Question about Cobra 29 LTD CB Radio
Posted by Anonymous on
1. You calibrate the antenna to match the CB rather than the other way around. Some antennas can be adjusted while others cannot. This should not cause a problem since the ones that cannot be adjusted generally don't need adjusting. The ones that can be allow for fine tuning to get a better match.
2.To match your antenna to your CB you set the SWR (Standing Wave Ratio) to it's lowest possible setting. SWR is the ratio of power that gets out through your antenna versus the reflected power that gets sent back to the CB. You want to get the most power to go out, or forward, through the antenna as this drives the signal that others receive. To set your SWR;
3.Connect an SWR meter between the antenna and the CB using a short piece of Co-ax cable. Set the switch on the meter to Forward Power. Key the CB and adjust the dial on the SWR meter until the needle of the meter is fully forward. Release the transmit button and change the switch on the swr meter to Reflected Power. Key the mic again and note how high the needle goes. If the needle doesn't go into the red it's safe to use but the lower the reading the better.
4. To bring it down check your antenna. Some antennas have a telescopic tip that can be extended or reduced by loosening a nut near the top. Try extending it fully and repeat the procedure at paragraph 3 above. If your SWR rises then try reducing the antenna length and check again. It's a matter of finding where you get the lowest swr by making smaller adjustments from the best of the 3 settings above.
5. You'll probably find that when you get a low SWR on one channel it will be higher on other channels. This is because of the frequency difference. Unless you use one channel nearly all the time, it's best to set the swr on the middle channel so if you have a 40 channel CB set the SWR on channel 20. The further you change up or down the higher the SWR will increase but it should be still within the safe range. If you set the SWR on say channel 1 the SWR will be twice as high when you change to channel 40 than it would have been if you set it on channel 20.
6. Most people never check their SWR so if you're using a commercial CB antenna, rather than a home made one, it should be factory set to give a reasonable match so if yours cannot be adjusted it's probably matching ok. A more common problem to look out for is the connection from the antenna to the CB. Make sure that the screening wire and the centre core are not touching. Even a single strand of the screening touching the centre wire will cause screeching on your transmission and before long will cause your CB to stop working. 73s and enjoy your CB.
Posted on Apr 03, 2011
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Posted on Jan 02, 2017
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