Question about Cobra 29 LTD CB Radio

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Swr is too high and my antenna light comes on

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I need more info from you to help. What kind of antenna, what kind of co-ax and how long, also what type of vehicle is it on?

Posted on Oct 16, 2013


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Posted on Jan 02, 2017

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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

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SOURCE: 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.

Posted on Dec 20, 2009

  • 1514 Answers

SOURCE: I have the cobra 29

Normally the swr should be set on the centre channel so if you have 40 channels you should set it on channel 20. This is because as you move away from channel 20 the swr rises slightly more for each channel away from the 20. If you set it on channel 40 you'll have twice as much swr on channel 1 more than if you set it on channel 20. If the swr metre shows 1:1 (i.e. doesn't move up at all) on channel 20 the rest should be ok since the antenna was designed for CB. You should however check that the needle showing reflected power doesn't go above 2.5

Posted on Jul 30, 2010

  • 35 Answers

SOURCE: I just bought two new

After installing the antennas I normaly check for shorts. Place a ohm meter from the pin of the PL295 to gnd. If there is no short turn sel. to ch 40 and see where the match between it adn ch01.If SWR is HI on 40 the stingetrs or the top coil needs to be shorter, the opposite is for the lower chan.
If the HI swr on both ends of the spectrom it would most definately be bad connectors or could evenbe a bad ant. or both could be faulty.......Good luck

Posted on Oct 04, 2010

  • 2761 Answers

SOURCE: Can you adjust a 'rubber duck' antenna? I have a

Sorry, but each rubber duckie is cut to a specific frequency, with the actual antenna windings sealed inside the rubber/plastic outer shell. Because of this construction, there is no adjustment feature.

Posted on Nov 11, 2010

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1 Answer

Antenna light comes on only when transmitting

That is your "SWR TOO HIGH" warning light. Check the SWR of your antenna.

Feb 01, 2013 | Cobra 29 LTD CB Radio

1 Answer

CB Antenna Warning Light

Sounds like bad SWR. Check antenna ground. If mag mount, make sure mag and whe you put it is very clean. Check antenna where whip comes in to coil or base. Check pl259 with vom for continuity, open or shorts. This will probably solve the problem. DO NOT TRANSMIT WITH HIGH SWR. YOU CAN BURN OUT POWER TRANSISTOR. HOPE IT HELPS.

Oct 20, 2012 | Cobra 29 Lx Full-featured Cb Radio

1 Answer

The light for high swr keeps coming on. replaced antenna and coaxle. how do i go about lowering the swr. is there a nob or switch for this. thank you

You cannot lower the SWR via the radio. it has to do with the antenna. The length of the antenna is essential to transmitting properly. It must match the transmitting frequency.

To check SWR tune to ch 20. Flip the meter switch to CAL. Key the radio without talking into the radio. Turn the CAL knob up until the meter needle is at the CAL mark. Unkey the mic. Flip the meter switch to SWR. key the radio again, and the meter will show your SWR. We already know it is high because you are getting antenna warning, but we will have a base line now to work on.

What you did was calibrate the meter for that channel. that is necessary to check the SWR. So you must calibrate for each channel you check.

You should at least be under 2 swr. Ideal is 1.5 or under. the lower the better.

If your SWR is high, your antenna is either too long or too short. To find out here is what you do:

Check the SWR on ch 1 and ch 40 calibrating for each channel. Compare the difference of the SWR between 1 and 40. If the SWR is higher on 40 then 1, your antenna is too long. If your SWR is higher on 1 then 40 your antenna is too short. All CB antennas have a way to adjust the length.

If its a mag mount, its usually a set screw you loosen to raise or lower the whip. Fiberglass antenna's usually have something under the cap at the tip to adjust. It will either be like the mag mount, with a set screw and a small rod to raise or lower it, or a screw, that you screw in or out to make it longer or shorter.

make small adjustments. 1/8th or a 1/4 of an inch at a time. Each time you make a change, take an SWR reading on 1 and 40 again and compare the difference. The difference should be getting less. Do this until there is very little or no difference between 1 and 40.

Then you go back to 20, because it is the center channel and check the SWR there. It should now be low. If you did a good job it will be under 1.5 and you are good to go.

Aug 07, 2011 | Galaxy Radios DX-93T Base CB Radio

1 Answer

My rx/tx light is green untill i push on the mike. then the light turns red. and the antenna led theres nothing. whats could be the cause and the fix...and the swr metter goes into the red all the way to...

Its working alright then...what the antenna light is for in case the SWR is too high. If it does not come on---Then it means your antenna works good.

May 16, 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.

Oct 11, 2010 | Cobra 29 LTD CB Radio

2 Answers

Used the CAL function for the SWR. When I transmit, the Ant. light comes on and the meter is above 3. Do I need to shorten my antenae?

not necessarily. it may be electrically short. if the swr is higher on channel one than it is on channel fourty, your antenna is electrically short. if the swr is higher on channel fourty than it is on channel one, your antenna is electrically long. no matter what anyone says, all antennas are tunable. just cut the shielding back at the top of the antenna and adjust if necessary. if it is a steel whip, it should have a set screw at the bottom. if you still have problems with high swr, ground the mount to your vehicle. if you still have high swr, you might have to try a non ground plane antenna.

Sep 13, 2009 | Cobra 29 LTD CB Radio

1 Answer

Cobra 29 NW LTD Classic wont calibrate and red antenna light keeps coming on

The calibrate knob only calibrates the radios SWR meter, the owners manual will show you the procedure for that. If your ANT light is coming on, it is telling you that your SWR is to high, and may cause damage to the radio from reflected power. You should purchase an in line meter as the radios internal meter may be somewhat unreliable. You need to tune the antenna to the lowest SWR possible. Typically anything under 2.0:1 is acceptable. Radio Shack sells a meter for about $50, and is pretty accurate. Antenna mounting can also cause high reflection if it is to close to other objects. Google "CB antenna tuning" or read the instruction manual for you antenna, and you should be able to figure out how to properly tune the antenna.

Jul 07, 2009 | Cobra 25 NW LTD 40-Channels Base CB Radio

1 Answer

Antenna light comes on when trying to transmit

Its the antenna. it is not tuned correctly for the radio. First, stop transmitting. You can burn out the final transistor. If the antenna light is coming on, that means your SWR is too high,

first. Check to make sure that the antenna coax is securely attached and fastened tightly to both the radio and antenna.

Next inspect the coax. Make sure there is no damage to it. If there is a slice in it, it is kinked really bad, that could be the problem.

Now, if the coax looks good and is connected tightly, now its on to tuning the antenna. Your antenna is either too long or too short. Antenna's usually have a way to adjust this. Most common is where a metal whip sits in a collar. You loosen the collar, and you can move the whip up and down in it. That is how you adjust the length of your antenna. Fiberglas whips usually have an adjustment at the tip that you can adjust usually by screwing it in or out.

Now here is how to check your SWR.

Make sure you are in an open area like a parking lot as structures such as buildings and trees can cause reflection and give you a false reading. Always take an SWR reading with your doors and windows shut as not doing so can also cause a false reading.

Now that you are in an open area, turn on the radio and turn to channel 20. flip the switch located all the way to the left by the signal meter to CAL. Now turn the knob all the way to the right just before the channel selector marked SWR CAL all the way down to the left before you start. Now key the mic without talking into it and turn the SWR CAL knob up until the needle on the meter is all the way to the right to the mark for CAL. its a little upside down triangle with the letters CAL next to it. You want the needle to be on that triangle. Now while still holding the key in, flip the switch all the way to the left next to the signal meter up once to SWR.

The needle should swing back giving you your SWR reading. Ideally you want this reading to be as low as possible, but 1.5 and under is acceptable. If it is higher then 3 and in the RED stop transmitting. Try to do the steps quickly so you can un key as soon as possible to avoid damage to the final resistor if the SWR is higher then 3.

If the reading is 1.5 or under and the ant light is going on, it could be something else. I will go more into this at the end.

Now we have to figure out if the antenna is too long or too short. Here is how to do this.

Turn to channel 1 and repeat the steps to take an SWR reading. Make note of the reading.

Turn to channel 40 and repeat the steps again to take an SWR reading. Not that number.

If the SWR is higher on channel 40 then channel 1, then your antenna is too long and you need to adjust your antenna so it is lower.

If the SWR is higher on channel 1 then on channel 40, then the antenna is too short, and you need to adjust the antenna higher.

If the signal is over 3 on both channels, then there is something wrong with either your coax, antenna or both, and you should replace the coax, and if its still high, the antenna.

If your antenna is too long or too short, make adjustments to correct. Raise or lower the antenna a 1/4 inch at a time. each time taking a measurement to see if it is still to long or too short. You want to try to get the SWR the same on 1 as on 40. And channel 20 will have the lowest reading.

If your SWR reads low, under 1.5, or even a 2, the light should not come on. If you have had the radio worked on at a radio shop, or purchased it from some where that modifies the radio to put out more power before they sell it, then that can cause that light to go on falsely. Purchase an external SWR meter. You can get one off ebay, or from radioshack. Check the SWR with the meter, and if the SWR is still good, then you can do 1 of the following.

1. ignore the light because it is not right.

2. go in the radio and try to adjust VR6 so that the light doesn't go on. Not recommended if you don't know what you are doing.
3. take it to a cb shop and have them adjust VR6 for you.

I would leave it alone.

Most likely your antenna is not tuned properly.

Apr 26, 2009 | Cobra 29 LTD CB Radio

2 Answers

ANT indicator

Something in your antenna setup is causing high SWR reflected back into the radio. Antenna could be ungrounded? Have you tuned that antenna? Any part of the coax broken or pinched in a door? Where is he antenna located on the vehicle? Are you parked under or near a metal building? All of these things can cause high SWR reflect. Let me know if you need help in tuning your antenna or getting it set up.

Jan 10, 2009 | Cobra 29 LTD CB Radio

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