Setting the SWR
All CB antennas are tunable. Antennas that have an easy, often
mechanical, tuning device are referred to as a "tunable antenna".
Accordingly, lots of people think the other antennas are not tunable
and so they make no attempt to have the antenna tuned. This is a
critical mistake.
Wire-wound antennas without mechanical tuners, that test electrically
long (higher SWR on ch 40), can be tuned by removing wire from the
top. Remove the antenna cap, remove one wrap of wire and cut it
off. Recheck the SWR again. As long as the SWR is higher on channel
40 continue to cut. Do not cut more than one wrap at a time. If
SWR testing indicates the antenna is electrically short (higher
SWR on ch 1), the coils at the top of the antenna can be separated
and spaced further apart or accessories that increase the physical
length of the antennas (springs, quick disconnects) can be added.
Solid fiberglass antennas (straight or helical wire impregnated
in fiberglass resins) that are electrically too long (higher SWR
on ch 40) can be cut shorter with a hacksaw or grinder. Cut only
1/4 of on inch at the most at one time. If the SWR test on one of
these antennas indicates that it is electrically short (higher SWR
on ch 1), the addition of a spring or quick disconnect (or both)
is the only way to correct for the short condition.
Base loaded antennas with wire whips have a set screw (or two)
just below the area that the whip is inserted into the loading coil.
By loosening up the set screw(s) you are able to slide the whip
up or down as required. If the SWR is higher on ch 40 slide the
whip down, If the SWR is higher on ch 1 raise the whip.
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