Question about Cobra 29 LTD CB Radio

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Swr too high

I have dual antennas on my semi, (factory), one is mounted into the original factory mirror mount, the other is on an after-market mirror bracket. After calibration, (cobra 29), my best swr is about 2.5. Do
I need better ant. or is there a grounding problem, or something else? I would like to increase both transmit and reception.
It is worth having the radio, "peaked and tuned", and if so how much should I expect to pay.
Thanks for your help!

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  • 44 Answers

Check your antenna. Make sure it is getting a proper ground. Check where whip goes into coil or base. Make sure all allen screws are tight and whip is not either all the way down to the base or up to the top. If antenna is mounted; make sure that it has a good ground. You might have to remove some paint around the base to get a good connection. DO NOT TRANSMIT WITH A HIGH SWR. YOU CAN BURN OUT THE EXPENSIVE POWER OUTPUT TRANSISTOR. Hope it helps.

Posted on Apr 27, 2014


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Posted on Jan 02, 2017

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SOURCE: CB transmission

Hello 64driver,

Make sure the radio is grounded properly and that the SWR is around 1.2:1, 1.3:1 is good but try to get it to 1.2:1. Also take a power output reading while keying the mic. To do this with your power meter put it in-line with the CB and your antenna and key the mic you should get about 4 to 5 watts PEP. If this is the case your unit is putting out the proper power level, if not have the power amplifier checked by a qualified repair shop.

I hope this helps


Posted on May 14, 2008

  • 3 Answers

SOURCE: Cobra 29 LTD Classic not transmitting or receiving

ant. light should only come on if you have a high vswr a bad thing did you check that cb/pa switch is set to cb check your swr this is not a good place to mount ant. as it is close to metal of back of cab

Posted on Dec 24, 2008

  • 1 Answer

SOURCE: Cobra 29 LTD Classic not transmitting or receiving

As I understand from a tech friend of mine, most truck beds are not grounded well enough. Perhaps you could borrow/purchase a magnet mount antenna and locate it on the roof, for testing. Then you would have it narrowed down to the location.

Posted on Jan 07, 2009

  • 7 Answers


the problem is in the antenna cable. the lenth of a antenna cable must be divisable by 3. try replaceing cable with a 18 foot cable that should fix the problem.

Posted on Apr 22, 2009

  • 773 Answers

SOURCE: Reception is very poor. Grounding issues? Please

Reception has little to do with grounding. The ground plan is for transmitting. As long as the coax is connected and is in good standing, it should receive fine regardless of grounding.

There are a few reasons you may have bad reception.

  1. Turn the RF GAIN all the way up. This is your receive sensitivity.
  2. Squelch is too high. It should only be turned up enough to cut out the background noise.
  3. Poor antenna. If the antenna is cheap, and not made well, this could be the problem.
  4. Not enough of the antenna above the vehicle. It needs to be at least 60% of the antenna above the vehicle.
Hope this helps!

Posted on Oct 21, 2009

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2 Answers

I just bought a cobra 29 LTD Chrome along with a 102" whip and spring. Best place to install antenna on semi dump truck? Suggestions? And how critical are your surroundings when tuning the antenna?

what kind of truck? does it have a fiberglass body? If it does then you would have to go directly to the chassis to mount the antenna.If you got a different antenna , like a Wilson 2000 , you could either run it co-phased or single. you would have to get mirror mounts and coax or buy a kit that has it included . Tuning a single antenna is easy but a twin is harder to do. you have to tune each antenna individually. what you also have to do is stay clear of buildings, overhead electrical wires ( high tension ) and metal objects. Now we know this is impossible so just get the SWR down as low as you can and also make sure your doors a both closed when checking the swr.

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Measure out your coax in 3ft intervals. Like if you need 7ft use a 9ft length of coax. Also make sure your mirrors are grounded use a external swr meter as well, the internal swr on the galaxy could be off. .

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I am having a problem with mt cb. I used all new coax, antenna, antenna stud and mount. New mic and radio. The problem is I hook up the swr meter, keyed and the meter swung hard right. I have changed

ok, you have a high SWR.. this is what you can do.. you're gonna need to check the Radio's coax connection to see if it's loose on the Radio itself.. you're gonna have to open the Radio cover on the speaker side.. now go look at the connections on the pc board itself and see if there is a possible broke connection.. one is pcb ground, and one for the center. also, you might want to get a phillips head screw driver and gently tighten all the screws on the pc board. becareful going in there.. after this said and done, check the antenna connector itself to see if it's loose. if so, then you're gonna have to a pair of pliers to turn the nut on the inside while you use wrench to hold it in place on the outside.. now you're ready to test the radio.. don't put the cover on just yet until you see the results. set up your SWR Meter to the Radio and then set up the dummy load and do a SWR Test. if the reading is good, then the Radio is all set.. now for the Antenna.. you said that it's all new, but regardless you need to test it too.. check both ends of the cable and do a condinuity test.. get a ohm meter that has an audio sound. this will help you.. set the meter to ohms/conditnuity.. then short out the probes to get a ZERO reading/audio sound.. now take one end of the of the cable and put the probes on the connector.. one probe for the outter ground shell and the other probe to the center pin connection. if you see a ZERO reading or an audio sound, that means you have a short in the cable.. another way is to do it end to end.. put one probe on one end of the cable, and the other probe on the other end.. test the ground side first.. if you get a sound or a ZERO reading, that means you may have a short in the cable itself and may requier to remove the connectors.. some cases you might have to replace them.. remember to calibrate your meter when testing let me know how it goes.. I'll continue to help you.. you can contact me on Facebook.. Good Luck..

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I have a wilson 5000 mirror mount. I mount it on the drivers side mirror on the upper cross arm that goes to the mirror. It is mounted on this arm with a bracket and a so 239 connector so I can undo it if I have to ,leaving the antenna connected.I can change coax and not have to worry about undoing the antenna. Remember one thing. The antenna has to be checked for SWR.each time you move it to a different spot or to a different truck.

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Make sure the antenna is installed correctly. and away from any metal.. Make sure the insulating washer is on top of the mirror mount.. and that the ground is connected to the ground of the coax.. do not isolate the ground from the mount. Anything near it like a smoke stack,pick-up truck cab, headache racks, vertically near the antenna can change the swr's. Next you would have to adjust the antenna's whip for correct swr's, and depending on location of antenna it would have to be shortened or made longer... ie use a spring or longer whip/shaft to increase the length.. there are many factors on high swr's issues. best way is to see it to fix the problem.

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1 Answer

I have a cobra 25 nw st and i do not have a swr meter. how do i tune it to the antenna. the antenna will be used on several trucks.

You really should have or borrow a meter for this task. Just tune it for the for the lowest SWR, mounted in the position it will hopefully be mounted on all the trucks. I presume you are a Trucker, and will be placing on another Tractor, with a similar or West Coast mirror style mount. Let us know how this works out on the various vehicles. Thanks, Bill

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Setting SWR Wilson 5000 magnetic mount antenna. Started with a reading over 10, reduced it to just under 7 by reducing the hight of the whip, should I check the pl259 connector and check the coax for...

Your antenna is probably still to long. You need to do a few things to see if your antenna is too long or too short. Here is a link to something I found that is very informative, and a post on how to do what you need to do. there is also a thread on the site that has common problems for high swr.

here is common problems for SWR

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I set the swr on my antenna and it keeps moving i have a cobra 19 dx iv and i just installed a net window mount antenna 27" on my back window that has factory tint.

1) if you are talking, your SWR will most likely move. You must take the reading while not modulating, (talking into the mic)

2) Window mount antenna's are GARBAGE. they are worthless. BAD BAD BAD. You wasted your money. Get a mag mount.

3) if you are not in an open lot, your SWR's will be different due to structures reflecting signal back. Always take your SWR reading in an open lot.

4) You could be experiencing Common mode currents. Normally the signal travels on the inside of the coax ground. Common mode current is when the signal is traveling back down the coax on the outside of the ground in the coax. (The biggest cause of this would be the window mount antenna). If you want to keep that garbage antenna, then you can make an RF choke in the coax. The best solution is get a better antenna. Here is how to make the choke. As close to the antenna as you can, take 6 ft of coax and loop it uniformly laying each coil next to the other. use electrical tape to hold it in place. You want 6-8 wraps. You want a nice uniform coil.

Just get a better antenna. Window mounts are the worst. You get horrible receive and horrible transmit. Get a wilson 500 mag mount. It will work so much better for you.

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1 Answer

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You Need to check and set you SWR on the antenna system. You may also have a bad coax or the ant studs ( mounting hardward ) for the antennas may be bad. It definally sounds like an ant/coax problem Good Luck
NC Electronic
Mills, Wyoming

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