Question about Cobra 29 LTD CB Radio

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My Cobra 29 LX receives including the weather but can't transmit

My Cobra 29 LX receives including the weather and when I keyed the MIC, I can see the meter go up and down but it seems people can't hear. Display indicates everything working. Can it be my MIC or did I blow my finale?

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  • 1,212 Answers

If the relay contacts are closing. You may have blown the output transistor, however a broken wire in the microphone can also create the symptoms you describe. .

you can check by using a #47 light bulb soldered to a PL259 connector as a dummy load. If it lights, the carrier is present, but you may not have voice modulation which will show as differences in light intensity as you speak. If no modulation, the microphone is the first thing to look at.

The relay contacts may also be very pitted or corroded and not achieving continuity.

Posted on Feb 19, 2012

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Posted on Jan 02, 2017

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  • 773 Answers

SOURCE: 29 cobra ltd c.b. wont transmit or receive

make sure the RF gain is all the way up, and the dynamic is all the way up or most of the way up.

When you say the antenna is good, have you checked the SWR's and or have tuned the antenna to be the correct length for the radio? If this has not been done ever, your radio could be a brick.

Also, make sure the PA/CB switch is on CB. if its on PA(public address) it will not receive or transmit because it is on PA mode, which if you have one hooked up, a PA speaker, then you can talk to people through it out side your car.

Also, make sure the S/RF SWR CAL switch, its the first one on the left, is all the way up on S/RF. this is your signal/ receive setting for the meter. When you hold the key, does this needle swing forward? As well does the RX/TX light turn red? If it does, then the radio is transmitting.

There is another light on the radio under the TX/RX light. It is the Antenna warning light. If this light comes on when you transmit, or has come on all the time during transmit, and now it doesn't then the radio is a brick. That is a warning light. It means that the antenna is not matched, or has not been tuned to the radio. If this has not been done ever, you have killed the radio.

Here is why. When you transmit, you are sending off a radio wave. This radio wave, at 27mhz, is about 36 feet long. In order for the wave to radiate off the antenna, the length of the antenna has to match the length of the radio wave. Now it does not have to be a full 36 feet. It can be an exact multiple of 36 feet. In other words it can be 1/4( one quarter) or 5/8(five eights) of a wave in length. 1/4 of a wave is 108 inches, or 9 feet long. Your antenna is still probably does not seem 9 feet long, but there is usually a loading coil that is not exposed making up the rest of the length of antenna, so that it matches the length of the radio waves electrically. If you were to stretch the coil out with the antenna whip, it would be 9 feet long.

When the antenna does not match the wave length, part of the RF energy does not leave the antenna, and goes back down the feed line(coax) and hits the transmit transistor. Prolonged reflection to the transmit transistor, otherwise known as the final will blow it out. As well depending on how bad the length was off, the more off, the more reflect energy, the more RF energy you are blasting back into the radio, and this causes more things then just the transmit to blow out. Some time the receive goes along with it when it finally goes.

So if the RF gain is up all the way, which by the way is basically how much receive you have, and there really is no reason to have it down at all, and the CB/PA switch is on CB and the needle does not swing forward when its on the S/RF setting, chances are that the radio is now no good.

It is fixable, but if there are no CB shops near you then you will have to send it out. And Cobra will not cover this under warranty because its stated in their warranty that they do not cover damage due to high SWR.

Posted on Apr 06, 2010

audio20
  • 22 Answers

SOURCE: swr meter not moving.

If the radio is working don't worry about the meter unless you absolutely want it. These little meters are not very accurate or reliable. Get an external SWR meter to check the antenna.

Posted on Apr 23, 2009

wyoed1
  • 211 Answers

SOURCE: cobra 29 ltd modulation problen

You need to check the modulation on a modulation meter. Just because the meter doesn't peg, doesn't mean the modulation isn't working. Usally a meter pegging, means the swr's are too high or the meter is misadjusted. If in fact the modulation is low, their is a pot inside the radio (VR4) that will add gain to the modulation circuit. This setting is legally supose to be set by a qualified technician.
Good Luck
Ed Meshechek ( Radio Man )
NC Electronics
PO Box 1696
414 6th St.
Mills, Wyoming
82644
307-266-4675
wyoed1@aol.com

Posted on Dec 03, 2008

  • 200 Answers

SOURCE: cobra 29 nw ltd won't transmit

Have you cracked the radio open yet?  check for loose connections etc.  get back to me if that doesnt yeild any results

Posted on Jan 22, 2009

  • 773 Answers

SOURCE: cobra 29 ltd classic cb not transmitting

Check the ground. Make sure its grounded well on bare metal. To see if the ground is bad, or not making good connection, disconnect the antenna and turn it on. if it does not power up, that means your ground is bad, and it was grounding only through the antenna.

Make sure not to key up with out the antenna connected.

Posted on Feb 08, 2009

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1 Answer

Cobra 29 ltd classic year 2004. rf gain problems.


Put SWR meter between your antenna and output, test wave length receive/transmit, might need a ground plane or center loaded stick.
Could be transceiver relay, try clicking mic fast, it should click out as fast as you key the mic.

Oct 26, 2016 | Cobra Radio Communications

1 Answer

Problem no squelch noise or speaker like its muted, but can hear weather ok shows receiving and ant ok


Since the radio cannot transmit on Weather bands, there is no need for the radio to detect if it is transmitting when receiving weather.
In CB mode (on CB channels) the radio will mute when transmitting. So... a guess is that it is muting, or transmitting all the time in CB mode. Check for a mic problem by removing the Mic from the radio ... if it receives CB with no mic connected, then there is an issue with the mic. Otherwise, unless the unit is in PA mode (public address mode) it is likely something internal and beyond the scope of this service.

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1 Answer

How to fix cobra 29 lx that will receive but not transmit?


your final could be blown,thus no transmit . if you change it make sure you change the driver also and retune that portion of the radio.

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1 Answer

Transmits but does not receive. cobra29LTD Can it be a active copponent


where is the RF gain? It should be all the way up.

The other thing that can cause no receive. Its a common issue. If you have a mic with a broken wire in cord, if its the wire for receive, then when the key is released the radio will not go into receive mode. The switch in the mic determines weather the radio is in transmit mode or receive mode.

So make sure the RF gain is on max, and try another mic.

Sep 26, 2010 | Cobra 29 LTD CB Radio

1 Answer

I have a cobra power mic that has no audio output


Sounds like its not wired up right, the audio wire must be off,take the plug apart and check the white wire, re-solder it. here is the wiring, pin1-shield,pin-2audio-(white), pin3-transmit-(red), pin4-receive-(black).....hope this was helpful...

Apr 23, 2010 | Cobra 29 LTD CB Radio

2 Answers

When i click the mic i get no transmit


If the receive works ok,sounds like a mic
problem,try another mic if you can find a
buddy who has a Cobra that may let you
try it most all Cobra mic will work but not all.
Good Luck

Sep 08, 2009 | Cobra 29 LTD CB Radio

1 Answer

No squelch


Yep that should happen.
Green or no color in receive mode
Red when you key the mic to let you know when you are transmiting

Feb 28, 2009 | Cobra 29 LTD CB Radio

1 Answer

I have a cobra 29 and all it will do is light up. It will not receive nor will it transmit. What might be the problem?


the easiest thing to check first is the mic..........if the mic is broken cobras wont receive or transmit
hope this helps.......good luck!

Dec 05, 2008 | Cobra 25 LTD 40-Channels Base CB Radio

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