Question about Cobra 29 LTD CB Radio
RX/TX light should change to red, however the ANT light is a bad light. This means that your antenna is not adjusted properly. Do not key the radio or talk on it for any other reason then to check the SWR and tune the antenna. If you have the manual that came with your cobra 29, there is a section that explains how to check the SWR. And the manual for the antenna, it will explain how to adjust it.
If not, here is how to do it.........
How to check the SWR on a Cobra 29
Step 1. Find out what your current SWR is on the center of the band.
The ANT light may come on with an SWR of 2. running the radio with an SWR of 2 shouldn't hurt the radio, but I don't like to mess around. Get it as low as possible.
How to adjust the antenna for SWR
The length of your antenna will change your SWR. SWR is basically how much RF energy is not leaving the antenna and getting reflected back into the radio. That's why it hurts the radio when its high. An antenna has to be the right length, matching the length of the radio waves in order for it to radiate all of the RF energy out of the antenna.
Most antennas have a way of lengthening or shortening the antenna. If its a mag mount antenna with a metal whip, there is probably a set screw that when loosened, will allow you to raise or lower the whip. If its a fiberglass antenna, under the rubber cap at the top is how you raise or lower the antenna.
Figuring out if your antenna is too long, or too short
Here is how to know weather or not you have to lengthen or shorten your antenna.
If the SWR is higher on channel 40 then channel 1, then the antenna is too long. You need to shorten it.
Make small adjust ments about an 1/8th to a 1/4th inch at a time. each time checking the difference between channel 1 and 40.
You will know when you are a good match when there is little to no difference between channel 1 and 40's SWR. Once you are satisfied that the difference between 1 and 40 is about the same, and much lower, then turn the radio back to channel 20 and take an SWR reading.
You will now find that the SWR on channel 20 is really low. Most likely under 1.5 or better, Almost nothing on the meter.
Here is a Meter Key, so you know what you are looking at.
Posted on Oct 11, 2010
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Posted on Jan 02, 2017
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