High SWR

This right here tells me your antenna is too short. You need a longer antenna. Or if you have a tunable tip, raise the tip until you get a 2.0:1 (at the minimum) across channels 1, 20 and 40.

Or...if all you ever needed to use was a particular channel (i.e. 19) you could tune to get a low reading on 19 only, but IMO why, if you have another 39 to tune from.

Also are you running an export style radio with the band switch on the front? If so ensure you're not on anything but the CB frequencies (26.965-27.405) as this can cause SWR problems when trying to run a CB style antenna.

 

Some antennas (usually very short ones) may not be able to cover all 40 channels with a sufficiently low SWR. In that case, you would tune it to cover the channels you want to use.

Side note: When you factor in the RC channels, channel 19 is in the center of the CB band. ((26.965+27.405)/2 = 27.185; channel 19.)

 

Something that many radio people never talk about is the importance of a good ground. In the world of small power such as a CB (12 watts pep), a good ground is critical. In short, your ground can never be "Good enough". So, start there and work backwards through the antenna to the radio.

 

When you stated you adjusted the antenna, did you do so in small adjustments?

Only adjust it one, maybe two turns at a time and recalibrate the SWR meter each time you check to be sure you are accurate.

As you lengthen the antenna tip and check make sure you note the reading each time. If the SWR starts to go down, you are on the right track. During the adjustments, if you have been getting low SWR then it starts to raise again, stop and back the tip down a half turn until it is at the lowest SWR again and you should be done. Anything under a 3 will be ok