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Cobra 29wx cb radio not transmitting.

ZooMad75

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Ok, so as the title says my cobra 29wx radio does not want to play nice with me. No transmission or reception. Funny thing is the anteanna and cable are new. I was able to get the SWR dialed in yesterday and had it down to 1.5 on 1 and 40. Pretty good I thought. I even used the the swr feature on the radio and got a similar reading. I tried it out and didn't hear much traffic on 19, but then again I'm not right on the interstate where I'm at either. The weather radio feature works, so does the PA. When I key up the mic the needle moves on the meter and the led changes from green to red.

So I did that yesterday. My buddy with the Jeep needed me to re-tune his cb since he added a spring to his antenna. He came over today and I dialed his in pretty quickly and since he was there, fired up mine to check them both. Funny thing, now mine won't move the needle at all. We can hear me key up the mic by a click on his radio, but nothing comes across. He tries talking to me and still nothing. I went back and hooked up my SWR meter and checking again I have no movement on my SWR meter. I even went and grabbed an extra cable I had and hooked it up. No difference.

I'm trying to figure out what the hell I did. I'm afraid the radio took a dump.

Fellow CB radio guys? Any thoughts?
 

Bent77

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I went through this recently too. Was still the cable. The primary (inner core) was intact, but the ground wire section had come loose from the coaxial end inside the wire.

I did think it was the radio for a long time. Even bought new antenna and CB
 

Bent77

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The metal collars on each end should have continuity to itself. The core of the coaxial to itself also. I can go see what ohm numbers the new cable I have reads if you want
 

ZooMad75

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The cable I used had a two part end to allow running through the body with a smaller hole. I noticed yesterday when I disconnected the cable from the radio to hook up the swr meter, the normal end wasn't tight to the small end. I tightened it and was able to get readings and have the needle move on my radio. I checked that again today and it's tight. I guess I need to break out my DVOM.
 

Bent77

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The cable I used had a two part end to allow running through the body with a smaller hole. I noticed yesterday when I disconnected the cable from the radio to hook up the swr meter, the normal end wasn't tight to the small end. I tightened it and was able to get readings and have the needle move on my radio. I checked that again today and it's tight. I guess I need to break out my DVOM.
That's about how mine went. I'll pull some numbers off the known good and known bad cables I have
 

Bent77

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So...
Good .3 Ohm on the core
.3 Ohm on the "ground"

Known bad
.3 ohm on the core
.3-11.5 to OL (depending how I move it) on the ground

Both readings on a Fluke 117
 

ZooMad75

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I'll check those tomorrow. Not sure if I have enough length on my leads to reach the back corner and the console. I'll find out.
 

Bent77

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I'll check those tomorrow. Not sure if I have enough length on my leads to reach the back corner and the console. I'll find out.
Yeah, i pulled the end off the antenna to check. Darn shame im not closer to you, be happy to let you use what i have to swap n check.
Paid $23 for the new cable. Seems inexpensive compared to a cb though...
 

ZooMad75

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I appreciate the offer. I've got a good dvom to use, I'll just need to elist my wife to hold one lead on one end and then I'll get the other. It's just odd the other cable I tried behaved the same way. Trust me I don't want to replace the cb if I don't have too. It's a pain in the ass to pull out of the console.
 

Bent77

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It's more I'm hoping that's the culprit...
 

ZooMad75

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I spent the afternoon Screwing around with the CB headache. Checked resistance, less than .3ohm on the core and on the gound. Checked my continuity to ground on the antenna mount and had none. I had painted the antenna mount and didn't use any star washers on it. So I pulled it apart and wire wheeled the paint off where the mount bolts to the body inside the jamb and where the aluminum mount goes to the steel mount. Rechecked continuity at the mount, now it's good. Went inside and rewired the power and ground for the radio itself. Figured the ground being put on the mount to the console might not have been solid enough since it bolted down to the raptor lined floor. I took and ran the ground up to one of the bolts that hold the t-case shifter mount to the floor. I rechecked the continuity to ground at the radio end of the cable to the same point the radio was grouned to, came up .000. Figured I got it now.

Nope. I powered it up, keyed up the mic and not a twitch on the meter. PA and Weather radio works, but no transmit/recieve. I'm about convinced at this point my radio shot craps.
 

Bent77

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Well that just sucks
 

ZooMad75

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I'm going to break out an old radio I have tomorrow and set it up to try it out. If I can get it to work on this antenna I'll know it's the radio.
 

diesel4me

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I've had mike problems prevent a CB from keying up--one of the three or four wires on the plug had chafed inside and touched the braid on the sheathing..

I think most CB's have a relay the mike button activates to put it in transmit mode,then back to listen when the button is released..that could be faulty,if the mike is sending power to activate it..

Some CB's have pretty fragile output transistors or some type of protection device that prevents it from frying the outputs that can fail,if it gets keyed up with no antenna load..
I'm no CB service man,but I know guys who had their outputs or that device fail and all they had was "receive" ,no trasmit ability..had to bring the radio to a shop,in one case another new CB was less than the repair would have been...the Cobra 29wx sounds like a "classic" metal cased unit,not one of the newer tiny ones ?..

You can make a "dummy load" from a light bulb to see if its the radio or the antenna at fault..I think a #47 bulb was the correct number to use...or resistors as shown below..I posted a photo of the bulb type somewhere here before on CK5,either this forum,or maybe the "Garage"--cant find the photo in my saved photos.. DummyLoad.jpg
 

ZooMad75

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Thanks for the input both of you. I don't have an extra coax connector to pull from to make the dummy load. So I broke out an old radio that my Grandpa installed in his 1976 Caprice when he bought it new He had it set up to work on a 12v outlet so I plugged it in and hooked the swr meter and antenna cable. I got nearly identical SWR values as the Cobra did when I was able to tune it. Using a handheld cb my buddy loaned me I dialed up the same channel on both and keyed up the mic on the handheld. Along with some squelch from having the radios so close, my voice came over the old cb loud and clear. I could see the meter on the old radio move as it received the signal from the other radio. Going the other way I keyed up the mic on the old radio, the meter moved. I could hear a click on the handheld but my voice didn't come through. I then plugged in my pa speaker to the old radio just to check the mic. Same thing, it keys up and clicks but no voice. Pretty sure the mic is on the fritz.

But in my own completely unorthodox way I think I've came to the conclusion the Cobra is busted. I might see if anybody close can fix it and if the price to fix is less than a new radio I'll keep it. if not, time to go shopping.
 

ZooMad75

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Here's the test radio. When is the last time you saw a GE CB radio? Last time that SWR meter and radio were hooked together my Grandpa did it.


Took the Cobra out of the console if I can find somebody that can repair it.

 

Bent77

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If not, I have an extra CB I need to sell
 
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