I know I have spoken about this before, but it seems I need to revisit the matter. I got an email asking if an antenna would need to be retuned to match a new radio. Here is the simple answer: no. You won't need to retune your antenna to work with your new radio.

An antenna is tuned to the truck, not to the radio. So, whatever radio you install will work with a properly tuned antenna. I know that dealers make a lot of money by retuning the antenna to match the new radio they just sold to you. The truth is that the antenna is tuned to work with the truck, and the radio is the instrument you use to make sure the antenna is working efficiently.

The simple explanation is, SWR is a mathematical formula that tells you how efficiently your antenna is working. As in my SWR is 1 to 1. This only means that you gave the antenna one watt and one watt radiated off the antenna and zero was reflected back in to the transistors of the radio. That is 100% efficiency. We never get that close, but you can get close. The more efficiently your antenna radiates the power you give it, the better it is going to work.

Most radios, like a 20 Cobra, have a SWR meter built into them. You can test the efficiency of your antenna by using this meter. First, go to a channel that won't disturb others. We usually use channel 20. It is the center of the CB band. Slide the SWR/SRF/RF power switch to the CAL or calibrate position. Key up the radio. Then turn the calibrate knob until the indicator in the meter window reaches the infinity mark (sometimes a diamond in upper right-hand corner of the meter). Then un-key. You have now calibrated the meter to the power your radio is putting out.

Move the switch to the SWR read position. This is indicated by the letters SWR. Then key up the radio. The needle should just bump and drop back. The further up the indicator goes, the less efficiently your antenna system is working.

Do remember that no matter what you do with knobs and switches, the SWR will not change. In order to change the SWR, you need to do something with the antenna system.

And that, friends, is a subject for another article.

This article is provided by Truckstop Electronics, Inc. Stan Wells has been involved with repairing and selling CB radios for over 30 years. He's also involved in product development and testing. For more information visit http://thecbshop.com/ or email Stan at cbshop@layover.com.