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Swr gagde doesnt light up - Cobra 29 LTD CB Radio

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Just a matter of replacing the bulb this can be found on the top of the metre you can remove one from another radio it will acheive the same result good luck

Posted on Dec 03, 2010

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1 Answer

Cb antenna warning but the antenna passes check?


You need to check the SWR on your antenna. Use a SWR meter to do so if the radio doesnt have one internally.

Jun 14, 2013 | Radio Communications

1 Answer

I just mounted a dual antenna set to the bed of my pick up.. i took a grinder to the underside of my bed to get a good ground to the metal...my cb turns on and i calibrated it just like i always do... i...


You need somebody with a swr meter to calibrate the installion, if your antenna light is coming on the swr readings are to high and you risk blowing the rf transistor in the radio.

May 08, 2012 | Cobra 29 LTD CB Radio

1 Answer

My ANT light comes on when ever i push the mic button but my SWR isnt that high


The meter will be more accurate and an external meter will be even better. If they show good disregard the ant light it is adjustable. It may have been set to sensitive from factory. These erroneous SWR reading can be the side effects of a PEAK & TUNE if the coils have been spread but that should also show on meter.
SWR meter calibrations
  • Switch (S/RF SWR CAL) to the CAL position.
  • Push and hold mic button
  • While holding mic button adjust the SWR CAL knob so the meter needle swings to the CAL mark on the meter
  • While still holding down the mic button, set the (S/RF SWR CAL) switch to the SWR position, to read the SWR reading. Note: When switched to SWR position the meter needle should ideally be as far to the left as possible. Anything over 3 is not acceptable.

Jul 28, 2011 | Cobra 29 LTD CB Radio

1 Answer

I've got a Cobra 29 with WX and BT, the antenna light comes on, the swr meter barely moves and it doesn't seem to send or receive, still gets weather. May have been run with a bad antenna, got a new...


Please make sure you are tuning the antenna correctly.



It is important to tune your CB radio antenna to the proper length. The length must exactly match the wavelength of the frequency you transmit on. Or be really really close.

All Cb antenna's have a way to adjust the length of the antenna. If it's a mag mount, the metal whip can be slid in and out of a metal collar. Usually a set screw. If its a fiberglass whip, the way to tune it is on top. It either has a small metal rod with a set screw to adjust the length, or it threads in and out to adjust length.

Either type you have it will need to be adjusted for proper length. Here is how to tune the antenna to lowest SWR.

Some radios have a built in SWR meter. Some do not. If yours doesn't have an SWR meter, then you have to use an external SWR meter. Radio shack carries one, and you can find them cheap on ebay.

If you have a built in SWR meter or external, the procedure is the same:

1. Turn the radio to CH 20.(This is the center of the band.)
2. Switch the meter switch to CAL. (CAL stand for calibrate.
3. Key the radio. (Important. Do not talk while keying the radio.)
4. turn the CAL knob up until the meter hits the CAL mark.
5. Now while still keying the radio flip the meter switch to SWR.

Where the meter falls after that point is you SWR reading. If its above 3, that is real bad. 2 is not gonna kill your radio but its not the greatest. 1.5 and under is a good place to be, but the lower the better.

If your SWR is high, Here is how to find out if your antenna is too long or too short.

1. Turn to CH 1
2. Repeat SWR procedure. You must calibrate every time you do it.
3. Remember the SWR reading.
4. Turn to CH 40.
5. Again repeat SWR procedure.
6. Compare the reading between CH 1 and CH 40.

Now if the SWR is higher on channel 1 then channel 40 your antenna is too short. You must make it longer.

If the SWR is longer on channel 40 then on channel 1, then the antenna is too long, you need to make it shorter.

Make height adjustments about an eight inch at a time, and take reading each time.

once the SWR is significantly lower and the reading on channel 1 and 40 are about the same, you a about matched. At this point turn the radio to the center of the band, channel 20 and take an SWR reading.

You should now have a low SWR reading, 1.5 or under. If you are 1.5 or under, you are good to go.

If you cannot get the SWR to an appropriate level, there may be an antenna problem.






Now: If you have adjusted the antenna properly and you still get the antenna warning light, then the antenna warning circuit may be out of whack. Use an external SWR meter.

You may also be getting common mode current. Its when RF comes down the outside of the coax. If the swr goes up with modulation then it's common mode.

Here is how to stop common mode.

As close to the antenna as you can while still inside the vehicle, take about 6 to 8 inches of the coax, and coil it up into tight even coils and secure into shape with electrical tape.

This is an RF choke, and will stop the common mode current.

If all other radio's are fine and no ant light come one, and are all showing low swr, then turn VR6 back to disable the ant warning light. "only do this if the ant light comes on when SWR is lower then 1.5 and does not swing up with modulation showing that the ant warning light is miss aligned.

Nov 07, 2010 | Cobra 29 LTD CB Radio

1 Answer

Every time I press my MIC to speak into it the red lights on the RX/T and ANT light come on alerting me of a problem. How can I fix this.


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.

  1. Turn the radio to channel 20.
  2. Set the S/RF SWR CAL switch to CAL.
  3. Turn the CAL knob all the way counter clockwise.
  4. Key the radio. Do not talk into the mic.
  5. While holding the mic key, turn the CAL knob to the right until the needle reaches the CAL mark on the top right of the meter.
  6. Now flip the S/RF SWR CAL switch to SWR while still holding the key on the mic.
The needle should fall. Where ever the needle is while holding the key is your SWR reading on channel 20. It should be as low as possible. If its a reading of 2, then its not gonna kill the radio but is border line. Any higher and its bad. Using the radio like this will damage the final output transistor. If its less then 2 this is better. You want it to be less then 1.5 or better.

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.

  1. Take an SWR reading as explained in the first step on channel 1. Write down the SWR for reference.
  2. Take another SWR reading on channel 40. Again write it down for reference.
Now if the SWR is higher on channel 1 then on channel 40, its too short. You need to make it longer.

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.
2d03348.jpg

Oct 11, 2010 | Cobra 29 LTD CB Radio

2 Answers

When I key my mike my antenna light comes on


Hi, my name is John. ..On some radio,s that is normal, however, Have your SWR checked to be sure. They can do this at Radio Shack for free or some CB shack.... hope this was helpful...

Aug 31, 2010 | Cobra 29 LTD CB Radio

1 Answer

Cobra 29 nw when you key the radio the swr meter doesnt move and if you move the swicth to cal you can adjust it with out keying the mike but has good recive any help would be good thanks dwayne


To check the SWR, you put the swicth on CAL and key the mike with mike gain turned down all the way,then calabrate it to the meter on the CAL scale,then swicth it to SWR before you unkey the mike, then what ever the needle falls back to, that is your SWR reading.

Apr 26, 2010 | Radio Communications

1 Answer

My antenna light stays on even after I have realeased the mike


Try checking the SWR's on channel 1, 20, and 40. The SWR's will change from the low channels to the mid channels to the high channels. The key is to make sure that the SWR's are around 1 or less at all three points. If the light goes out when checking one of them, then the problem is most likely the SWR's. If the light stays on when checking these channels, the issue might still be the SWR's but I would look at the grounding on the antennas. When holding the talk button on the mic and switching from calibrate to swr, can give a false reading. This is due to the calibrate circuit remaining open until you release the talk button. Take the SWR reading by releasing the Talk button on the mic after calibrating then pressing the talk button again after switching back to SWR. This will be the most accurate reading. From everything you described, I would be looking for a grounding problem with the antennas or coax, possibly even a rub though on the coax somewhere in the dash.

Dec 20, 2009 | Cobra 29 WX NW ST 40-Channels Base CB...

2 Answers

When i key up the mike the tx/rx light and the ant


your swr setting are off wack fix your swr

Oct 02, 2009 | Cobra 29 LTD CB Radio

1 Answer

The ant light and the other light light up red when i key the kic


the tx/rx liight is green when your radio is recieving signals and turns red when you are sending signals. the ANT light is red when your SWR is too high (over 3)

1. turn the knob labeled swr cal all the way counter clockwise
2. set the rf swr cal switch to the CAL position
3 key up the mic and hold it while you rotate the swr cal knob until the needle reaches the swr cal postition
4. set the swr cal rf switch to the swr position
5. key up the mic while on chanel one (record the the number)
6. switch to chanel 40 key up the mic (record the number)
if the number on chanel one is lower than the number on chanel 40 then your antenna is too long.

Sep 14, 2009 | Cobra 29 LTD CB Radio

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