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I have a Cobra 29 LTD Classic Pro. Ser# W703339172 can not find Schematic. I replaced SWR meter and lost the Diode that goes between the power and ground.what size is it and where can i get just one?

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  • Cobra Master
  • 18,072 Answers

That diode is a 1N4003 and you can find them on mouser, ebay, digikey etc

Posted on Jul 26, 2019

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6 Suggested Answers

6ya6ya
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Posted on Jan 02, 2017

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  • 1 Answer

SOURCE: 29 help

hi, sounds like you have a problem with the SWR' S Probably too high. Tumbleweed01

Posted on Mar 16, 2008

Dodgem250
  • 68 Answers

SOURCE: Cobra 29 LTD Classic Operations Manual

For the operation manual, go to cobraelec.com or:

http://cobra.com/downloads/manuals/29LTDCLA.PDF


Thanks!
Dodgem

http://dodgem250.angelfire.com

Posted on May 10, 2008

Benimur
  • 6966 Answers

SOURCE: 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.

Posted on Sep 08, 2008

  • 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

  • 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

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High SWR on antenna system.. may have mess up your RF final transistors. if you were talking on it for a long time. have someone check the SWR on the antenna system... should be a FREE service.

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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.

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Calibrate For SWR (Standing Wave Ratio) http://www.cbtricks.com/radios/cobra/29ltd_bt/graphics/cobra_29ltd_bt_om.pdf
The CAL is only to calibrate meter for a swr check of you antenna system it does not calibrate radio.

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You insert an SWR meter in the antenna line, usually one end goes into the Antenna OUT socket, and the Antenna plugs into the SWR meter, you then tune you antenna coupler, inductor, & final PA, in the final stage, until you achieve a 1:1 SWR reading, this is however quite hard to achieve, so simply tune for the closest 1:1 SWR that you can achieve.

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The SWR meter connect between your antenna and your rig,
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Looking at the schematic TR23 colector ties in with
the power switch ,check D22 it's a 9.1 to 10 volt
zener diode also check C11 an D21.
TR23 shows to be a 2SC1096 I would go ahead and
replace it.Be sure that the CB-PA switch is in good
working order;
Good luck maybe this helped.

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29 help


hi, sounds like you have a problem with the SWR' S Probably too high. Tumbleweed01

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