates random
noise and transient spikes sometimes found in automotive accessary wiring. If such an ar-
rangement is not possible, then any convenient B+ lead in the interior of the vehicle and
the negative frame can be utilized. Your transceiver provides an internal DC filter that
will take out most of the transient noise. Remember, the unit operates on a negative
ground system опју. It cannot be used in a positive ground automobile. After making
- your connections, simply insert the plug into your transceiver.
_ ANTENNA
The most important single item that will influence the performance of any communica-
tion system is the antenna. For that reason, a good high quality gain antenna of 50 ohms
impedance is recommended for fixed or mobile use, presuming low VSWR, of course.
When adjusting your antenna whether mobile or fixed, by all means follow the manu-
facturer's instructions. There are some pitfalls to be aware of. For example, do not at-
tempt to adjust an antenna for lowest VSWR when using a diode VSWR meter not
engineered for VHF applications. Such readings will invariably have error of 40% or
more. Rather, use an in line watt meter similar to Drake WV-4 or Bird Model 23 with
VHF cartridge. Further, when adjusting a mobile antenna, do with the motor running.
preferably above normal idling speed. This will insure proper voltage level to the
transceiver.
Do not become alarmed if your transceiver fails to transmit at times during the antenna
tune-up procedure. Remember, your transceiver has a built-in Automatic Protection
Circuit (APC) that will disable the transmitter if excessive VSWR, a short coaxial line or
connector, or other antenna deficiency is present. A quick check on a good 50 ohms
dummy load will show the transceiver to be working. The difficulty will че with the
antenna or its transmission line.