Question about Cobra 29 WX NW ST 40-Channels Base CB Radio

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Cobra 29 voltage regulator - Cobra 29 WX NW ST 40-Channels Base CB Radio

Posted by Anonymous on

  • William Clayton
    William Clayton Feb 14, 2015

    Hi Anonymous, I want to help you with your question, but I need more information from you. Can you please add details in the comment box?

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6 Suggested Answers

6ya6ya
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Posted on Jan 02, 2017

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One Wire
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SOURCE: echo on cobra 29

When you purchase an echo board, the instructions come with them.

If you need any help, don't hesitate to email me at rollincbmods@yahoo.com

Dean Pitts
Rollin CBs

Posted on Aug 31, 2008

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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

  • 6 Answers

SOURCE: no transmit on cobra 29

Check your coaxe and the antena

Posted on Aug 30, 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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Hi,

Your concern is no transmit and no red transmit led -

If there is no receive likewise, then probably problem in the PLL/VCO section or 9V voltage regulator TR23 (2SC1096) or Zener diode D22 (9.1V).

If the receive is normal, then possibly any of two (2) faults:
1. microphone/PTT switch and/or the mic cable specifically the wire connected to pin# 3 of the connector; or
2. +8V switching transistor TR21 (2SA733P).

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.

Jun 30, 2008 | Cobra 29 LTD CB Radio

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