Can I Generate a Signal for My Broken Cable with a Homemade TDR?

[John1397]

I have a 300 foot cable with multiple conductors one is broken what I want is an idea how to generate signal that could be picked up by am radio? Was thinking of trying a crt monitor with copper windings around the outside with one end tied to cable do not know if this would work or some way to construct a few components to generate a signal that can be picked up by portable radio either am or fm? Something cheap preferable.

John

 

[Averagesupernova]

Configure a small relay to buzz by tying the NC contacts in series with the coil. You have made a very small spark gap transmitter which will be picked up by an AM radio. You trying to locate the cable I assume?

 

[John1397]

I got those small relays from crt monitor circuit boards I do not if these would work they only have the coil + and - and switch circuit.

 

[berkeman]

I have a 300 foot cable with multiple conductors one is broken what I want is an idea how to generate signal that could be picked up by am radio? Was thinking of trying a crt monitor with copper windings around the outside with one end tied to cable do not know if this would work or some way to construct a few components to generate a signal that can be picked up by portable radio either am or fm? Something cheap preferable.

John

You shouldn't be broadcasting in the AM or FM bands, at least not with any power.

You can buy an FM Transmitter kit that meets the micropower requirements of the FCC, and up close, you probably would get enough signal coupled into the cable to be able to detect it. But if this is a multi-conductor cable, there will likely be enough cross-talk to make unique identification of the broken wire difficult.

Another option would be to get one of those AC Mains circuit tracer kits from the hardware store. They are made to trace wiring from a socket back to the breaker panel. You would need to modify the transmitter to work off of batteries instead of AC Mains, but otherwise it should give you what you want.

Can you say more about this cable? Is it only one that you need to debug/fix, or do you have to do this periodically on other cables too? There may be other ways to figure this out (like with a capacitance meter, etc.).

 

[John1397]

This wire has 16 conductors maybe to find one broken wire out of 16 this type of break detection will not work signal would have to be of the type that will not cross over from one wire to the other this probably not possible.

 

[dlgoff]

I'm thinking you need one of these:

http://www.flukenetworks.com/datacom-cabling/installation-tools/TS-100-Cable-Fault-Finder

 

[berkeman]

I'm thinking you need one of these:

http://www.flukenetworks.com/datacom-cabling/installation-tools/TS-100-Cable-Fault-Finder

Pretty handy! I didn't realize that they'd made TDRs so easy to use. A little pricey at $355, but still a good tool to know about.

 

[Windadct]

You can make a home made TDR - with a single pulse and a half decent scope - calibrate on the good wires in the cable. I had been thinking of the cable tracers - but TDR is much better idea in a multi-conductor cable.