Question about Cobra 25 LTD 40-Channels Base CB Radio

1 Answer

Turn on cobra 29 and it makes a constant feed back noise

Posted by Anonymous on

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  • Cobra Master
  • 1,795 Answers

Remove the mic and see if it still happens.try another mic and see if it still happens. Is this a new radio?If not someone may have wired it up wrong from the radio side of the plug. Go to www.cbtricks.com and check out the wireing schematic.

Posted on Sep 01, 2014

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Posted on Jan 02, 2017

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

Benimur
  • 6966 Answers

SOURCE: no receive cobra 29 ltd classic

Hi and welcome to FixYa,

Initially, pls confirm that there is modulation (transmit audio). The reason I asked is if IC4 (TA7222P) is blown, then the radio would have no audio amplifier which would explain no receive audio. Additionally, the final and pre-final (TR15 & 15) gets is modulated TX+12 through D8 from T1 which in turn is the output of IC4 through C48.

Perhaps a schematic diagram may be of further help.

Good luck and Thank you for using FixYa. Happy Holidays.

Posted on Dec 18, 2008

  • 773 Answers

SOURCE: cobra 29 ltd classic antenna calibration ??

Wow. That's not at all a solution to what this guy is asking. And why all the caps??

The one point jm77437 has that is correct is that you do not set the radio, you set the antenna. The rest is blah blah.

Here is how you tune your antenna for you radio. First off it depends on what kind of antenna you have. most fiberglass antennas have a tunable tip to adjust the height of the antenna. Metal whips either have a collar at the base that the whip will either slide up or down in to adjust the height. The other type of metal whip's you have to physically clip to shorten the antenna, you must be careful with this type because once its clipped, that's it. You cannot add what you cut off.

I am going to give this example using a metal whip with an adjustable collar.

First after your radio is hooked up in the vehicle, drive to an open lot. Buildings and other structures can cause extra reflection. turn to channel 1. Flip the meter to CAL. Key the mic without talking. Now turn the CAL knob up until the needle reaches the little upside down triangle all the way to the right marked CAL. Now you have just celebrated your radio for your setup to measure you SWR. Now while still holding the key, flip the meter switch to SWR. The needle will move, and where it stops is your SWR reading. The lower the better. Anything under 1.5 is considered really good. But still, the lower the better.

Make note of what your SWR was on ch 1.

Now flip to channel 40. Repeat the SWR process. You must recalabrate each time you take a reading.

Now like jm77437 said. If your SWR reading is higher on 40 then 1, then your antenna is too long, and you must make it shorter. Loosen the collar and lower the antenna in the collar 1/4 inch at a time. check the swr each time you adjust the antenna.

If your SWR reading is higher on channel 1, then your antenna is too short. You must make your antenna longer. Do this by loossening the collar and pulling the antenna upward in the collar 1/4 inch at a time, again checking the swr each time you adjust the antenna.

What you want to achieve is having the same SWR reading on channel 1 and 40. then you have the best match you are going to get with that antenna.

If your swr is under 1.5 on all channels, you don't need to fuss unless you are a perfectionist. then by all means go ahead.

If your reading is higher then 3, or your ant light comes on, something is really wrong. Make sure your antenna is connected all the way, and the coax is not damaged.

Its important to have an appropriate SWR because if you do not, you are reflecting too much signal back into the radio, and eventually you will burn out your final transistor, and your radio will be toast.

Some tips: make sure you check the swr with the doors and windows shut. Make sure you are in an open lot. Remember to calabrate ecah time you take a reading. If you have had your radio peaked by a radio shop, and they have lowered your dead key, or have done a swing modification, then the meter in your radio will not work when taking an SWR reading and you will have to use an external meter.

Posted on Apr 24, 2009

  • 773 Answers

SOURCE: cobra 29 ltd classic antenna calibration ??

You should not calibrate the antenna before you install it on the car!! the antenna needs to be calibrated on the vehicle that it is going to be on. Type of vehicle, different mounts, and many other variables can change the amount of reflection you will get.

j0hn9999 did a much better job but left some info out.

Take your SWR readings on channel 1, then on channel 40.... NOW, if your SWR is higher on ch 40 then ch 1, then your antenna is too long and it needs to be shortened. Refer to the antenna instructions on how to shorten the antenna.

If your SWR is higher on ch 1 then on ch 40 then your antenna is too short. You must lengthen the antenna. Again refer to your antenna instructions on how to lengthen your antenna.

You must calibrate each time you take a reading.

Make sure your doors and windows are shut when taking a reading

Make sure you are in an open lot when taking a reading as buildings, trees and other structures can cause reflection and give you an inaccurate reading.

If you adjust the length of your antenna on another vehicle and then put it on yours, the SWR will be off. It will need to be tuned again.

An external meter is better then the one in the radio, but will need to be hooked up in the vehicle you have the antenna on.

If you are not running any kind of power, or do not have a swing kit installed, and the radio is stock, the meter in the radio is more then enough to get a correct SWR reading.

Posted on Apr 24, 2009

  • 89 Answers

SOURCE: Receives but does not transmit. It is a Cobra 29

There are a few different things that can cause this problem. 1: If it is a power microphone (a microphone that requires a battery). Try replacing the battery. 2: Broken wires that go from the microphone to the plug that plugs into the radio.You can try gently taking the plug apart and inspecting the wires. If only one has come loose, you can re solder it to the pin it came from. If more than one has come loose, find a wiring schematic for the radio that tells which wire goes to which pin and re solder appropriately. 3:Have the SWR's checked on the antenna. If the SWR's are to high and the radio has been being used in this fashion, it could have burned up the transmit finals in the radio. If this is the case, you will need to take it to a reputable radio repair facility to have fixed.

Posted on Nov 30, 2009

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1 Answer

Cant adjust swr on cobra 29 with swing kit


make sure you have no noise in the background at all the be my guest. you may have to put a cloth over the mic speaker to keep the noise level down but you can do it.

Jan 28, 2014 | Cobra 29 LTD CB Radio

1 Answer

What is a voic box on a cobra 29 ltd? What is a good antt combo four a 29 ltd?


Cobra's LTD 29 model Citizen's Band radio features the full 40 channels allowed and a heavy-duty microphone. The radio provides 4 watts of AM radio frequency output with a switchable automatic noise limiter and noise blanker. Other features include Cobra's Delta-Tune function. Making a Cobra LTD 29 hear and receive better involves making changes to the radio's settings, including the settings specific to this brand.
M/F Turn the switch labeled "NB/ANL, ANL, OFF" to the "ANL" position and try the transmission again if noise is affecting reception. "ANL" is an automatic noise limiter function and reduces noise caused by the vehicle's electrical systems and electronics.

M/F Switch to "NB/ANL" to activate the noise blanker, which may also reduce noise if you continue to have problems. It's an RF noise filtration function and will help with ignition noise.

M/F Adjust the "RF Gain" knob by turning it clockwise to increase gain in weak signal areas if you have problems hearing radio traffic.

M/F Set the "Delta-Tune" function to capture a more listenable signal and get rid of adjacent channel noise. Rotate the knob labeled "Deltatune" to the center position for best tuning. Try micro-adjustments to the left or right as well.

M/F Turn the volume up if you still can't hear and as with any CB radio, adjust the squelch if the radio is noisy when there's no traffic. Turn the knob labeled "Squelch" all the way to the left to receive all signals, including noise and turn the control clockwise until the background noise stops. You will be able to hear the strongest transmissions without having to listen to weak signals and noise.
The service manual can be found here

Jan 23, 2013 | Lands Phones

1 Answer

I have a cobra 29 with echo, tweeked and tune. I can transmit strong and I hear those who speak to me but I dont have any static like you do with a new radio. Is this something I need to worry about as Im...


Make sure the squelch is turned all the way to the left, the RF GAIN is turned all the way to the right. The cobra 29 has a very good noise blanker, Turn the ANL/NB switch to off, You will probably hear a Lot of static, As long as you have a good ground on the radio and antenna, and your SWR is 1.5 or lower, you need not worry about static.

Oct 05, 2012 | Cobra 29 LTD CB Radio

1 Answer

I have an echo mic on my 29. I can't use mic gain at all without it squeeling. Can barely here my talk back in this position.


re do the talkback. take out the resistor for the talkback. and put in the talkback that is a little outta phase and you won't get that constant feed back. make sure all the modulation limiters are not cut also.. A good shop would tune up and talk back a radio correctly for $10-$15 dollars. any more and they are ripping you off. I make sure my customers radios do not squeal before giving it back. that means i may have to try different values for the talk back to be right. so the customer can have the mic gain 100 % and it be ok...then the microphone mic adjustment can be set also.. let me know if you need help

Jan 30, 2011 | Cobra 29 LTD CB Radio

1 Answer

I have a cobra 29 ltd chrome and it making a lot of static noise while driving or idling. it transmits and recieves fine though


Hi, my name is John. Welcome to FixYa. Try running your power strait from the battery, that will bypass a lot of your noise. RED (+) ground (-) . Thanks for choosing FixYa....John

Nov 30, 2010 | Cobra 29 LTD CB Radio

1 Answer

I just bought a cobra 29 ltd, i hooked it up and calibrated it the way the manual said but when i turn it on and turn my squelch all the way to the left i barley hear it at all, and i have the volume all...


there may be a very low noise level. If the noise level is low you will hear almost nothing. You need to go on ch 19 and drive near a major interstate.

Key up and say, "Break one nine for a radio check" and a trucker will come back and tell you its working. If you hear him okay, then your radio is working fine.

Some days, background noise is heavier and lighter then others.

Oct 18, 2010 | Cobra 29 LTD CB Radio

1 Answer

When i start my truck my cobra 29 ltd makes lots of noise


Sounds like an antenna problem, could be a ground issue

Nov 22, 2009 | Cobra 29 LTD CB Radio

1 Answer

Cobra 25LTD classic


that is called feed back turn down your mic gain and it will stop squelling when close to others.

Sep 27, 2008 | Cobra 29 LTD CB Radio

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