sundance-communications.com/forum Forums Wiring - Telecom Carriers - Trunks & Services Outside Plant OSP Construction Radio Interference

I have a stretch of 25 pair cable running under ground from the client's bay area to the demarc room. This stretch of cable is acting as an antenna and picking up radio signals. I have done all kinds of testing and have worked it back to this underground cable. If memory serves me correctly the underground conduit is PVC. Has anyone experienced this or have a solution to this problem. I have a ground on the phone system and I have tested it and it is good however it is not preventing the radio signals interfering on the phone lines.

Is the cable the type that's designed for outdoor installations (black polyethylene sheath with aluminum or copper shielding)? If it is, please make sure that sheath bonding clamps have been installed on the cable at both ends that that they are bonded to the building's electrical grounding system.

If it's just plain indoor wiring cable, then it's likely that water has infiltrated the conduit and the cable's jacket. When this occurs, nearly anything can happen. In this case, the cable should be replaced with the proper material.

Thanks Ed, I have discussed changing the cable out with the customer but I was hoping that there would be an easier solution. And yes it is just plain indoor cable and you are probably right.

Just for giggles, ground all unused pairs and see what you get.

But Ed is only too right......wrong cable, wrong application.

Good Luck.

My father has had this same problem since 1986, sadly he has been an OSP man his entire working life but the telco owns the cable so he dare not play with it. But on the bright side of things, if you are bored and lonely at his house the Kumbia music on the telephone line is fantastic listening!

When I first started in this business I had this happen to me thought it was the cable but turn out to be the mic on the phone (Starplus). Radio station was an AM oldies format.

I want to thank everyone for their help. It turns out that this problem was throughout the community and has been for years and nobody has done anything about it. We got the dial tone provider involved and they had corrected the problem.
Thanks again!!

Thanks for letting us know the outcome!

Sam

I know this is an old post, and the problem has been resolved, but I thought I would add a few more things to look for that might help someone else in the future, if they read this topic to find answers to a similar problem.

It was already mentioned that one of the phones can pick up radio (especially electornic phones like we have today). So if the radio is coming from inside, be sure and unplug all the equipment that is connected one at a time to see if the problem clears up. Another thing that can cause this on the inside is the old non-twisted four conductor station wire. It can act as an antenna and pick up the signal and bleed it back into the line. An unbalanced station wire or cable pair will also pick up radio, if there is a strong radio influence in that area. As far as the outside plant goes, first check and see if the problem is isolated to certain pairs or the whole cable. If it is just isolated pairs, make sure your pair is free of all resistive and capacitive faults. If everything checks out with the cable pair and it is isolated to this pair or a certain count check and see if the affected pair or count is multipled down another leg(the infuence could be coming from there). If the whole cable has radio bleed over, then check your bonding and grounding for current flow to make sure you don't have an open sheild or bond. It has been my experience that most technicians don't know how to properly test bonding and grounding. In most cases you should have current flow on your shield if it is properly bonded and grounded and has good shield continuity. This is tested with a clamp on amp meter. Most techs think you can simply look for the ground at the next ped or closure to test for good shield and or bond continuity, but that is not a good technique to properly test bonding and grounding. Getting back to radio bleed over, if your plant checks out good, the radio station may have a problem on their end. If you can't get them to resolve the issue then you may have to add a radio supressor to the line at the NID, or even at the jack if that doesn't clear it up.

You can make a simple toroid-choke using one of these from Radio Shack and some cross connect wire. Wrap the wire through the toroid-choke case around 10 to 20 times and install at NID. What you're making here is a low pass filter that will black the AM radio signal from enter the home. You might have to place one at the set if you're still having issues.

https://www.radioshack.com/snap-together-toroid-choke-core-2-pack/2730104.html#.VPOmSI5TuDE

An example of what to make... this one has 3 wires, you only need 2.
https://cdn.instructables.com/F1Z/P9UI/GI0TM07H/F1ZP9UIGI0TM07H.LARGE.jpg