Radio Shack TRC-446 - Manual (Page 9)

9
Public Address Speaker
To connect a PA speaker to the CB, use
an 8-ohm speaker capable of handling 5
or more watts of power and equipped
with an
1 /
8
-inch connector on the cable.
Contact your local RadioShack store
for a selection of suitable speakers.
Plug into PA SP. See “Using the Public
Address Function” on Page 14 for oper-
ation instructions.
ADJUSTING THE
STANDING WAVE RATIO
Most antennas are factory adjusted.
However, you can usually improve per-
formance by matching the characteris-
tics of your antenna system to the CB's
RF output power using the built-in SWR
meter. The impedance of a CB’s output
compared to the impedance of the an-
tenna and the antenna cable is typically
slightly mismatched. By adjusting this
impedance ratio to be as close to 1:1 as
possible, you maximize the efficiency of
your system.
After you have properly installed the an-
tenna and routed its cable, follow these
steps to adjust the standing wave ratio
Note: The SWR on some mobile and
base-station antennas cannot be
changed.
1. Turn on the CB by turning OFF/VOL-
UME clockwise until it clicks.
2. Set S/RF/SWR/CAL to CAL .
3. Hold down the microphone's talk
button and adjust SWR CAL so the
SWR/RF signal meter's needle
points to CAL on the upper SWR
scale.
4. Release the microphone's talk but-
ton.
5. Set S/RF/SWR/CAL to SWR .
6. Press the microphone's talk button
again and note the actual SWR
measurement on the upper SWR
scale. See the chart on Page 10 for
help in interpreting the SWR meter
readings.
The SWR value takes into account the
actual frequency of the RF signal trans-
mitted. Therefore, you will get a different
SWR reading from one CB channel to
another. Almost all the CB transmis-
sions usually fall within an acceptable
range. However, for optimum radio per-
formance, we recommend that you fine
tune the antenna's system based on the
channel you use most. If you have no
particular channel preference, set your
antenna's SWR for maximum perfor-
mance on Channel 19.
21-1574.fm Page 9 Thursday, May 13, 1999 4:03 PM