WHY? All signal transmitters, including CB radios require a tuned antenna system. Best performance is achieved when the output circuit of the CB radio “matches" the system. The system includes the coax cable, the antenna mount, the antenna, and the vehicle.
WHEN? All CB antennas should be tuned when they are first installed or if your customer complains about poor transmission distance.
WHAT? To tune a CB antenna, you will need an SWR meter and a short (2 to 3 feet) coax cable with PL- 259 connectors at both ends.
WHERE? All testing must be done in an open area. Stay at least 20 feet away from buildings and never perform tests in a garage or carport. The doors, hood, and trunk of the vehicle must also be closed. Oversight of these recommendations will result in inaccurate readings.
HOW? The SWR meter must be placed in line behind the CB radio. Check the instruction manual that came with the meter. Measure and Record the SWR on channels 1 and 40. This information will determine the need for tuning as well as the steps to take.
WHEN NO ADJUSTMENT IS NECESSARY
If measurements are below 2.0 to 1 on both channels 1 and 40, it isn't necessary to make any adjustment unless you want to fine tune the system to balance the SWR at both ends of the frequency band. However, keep in mind that if the SWR, regardless of the reading, is the same on channels 1 and 40-adjustment to the antenna will generally have a negative effect.
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Special Note: Since it is generally easier to reduce the physical characteristics of the antenna, all of our fiberglass CB antennas are made on the longer end of the specifications. If any tuning is required, 98% of the time this will entail a physical reduction. In any case, the ultimate goal is to achieve an SWR reading below 2.0 to 1 on any and all channels from 1 to 40. |
WHEN THE ANTENNA IS TOO LONG
FIBERGLASS WHIPS:
If the SWR on channel 40 is greater than that on channel 1, then your antenna is considered to be TOO LONG and a REDUCTION of physical height will correct this situation. To do this, simply remove the tip of the antenna and out off a 1/4" at a time until the reading is acceptable. Also, making short slits in the plastic covering of the antenna and unwinding and clipping off the wire works well.
BASE AND/OR CENTER LOADED STEEL ANTENNAS:
If our steel series of antennas shows TOO LONG, simply loosen the set screw on the side of the "whip holder" and lower the whip into the coil 1/4" at a time, tighten the screw, then take SWR reading.
NOTE: If the whip "bottoms out" before satisfactory SWR is achieved, out off 1/2" from bottom of the stainless steel whip and make final adjustment 1/4" at a time.
WHEN THE ANTENNA IS TOO SHORT
FIBERGLASS WHIPS:
If the SWR on channel 1 is greater than that on channel 40, then your antenna is considered to be TOO SHORT and INCREASING the physical height will correct this situation. Because Everhardt CB antennas are made extra long, readings, which indicate “short” normally, stem from ground plane deficiency (lack of vehicle metal surface for the antenna to reflect it's signal from). This condition is often corrected by adding a spring to increase the physical height.
BASE AND/OR CENTER LOADED STEEL ANTENNAS:
If our steel series of antennas shows TOO SHORT, simply loosen the set screw on the side of the "whip holder" and pull out the whip from the coil 1/4" at a time until satisfactory SWR is achieved.
DUAL ANTENNAS
Measurements and determination of short or long conditions are the same as the single antenna procedure. However, when tuning co-phased antennas, it is possible to adjust both antennas in equal amounts to keep them in perfect balance.
NO METAL - "NO PROBLEM"
See our full line of " No Ground " plane CB antennas (Pg. 8) designed especially for MOTOR HOMES, FIBERGLASS TRUCKS, vans, motorcycles, and boats. These antennas work "even if you hold it in your hand"!!