Find Opposite End of Coax Cable Using Electric Field Probe

Thread Starter


Joined Apr 20, 2020

I'm trying to connect an additional set top cable box in another room of my house. There's a coax wall outlet already in the room, but it is not connected to the rest of my Verizon FiOS network. I'm having trouble finding the other end of this coax run to connect it to the rest of my network. If the opposite end happened to be unterminated (unconnected), it should in theory be capable of acting like an antenna and emitting an EM signal. I was thinking I may be able to drive the line with a signal, and then locate the other end using some sort of field probe. i.e. continuously 'sniff' around with the probe and move towards where the signal's stronger.

Any thoughts on how likely this is to work? I don't have a good feel for whether I'd be able to get a reasonable signal level out of the far end of the cable to make it detectable.

Would any particular waveform and/or frequency be more optimal? I assume this is a pretty standard 75Ω coax cable intended for cable tv signals. Any guidance on maximum amplitude/power of the applied signal to avoid damaging the cable (or something of importance/value it may still be connected to on the other end)?

I don't have any sort of field probe on hand at the moment. Any guidance on what I'd need for equipment to pull this off? I may be able to borrow from our EMC lab at work if necessary, but also don't mind buying if relatively cheap. Also seen a few sites describing how to make your own EM field probes, but I still don't have a scope or anything capable of measuring high speed signals.

Thanks in advance for any help you can provide.


Joined Mar 30, 2015
Do you have any idea how the other end of the cable is terminated? I'd suggest using a TDR (Time Domain Reflectometer) to find out how far the other end is and make some educated guesses. Service technicians for a phone/cable company will have them. If you have a scope, you can make your own. You just send a pulse down the coax and look for the reflection. The time the return signal takes will give you the length of the run.


Joined Feb 25, 2011
before you spend money, have you tried pulling the cable see if its cut just inside the wall
( I had this in a previous house, seems owner used wifi, not the cable so never noticed !! )