At 10:07 PM 10/22/97 -0700, you wrote:
>Concentrate on filtering the power, and make sure you have a good ground.
>
>You can't really tune a fiberglass stick, except with a matching network.
>You ought to check for an SWR (Standing Wave Ratio) greater than 1.7 or so.
>[A 1:1 ratio is ideal, 1:2.0 means half your power is just bouncing around
>between your CB and the antenna.] Get a better antenna if it's much worse.
>
Ummmmm.... not exactly true. The "antenna" in a fiberglass unit isn't the
rod, but rather the copper wire wrapped around it. Tuning an antenna for SWR
means either lengthening it or shortening it to get the lowest resistance.
On a fiberglass unit, pull the rubber cap off of the top & spread the coils
apart a bit. If the SWR goes down, keep spreading them until you reach the
lowest reading. If it goes up, push them back together & cut off 1/4 coil at
a time until you reach the lowest reading. If no SWR meter is available, key
up the mic & watch the "power" meter..... the higher the reading, the higher
the SWR. I know it sounds backwards, but you want the lowest reading on the
power meter (it's showing "reflected" power). You can also change the SWR by
changing coax length. The ideal is odd multiples of a half wave length...
18', 54', etc. Not real practicle in a vehicle, but you can get close. If
you have any excess coax, make sure it's coiled in at least a 3 foot
diameter circle.
One tip that's worked for me in the past to defeat interference....
Use base station (the thick stuff) coax to run power to the radio. Go
directly to the battery, the braided shield to the negative side, the copper
core to the positive. This shielded power cable helps keep the RF signals
generated by the ignition, alternator, etc. from sneaking into the radio
through the power cord.
Good luck.... it can be a real hassle to cure.
Maddog
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