Questions About 2 Cobra 29's I Uicked Up

[RBeach]

Hello all! New to the forum, and somewhat new to CB's. I have owned several in the past, mainly for hunting and listening to on the road, but wanted to step back in.

The first I picked up was a Cobra 29 WXNWST. He said it was peak and tuned. But, from the research I have been doing, he had the cheap way out, and had D11 cut. Not sure what else was done to it.

The other is a Cobra 29 LTD Classic (front mic), that he said was also peak and tuned, but D11 was not clipped.

Is there anything else on these boards I need to look for being clipped or removed, or added? I haven't mounted them in the vehicle yet. Still need a mounting bracket, and the universals won't work with the big bolts for adjusting width. Need to check online for the bracket I guess. The only local CB shop shut down 2 weeks ago due to his place getting robbed.

I currently have an el cheapo Maxon MCB-45W int here now. My SWR is around 1.5, maybe a hair lower. The Maxon had a peak and tune a while back, and then I made a mod to it. Just looking to step up a notch.

Also, the Cobra 29 LTD Classic:

When I put the SWR switch on CAL to calibrate it, the needle just fluctuates wildly as I try to set teh calibration.

What would cause this?

 

[Robb]

I suspect that the mic may be causing the wild fluctuations when trying to calibrate the SWR. It may well have a broken wire in the plug itself. Don't be surprised - it happens quite often. Does this same thing happen with the other radios as well?

As far as D11 is concerned, if it is still on the board you can always re-solder it back together. There are better mods for modularion improvement on the 29 than clipping the limiter diode. Use the search feature to find all posts about the Cobra 29 - you will find some decent stuff here.

Wecome to the forum.

 

[RBeach]

Yeah. It is a new Cobra M73 mic. I tested it out on another radio and the SWR and calibration works perfectly (I got 2 used 29's the other day). Started with just a basic mic to begin with.

The weather has been bad here all day, and I am not sure if that is hampering my ability to get out. Even on the el cheapo Maxon I have in there now (which has been peaked and tuned), it is not picking up much of anything, and no one is responding on it either. One of those days, I guess.

 

[Robb]

If all of the radios are acting in a like fashion; I would stop transmitting until the fault is found. Most likely, it sounds like a bad cable or imperfect connection on the antenna or a coax connector. Are you still hearing local stations/friends? Or are they intermittant?

If the radio sees a 'no load' situation - all of the output power from the final output transistors will be reflected back into them - and subsequent failure can be imminent. I say this because if ALL of the radios are seeing intermittant SWR readings; then there MUST be an open or short somewhere between the radio and antenna. Including the coax and connectors. The wind may have opened up a connection somewhere - so be careful. Even a cheap radio can cost more $$$ to fix than they are worth...

 

[RBeach]

If all of the radios are acting in a like fashion; I would stop transmitting until the fault is found. Most likely, it sounds like a bad cable or imperfect connection on the antenna or a coax connector. Are you still hearing local stations/friends? Or are they intermittant?

Everything was working perfectly earlier in the day. Strong clear signals on the interstate. I connected back to the Maxon I had in the vehicle, but there wasn't much chatter. Like I said, we were having some bad storms here, so that could have played a factor. The weather stations on the 29WXNWST was coming in crystal clear. Other than that, not much. Plus, my house is kind of out of the way of the interstate. I didn't hear much on 6 or 11 tonight that I can recall. Earlier in the day I did though.

I am going to go back out tomorrow and check it out.

As for the coax connectors, I actually had to resolder new ends on about a week ago, because the old ones had broken loose (bad solder joints by the person who made it). Made a HUGE improvement over what it was before.

As for the antenna, I think I may go mag mount on the roof, but trying to decide on which one and the height. Height is kind of a limiting factor without having to remove it all the time (I park in a parking deck at work). Was think a Wilson mag mount with the 39" whip. Currently using a 3' Wilson fiberglass mounted in the right rear door frame, getting about a 1.5 SWR throughout.

 

[Moleculo]

RBeach: welcome to the forum

When you check the SWR, did you turn the mic gain down? If not, you should. If the SWR fluctuates all over the place, then you have a bad coax connection someplace or an issue with your antenna or mount. You'll want to make sure and find it before using your new radios.

 

[RBeach]

RBeach: welcome to the forum

When you check the SWR, did you turn the mic gain down? If not, you should. If the SWR fluctuates all over the place, then you have a bad coax connection someplace or an issue with your antenna or mount. You'll want to make sure and find it before using your new radios.

The SWR only fluctuates on the 29 LTD Classic.

It does not do it on my seperate meter, nor on the 29 WXNWST.

Yes. I turned the mic gain all the way down.

 

[Big Dummy 123]

HI the swr cal pot may be dirty.

 

[Radio Tech]

HI the swr cal pot may be dirty.

My first guess also

 

[RBeach]

I have some electrical contact cleaner. I am going to see if I can clean it tonight, and see where that gets me.