Question about Cobra 148 GTL 120-Channels Base CB Radio

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Low sound on incoming

I have little sound coming in turned all the way up in. & ext. have not checket out going yet . can a bad ant. line be the prob.?

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Re: low sound on incoming

Have you checked your squelch control? try turning it completly counter clockwise this should un-squelch your receiver and increase the sound, however this might also be a sign of poor reception which would indicate a bad anntena, poor grounding or coaxial cable. Check and or replace these items before continuing. If replacing these do not help your situation then the unit itself has a problem. I would suggest that you take it to a radio repair shop and get the work done by a professional, since there are not user serviceable parts in the device.

Posted on Sep 04, 2007

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When I turn my cobra 29wxst on, I hear chatter (ppl talking) for a split second then nothing. When i key up, nothing, no swing or anything. However, i get weather. All the basics are covered, coax, ant,...

You've probably already done this, but make sure all the basic settings are correct. CB-PA switch is in CB mode, Squelch is turned to the left, RF Gain is turned to the right, etc. After all that, and you still have nothing, I would try using another microphone. If you have a spare mic or a friend with a spare mic, borrow it. Just make sure its wired the same as yours is. (If it's a cobra 4-pin, it most likely will work.)
Now if that doesn't fix it, then the most likely problem is in the MIC/AUDIO circuit. You'll need someone with experience to replace the necessary parts.
In radio troubleshooting, always start with the basics:
Correct Connections
Proper input Voltage (Power)
Correct Settings (Vol, Sql, RF-G, etc)
Antenna (properly matched)
I hope this helps a little...

Mar 20, 2013 | CB Radios

1 Answer

My cobra 18 wx st comes on and goes tru all channels but has no noise at all coming thru it. none of the signal strength lights come on or anything. its brand new.

Sounds like a antenna issue. Make sure coax is in good order.and antenna is connected properly. You might have to get a "swr" meter to put in line between radio and antenna to make sure antenna is "tuned" to were the radio is operating. Radio shack sells a ok low budget swr/power meter.

Nov 09, 2012 | Cobra 18 WX ST 40-Channels Base CB Radio

1 Answer

When set my swr to the ant it is fine i turn off the radio turn back it dose not want work right after that

hi I to had that problem and it was all down to a bad connection on the coax line please check for short along coax line ,try and get the shortest run of coax to the antenna as possible if this fails try using another swr metre as your own could be given a false reading . goodluck

Jan 09, 2011 | 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

Fresh install SWR will not come down

have you checked the coax connectors? It's gotta be a bad connector,damaged coax or a defective antenna. Careful--don't test "too much" or you'll burnout the final amp!

Dec 27, 2008 | Connex 3300 240-Channels Base CB Radio

1 Answer

CB radio PA speaker

Freddy, hello. The first thought that comes to mind with your problem is that if the 29 is an older model, the audio circuit or audio chip could be tired. If your talking about the receive volume being low thru the ext. speaker, then there is a rx. wire inside the mic cord. When it breaks, it cuts the volume in about half. The rx. wire is on pin # 4. Maybe your using the wrong ohm value speaker. You need 4 or 8 ohm. If you are refering to the outgoing modulation being real low, then the radio mod. has just been turned down to 50-60%. That's about all I've got for now, not being able to actuallly see the radio,,, Have a good day, and let me know how it goes,, Mechanic

Oct 22, 2008 | CB Radios

2 Answers

Poor reception

Sounds as though You have a bad antenna system ( may be bad coax ). Unless there is infact something wrong with the radio ( this is unlikey) you need to have the SWR's ( Standing Wave Ratio ) checked and trouble shoot the antenna problem. Although the ST seems to be ( In my opion ) the worst recieve radio Cobra could develope, they normally work to a good standard. As for the meter not working, this may also be lack of a good signal from the ant problem. If infact the antenna and coax is good, then take a close look at the output ( final ) transistor. If it's shorted, it doesn't receive well nor does it transmit well.
Good Luck
NC Electronic
Mills, Wyoming

Nov 03, 2007 | Cobra 29 WX NW ST 40-Channels Base CB...

2 Answers

Terrible static

What type of antennae are you using? If you are using an aluminum or stainless steel ant, I would suggest switching ti a fiberglass ant. It sounds like the metal ant is picking up the ambient voltage from the lines. If you are using a fiberglass already let me know, as you may have a more serious problem. Good Luck and I hope this helpsd L8R

Sep 17, 2007 | Cobra 29 LTD CB Radio

1 Answer

Cobra 29GTL Won't Transmit

if the red ant light comes on this means that you have antenna trouble either in the antenna itself or the coax but this should not have anything to do with the radio not transmitting. it sounds to me that you have a bad audio chip or a bad power output transistor. in either case you should really take it to a cb shop and let the professionals solve your problem, good luck!!

Aug 16, 2007 | Cobra 148 GTL 120-Channels Base CB Radio

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