Question about Cobra 29 LTD CB Radio

4 Answers

Cobra 29 ANT light

I have a brand new Cobra 29 that was working just fine, new wire's, new antenna (wilson), hooked in a 100 watt Linear amp. tuned my swr's there all below 2 hi end and low end, I know how to do this I know this to be correct and working, but know while the amp is on or off the ANT light is coming on. The swr's are fine and all the wire is new and good so is the antenna, the question is, has any one else had this problem? is there a real problem here? or is this jus feedback off the amp?

Posted by johnx44 on

  • johnx44 Sep 09, 2007

    My SWR's are staying below 2 at all times, and the light comes on even if the amp is off. It was my understanding that the light should only come on it the swr is over 3 but its not. Thanks though man, hopefully its just an error.

  • Anonymous Mar 28, 2009

    have problems with my swr cant get it below 3 and have tryed 2 different antennas coax is brand new

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4 Answers

Anonymous

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I believe it to be feedback but be aware of your Standing wave ratio because using a linear amp radiates signal to the point that it could cause that light to come on. There is a problem if the radiated signal is feeding back into the amp a a higher level that it can withstand over time.

Posted on Sep 09, 2007

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die2end

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First off, how are you testing your swr? If you are using the meter on the radio chances are that it is wrong. Try to get you hands on an external meter and test for your swr. Try to get it as close to 1 as possible. It's really not hard to do. I am getting a 1.1:2 on my Pete. If your swr checks out fine with an external meter the problem is going to be in the radio and is a easy fix. Take the cover off of the radio, find the small pot labeled vr6 and with a plastic screwdriver, turn it counterclockwise just a hair. This is a common problem with the 29s. They are sometimes turned to far. Vr6 is used to adjust the sensitivity of the ant light. And when you get a peak&tune most good shops would turn this down.

Posted on Jan 18, 2012

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Hi, If I may add to the two other posts, where is the SWR warning LED lighting up, in your Cobra 29 of in your linear amp? 1. If in your Cobra 29, then it is the SWR of the input circuitry of the amp that is causing the warning led. It is also possible for the jumper coaxial cable or connectors between the Cobra and the amp to be causing this. As a reminder the coax should be rated at 50ohms (RG58 or 8), connectors should be PL-259s with reducer if using 58s. One way to check is to use a dummy load at the end of the jumper cable (using a double-female adapter) which should then give a reading of flat 1. If it were the amp's input circuitry, normally there are varicaps for that purpose inside the amp. 2. If it were the amp's SWR warning lighting up, it may be that the SWR of your Wilson antenna is registering a 2 reading if using only the Cobra (@ 5 watts) to measure but increases when the power output also increases (as the case maybe when pushing the 100 watts). Your best bet probably is to lower the 2 reading down further hopefully to 1.2 which is time consuming but not impossible. Of course SWR will vary also depending also on the frequency. Hope this be of additional help/idea. Post back how things turned up or should you need further information. Good luck and kind regards.

Posted on Sep 23, 2007

Anonymous

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Try using a balun between your amp and ant. Sounds like feed back coming back into your radio from the amp.

Posted on Sep 23, 2007

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