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Old 06-12-2011, 2:41 PM
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Default Cobra 29LX Antenna warning light

Cobra 29LX Antenna warning light Problem
I noticed on my second 29LX the problem of an antenna warning light coming on seems to happen and apparently happens on all the 29LXs. It seems like all radio test pass SWR 1.3 to 1, Battery Test Passes, and Power Test Passes, but the warning light still comes on even as you talk. It will come on and off in the middle of a transmission. I know Cobra gives instruction on how to re adjust the warning light sensitivity but why should it be changed? Is this really saying something is wrong or what? Input wanted Ron
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Old 06-13-2011, 3:52 PM
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Lets look at it like this.

If you do not have a SWR meter and your only guess is what the radio tell you and the radio is trying to protect itself - and with most new vehicles being half or more plastic - then you are going to have a high SWR - especially if you do not have the antenna mounted in the proper place - the middle of the roof with a good ground - hole drilled through the roof - and the proper antenna cable going from the radio to the antenna.

Do a internet search and find line impedance's for cable.
Then look up and find what a Smith Chart is.
Then get someone to explain to you how the Smith Chart works.
You might then be able to determine the proper length for the cable that came with the antenna that you bought and figure out the best way to get the line impedance down to a more manageable level.

The bottom line is - most people do not know how to install a cb radio properly and that is the reason why most people should take their cb radio to a real cb radio shop and have it installed professionally.

If you buy your cb off the cb shop and they install it improperly and it burns up then shouldn't they have to pay to fix or replace it?
Sounds like a real cheap insurance policy to me.
If they install it and the light comes on - then you take it back and make them do it again until it is right.

Taking a used cb to a cb shop and asking them to correct your mistakes would be like me talking a bologna sandwich to a restaurant and ordering a glass of water.
I think that is what the problem is - if a cb shop didn't sell it - they don't want to be bothered with it.
At the same time - just because a person had a 1/2 watt walkie talkie when they were a kid and it didn't need any special attention to make it work - other then a 9 volt battery, most people thinks that putting a cb radio into a vehicle is like putting in a car stereo where all you have to do is connect the wires to the power and ground and hook up the antenna and it will work.
Only it doesn't work that way.
Mainly because a receiver only receives and it doesn't care where the antenna is put or how long it is.
All it cares about is that you give it the proper amount of power to make the lights come on.

CB's are a transceiver - which means it both listens and transmits.
Any transmitter be it a CB or a television station all works on the same principal and when you try to bend the laws of physic's - you usually aren't successful.
It takes a antenna of a certain shape and size and location with a good ground plane and a certain type of conductor to transfer the signal from the radio to the antenna.
Even with that, there are all sorts of transceivers out there and they are not all the same.
If they were - then they would have a hard time selling someone a $400 CB radio when you can go to Radio Shack and buy a cheap Uniden for under $40.00
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Old 06-13-2011, 4:51 PM
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Now here is another tech question. The CB is connected to + and -. The - is the ground. After checking I find the antenna cable is connected to the case of the CB and all screws in the outside on the case are connected to the ground side of the antenna cable. Why isn't the case grounded to the vehicle if the set is connected to the ground negative at the power connector? Cobra says to ground the case if its not on the bracket which should be grounded or screwed into the car body or ground. Would this make a difference with the antenna? Ron
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Old 07-20-2012, 6:13 PM
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i am having the same problem with my Cobra 29 LTD Classic, standing wavwe is exelent but still get an antenna light
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Old 07-21-2012, 5:38 AM
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Can you exchange radio? Call cobra to ask how to reduce sensitivity of antenna light. what is the SWR? Ron
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Originally Posted by birddog56 View Post
i am having the same problem with my Cobra 29 LTD Classic, standing wavwe is exelent but still get an antenna light
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Old 07-21-2012, 6:08 AM
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Check your antenna ground make sure that the antenna is grounded good,if you are using a mag mount some time these antennas don't make good ground this will cause the light to come on at times,and if not make sure that your antenna is grounded very well,1.3 swr is not that bad but i would try to get it a little lower if you can and use a swr meter to check your swr's and don't depend on a light on the radio if you don't have an swr meter buy or find one and tune the antenna to get the best swr's you can get hope this help you out 73's..............
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Old 07-21-2012, 10:32 AM
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the cobra 29 has built in meter that i used, i have always used the radio meter to set standing wave and have never ad any trouble til now, took ariginal radio back and swaped it or new one. when checking the standing wave the needle barley move how eve when i talk the antenna light comes on
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