Question about Cobra 29 LTD CB Radio

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SWR calibration waaay off the chart

I recently bought this CB, a big upgrade from my last POS. The factory installed antenna in my truck works fine, but when I recently upgraded my antenna to an oil coil, I can't get the SWR calibration to get below three or even meet the calibration mark on the meter. I've tried shortening the antenna, but the next step would be to start snipping pieces off. (I read that somewhere) Any before someone types it first - I'll say it.... Go back to the factory antenna! ;-)

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  • Anonymous Jan 02, 2009

    I bought the same antenna for my geo tracker The swr on my 4 foot whip was a 1.2 all over the 11meter band i decided i wanted to try something a little nicer looking so i picked up a oil can type and installed it Did as the instructions said Put it all the way down as most cb antennas are to long. Then it said do an swr check and i did it was a 3 on 1 and a 3.5 on 40 so i cut a 1/4 off and nothing changed so i took another 1/4 off nothing i did this 8 times a total of 2inches and still no change so I went back to the trucker stop Bought a Little will Magmount thats all they had for under 50.00 as i juist spent 80 on the oil can. I took the magnet off undid the bolt Cut a slice in the side of the plastic ran a piece of flat bar and installed it. And again my swr was high i took 1/2 an inch of the whipp 2 times at 1/4 checking the swr each time, and i got a 1.1 on 1 and a 1.2 on 40 Im happy and it runs great... The reason i never put the whip back on I had allready gave it to another guy for his truck. anyways good luck and maybe go buy a wilson

  • jlaudio12 Jan 10, 2009

    I was the one who had the same problem with the oil can... I've ran into new problems with my tracker The little will worked for about a day, So i ran ground straps everywere i could still no Fix,. I was about to light the jeep on fire but the wife stoped me, So i cooled off and got the problem fixed been running for 2 weeks off and on road and The fix was a No ground plane mobile antenna, Works great on my hr2510 and i can tune from in the cab with the slider on the coax,, I payed 17.00 for a 4 footer off ebay and it works GREAT!!!!



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Powerfull antenas require longer coax!!!!ex:Willson 5000 ,18 feet coax!!!!

Posted on Dec 23, 2009


GROUND, GROUND, GROUND! If you are running more than barefoot, you should have everything GROUNDED. 95 percent of high SWR is related to a bad ground plane with the antenna. I would run ground straps from body to frame, doors, everything. If all else falls, run a ground strap, as short as possible, to the antenna mount. It'll work everytime.

Posted on Aug 11, 2007


Double check your connections and your cable for shorted PL 259 connectors. Oil filled antenna! Humm Sham on you if you are using a liner! Oh and quit sniping the antenna remember the higher in frequincy the shorter the antenna and longer for lower in frequincy. So it could be just where the antenna is located some antennas work good there but a diferent one wont try another spot also make sure your in a clear area when checking SWR not your drive way next to the garage or house or other car and finaly use an external SWR meter the ones on the radio some times SUCK.

Posted on Jul 07, 2007

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When your raise the power in a radio, you will notice more when the antenna is not properly tuned.

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You might also want to check your coax, connections to it, and your antenna for anything wrong.

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SWR calibration waaay off the chart

You are using an inline swr meter to set your swr right, not looking at the meter on the radio? Here is the process to set swr on an antenna:

You must have an inline swr meter, which can be purchased online or from a truck stop. The ones at truck stops are cheap ones, but will do the trick for the most part.

You connect your antenna 18ft coax to the antenna plug of the swr meter, and a jumper coax (any length) to the transmitter plug of the swr meter and then to the radio.

Close all doors and make sure no one is messing around with the vehicle or antenna. You must be set up as you would normally be transmitting.

Now set your cb radio to channel 40 and your swr meter to fwd. Key up your microphone1.gif and at the same time turn the set knob on the swr meter until the needle is at the line that reads set. Unkey your mic and set the the swr meter to ref. Key up again and note what your reading is. Now leave the swr meter in ref and turn the cb to channel 1. Key up and take your reading. If the reading on ch 1 is higher than ch 40 you must raise the stinger on your antenna. If ch 1 is lower than 40, you lower your stinger. You are trying to get lower than a reading of 3 and as close to 1.5 as possible. If you lower your stinger as far into the antenna as it will go and you need it shorter, you cut the bottom of your stinger no more than 1/2" at a time, and recheck your swr reading after each cut.

Once you have gotten the best reading you can, connect your antenna directly back to the radio.

The setting of your swrs is to make your antenna as efficient as possible, by trying to get it as close as you can to a 50ohm impedance. THE ONLY PART OF YOUR SYSTEM THAT CAN CHANGE YOUR SWR IS YOUR ANTENNA, not your coax and not your radio. Your radio and coax can give you false readings, but only the antenna can actually change the swr.

On the swr meter, the fwd/ref switch stands for forward (power that is being transmitted out) and reflected (power that is reflected back into the radio.

Just for information sake, the swr cal switch on your radio is used to set the meter to reflect the swr that your antenna is set at. The meter on your radio is like a dummy light on your car. ONCE AGAIN, YOU CAN NOT SET YOUR SWR ON YOUR RADIO, only the antenna.

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