sundance-communications.com/forum Forums Wiring - Telecom Carriers - Trunks & Services Cabling Telephones Systems Wiring Radio station interference on phones

A few of our guys installed an ESI 200 system in an office/warehouse type environment. When they turned on the system and tested the phones, the warehouse exts all had radio station interference on them. They tested those exts directly at the block and they were fine.

There is a radio station located directly next door. What is the best way to approach this? Do we need to run all shielded cable? We also ran data, will that cable also have to be replaced with shielded?

One more thing, the electricians ran their main cable right next to our voice and data in the warehouse to the point where it butts up right against our cables in some places. I know this is no good but could that be causing a problem like this?

TIA...

First, "right next door" , is that in the same building or in the next building or in the next block? In other words, is it the full bleed over of the amplification or is it a harmonic response?

Odds are the electrical conduit has nothing to do with the problem. As these are only the warehouse wires, ground every pair not in use. Also, did you use Cat 5 or better for the phones? Probably not. The tighter the twist the less chance of a harmonic intrusion.

If grounding the excess pairs doesn't do it, go for the grounded / shielded cable.

My two cents.

If you run shielded cable make sure that you ground the shield at the KSU end and safe it off at the station end. Otherwise it can act as an antenna and make the problem worse.

I would test each option offered one at a time. You may need to combine several till you find the right set. You also may need different solutions for different cable runs.

It's also possible to buy radio "chokes" that are set for the exact frequencies of the interference you're getting. They will eliminate the trouble completely.

Sam

Next door as in next lot, not attached. They ran cat3.

I think we'll start with grounding unused pairs, I've never done that before. I know how to ground them at the back board but what do I do with the pairs at the jack end? What do you mean by "safe it off" Sam?

Thanks guys...

Ground at the KSU only...."safe" = clear the ends.

Keep them from touching anything else. Taping them to the cable would do.

Sam

Try a ferrite choke put one on each end of the wire with a couple turns of wire through the choke.

I have had very good luck with these .

Mike -

Those look really slick! The stuff I had to work with years ago wasn' half as convenient.

Sam

They work really good too.

We had a customer a year or so ago that was located really close to US 23 which is a major highway in east KY that is also a coal pipeline to the docks in Ashland.
A lot of these truckers would have a 100 to 200 watt booster on their CB radios and when the truckers would key up in front of the customers office it would come across their phones. Even the idle phones across the speaker phone.
We put these on and it cured the problem.
We did have to put them on the CO lines and the stations, but it took all of the interference out.

The main thing is, that you must know what frequency your trying to filter out.

With a radio station it's a lot easier.

Sam

I used the same as mdaniel. Works really good.
I used to have a client with the same problem but with no Radio station next door. Was electrical ground issue.

I don't know if I even want to get into this.

Went there yesterday, the system wasn't properly grounded, we grounded it and I never heard any radio station interference after that. By the way, this is a major station, with two 600' towers about 100' away from the building.

What is happening now is some phones are going crazy, the lines sound clean but some phones freeze up or get strange icons on the display. Do you think that RF can be causing these random problems?

Also the CO's don't even ring in on the system but I've narrowed it down (hope I'm right) to low ring voltage from telco, I'll post this in a new thread.

RF will absolutely cause intermittent problems exactly like that.

Use this RF choke from radioshack and your problems should go bye bye.

We had a customer with phones going off-hook to intercom randomly ---> two of those RF chokes and no more ghost in the machine. 2 days and 3 hours of troubleshooting, then $10 worth of radioshack parts... priceless.

PS - the exact same ones that others (merritt, michael, sam) have suggested.

Thanks everyone for your input. I'm on 1 day and 2 hours troubleshooting. I will try these solutions and post back.

This site = priceless.

Can't remember who makes them, but I've had good results with something that Graybar used to carry. The part number was 'PORFF'. Worked for AM and FM. Didn't always work, and sometimes had to put 1 at the jack AND 1 at the X-Connect. John C.