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Found a cobra 29 ltd classic at a yard sale for 20 bucks no antenna plugged up to my power supply 13.8 volt 7amp surge 5amp constant powers on but no squelch did not try to key up no antenna will i need one before i get any sound

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  • Master
  • 1,162 Answers

Any standard CB antenna an cable go to Radio Shack.

Posted on Mar 26, 2014

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Posted on Jan 02, 2017

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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

Laron71
  • 146 Answers

SOURCE: how to match a antenna to a cobra 29 LTD Classic

You are actually tuning the antenna to the vehicle it is mounted on here are some very good resources. http://www.rightchannelradios.com/pages/cb-antenna-tuning-guide-pv-c0-61.htmlhttp://www.wilsonantenna.com/swr.php

Be aware that if your radio has been modified it may produce a dirt signal that an swr meter may read as reflected power. In this case it may be more accurate set with a unmodified radio also if your radio is setup for a linear it may have a deadkey to low for the swr meter to calibrate correctly.
Hope this was of help.

Posted on Nov 28, 2011

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I disconnected and reconnected the cobra 29 nw ltd classic and now my voice is heard very low and slow it was working fine just before disconnection. can you help


How did you disconnect it?? Antenna wire?? Power supply?? Microphone?? May be that you have a short in your coax in back of radio. Try taking it loose and screw it back in. Try new coax. Turn up Mic gain knob or change microphone. Make sure power wires are connected RED to RED(+) and Black to Black(-). Try grounding radio to metal ; if inside house ground to metal water pipes, filing cabinet, breaker box or meter box or 8 foot rod into earth. Measure SWR it should read 1.1 to 1.5. Measure power supply with Voltmeter it should be 12 to 15 volts. Check antenna plug in back of radio is my guess or microphone itself.

May 09, 2011 | Cobra 29 LTD CB Radio

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I found an old cobra trapshooter 3120, how do I set it up?


hello firstly you will need an antenna 27mhz a swr metre to match the antenna to the radio and a constant 13.8v power supply

Jan 05, 2011 | Cobra 29 LTD CB Radio

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red wire 12 volt all time conected to power supply and orenge wire 12volt when is on and 0 volt when is off ,this wired are in on off switch.

Mar 25, 2009 | Cobra 29 LTD CB Radio

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The wires should just attach to the red and black terminals on the radio, strip some wire unscrew the terminals a little wrap behind, and tighten again. Good luck! Or buy some banana plugs and they will plug right in the front

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Cobra 29 nw ltd classic


Hello candy_72_99,

Hello candy_72_99,

If I am correct what you are saying is that your radio has poor modulation? ok. First I need you to run two tests for me.

1) Power output Test: connect a power meter to the antenna jack and the other connector of the meter to the antenna, Key up the mic and record the power reading is should be 4W PEP or 36.02dbm

2) Then I want you to take an oscilloscope and put a 1khz tone in to the mic while measuring the RF output at 100% modulation the wave form should not clip.

If these two test are good then your modulation is ok. What I believe you are asking for is more power or better power efficiency.

Try to tune your antenna for 1:1.0 or 1:1.2 SWR with a SWR meter this should deliver the full power to your antenna.

I hope this helps

Thank you,

Shuttle83

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Shorts my power supply when plugged in


do you have boots powering up the signal that can do it

Sep 27, 2008 | Cobra 29 LTD CB Radio

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Cobra 29 Ltd


Hi,

Appreciate the direct "Ask Me" again.

The initial posting would still hold true, best would be:
  • remove TR18;
  • replace 2SC2069 with 2SC1969; and
  • adjust L12, 13 & 14.
Hope this be of initial help/idea. Pls post back how things turned up or should you need additional information.

Good luck and kind regards. Thank you for using FixYa.

Sep 07, 2008 | Cobra 29 LTD CB Radio

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