How can I tell if coax has a break?

[Thomas]

Talking CB radio antenna. RG58 cable goes from radio to antenna. The antenna is a Wilson little wil. The antenna end of the cable has no access. It is on my car and maybe closing the door pinched it? It was working fine for years. Is there a surefire way to cut and splice it? The splice will then be on top of the car in all nasty weather. I also am not sure of current SWR but there has been no antenna movement. I no longer have an SWR meter, I fried it. A new lil will is about 60 bucks for a cheaper one.

[retired1]

If you have or can borrow a multimeter, disconnect cable from radio, pull it back near the antenna, and check for short or open.

Would not recommend a splice as it may distort waveform or signal strength.

Even if it means working with a solder joint at the antenna, best to replace entire cable.

Assuming it's a trunk mount, can you not run cable under the car to radio ?

Good Luck, and have fun ;-)

[invalid unparseable]

Thomas wrote on 3/4/2023 4:49 PM:

If your car door had pinched the cable then you should be able to see it.

Maybe your CB radio had blown a fuse. Can you see any indication that it is powered on?

[Thomas]

Antenna is on car top. CB works. I pick up the stronger signals but no tx that I get answers on. The cable has no visible damage other than it being bent where the car door closes on it. I would cut it and resolder in the mount but there is more action going on in the base for me to damage. My dilemma is I can buy a new antenna but then need it swr tuned. I have a multimeter but do not understand the first suggestion. The base end is sealed. "Pull it back near the antenna"? The coax is maybe 15 feet.

[micky]

You can be the judge if this will help.

Disconnect the antenna from the radio. On the far side of the possible break use a hat pin** to pierce the cable. The shielding won't have broken, only the center wire, right? But still first check the braid and then aim the hat pin for the center wire and measure the resistance from the radio end of the center wire to the pin. Keep probing until you hit the center wire. I've used pins and I may have once used it for coax. **a longer than average pin with a knob on top. Corsage pins are almost as good. Straight pins will work of course but are harder to use.

[invalid unparseable]

I don't think you can hear any CB traffic if your coax cable is broken. If you don't get replies on your tx, then the tx stage of your CB circuit board might be fried, or your mike is wonky, or nobody bothers to reply to your tx.

[retired1]

The center conductor of the coax is directly connected to the antenna itself, by way of the loading coil in the base.

So clip one meter lead to center pin on radio end and, other lead to antenna (assuming the metal antenna is not covered with plastic or something)

[Thomas]

Excellent. Learned something new. I did like Micky's out of the box thinking before I understood the path. Weather permitting I will test tomorrow and reply. So, if open, can I splice? I don't really think the cb is bad.

[retired1]

If you have never spliced coax before, it is not a simple process. Usually needs special tools, but can be done with wire cutters and knife if very careful.

Take a look here:

[invalid unparseable]

I don't think his car door pinching can break the core wire in a coaxial cable. The core wire should have high copper content and you need to deliberately bend the cable at sharp angle numerous times before the core wire would break.

[rbowman]

Micky's 'out of the box thinking' is the traditional way to screw with a neighborhood ham who is interfering with other signals, assuming you can get to his antenna feed some dark night.

[Thomas]

I have a backup cb in another car to swap out. Pita but doable. I will do the coax test first, i hope it is good. If so, the swap will tell. Everything is about 15 years old.

[invalid unparseable]

Why don't you park the two cars side by side and then transmit on this one to see if you can hear yourself on the other one? I'd bet my money on your mike not working. If you cannot hear yourself, pull the mike from the other car and try again.

[Thomas]

My mike is not preventing reception. Should know in a few hours after some jobs to do. Thanks for the suggestions.

[TimR]

The way to test coax is TDR, time domain reflectometry. (I said that authoritatively as if I'm an expert. I did this once in 1986 and there may be something better now.) It's a gadget that sends a signal down the line and checks for the reflection. An open gives one kind, a short another, other faults give you other results, and the amount of time shows you exactly where.

Of course you don't buy one, you borrow one from a ham or a school.

[Thomas]

Everything tested ok. I brought it inside to test. Bummer. I took it apart and replaced the coax and resoldered it all. Added new sealant (I used plumbers putty) no go. Time for new. I do not know enough about the inner diodes hidden in shrink wrap. Opening that wrap was going to break whatever was inside so I hoped to get lucky.

[Thomas]

Ok, this officially sucks. New Wilson little wil antenna, same as the old.

2 cb's, an mcb 30, the old, and a new president adams II. The adams has a built in weather radio. I opted for this to get rid of my police scanner in the car. Local police no longer transmit where I am at. (Hanover twp Pa 18706). The weather station is fine on the new adams. The tx/rx sucks all the way. I think the only thing I hear is skip from where you are, be it NJ or OH. Install polarity is correct. No swr meter until Saturday. I moved the stinger in up/down small increments with no change at all. Notta. I swapped the old one in. It was cut about an inch or better up against the new. Up/down, no change at all. The "skip" cancels when I touch the old or new. I cannot fathom that this new rig gets no reception or tx at all. This is on a nissan suv murano, same set up when it all worked. I am less than a mile from I81 straight line of vision and could hear the traffic on a quiet night ish. I have been using cb's for 40 years. What can I be overlooking? Gotta be something so simple I am going to punch myself when I figure it out. Bring on the crazy.

[Thomas]

Back in business but another question I cannot find a good answer to. I am tuned equal at 1.7 on Channel 1 and 40. On channel 19 where I want to be it falls to a perfect 1.0 Is it ok to be high on the ends and perfect where I am on ch 19? I was expecting across the board numbers. Is it explainable for the mid channels being better?

[Ralph Mowery]

That is normal. If you look at the resonate curve of an antenna the SWR will start off very high below the resonate frequency (where the antenna is too long) and start dropping as you reach the resonate frequency and then start back up (where the antenna is too short).

Anything below around 2:1 is usually fine.

[Thomas]

Thank you. I get to put the tools away. One last observation about this. I am transmitting better on 19 than 1 or 40 correct? That is my only goal.