Phone line RFI problems

[techie2]

Anybody got some good suggestions for troubleshooting phone line RFI issues?

Got a Circuitwerkes DR10 that is being used for dial-up sports remotes. It was recently moved from a temporary location at the transmitter site to the studio end. During the connection process and testing we found that we're getting some sort of intermittent RFI anytime the phone line is patched to air. Sounded like some yahoo on a juiced-up CB.

I'm sure our resident ham will be having a little DF-ing fun trying to track the guy down. So far I've figured I should check to make sure the phone line wasn't punched onto an unbalanced pair somewhere in the building (the space was converted from a cube-farm office and had a lot of extra jacks installed), and to swap the line cord to the Circuitwerkes with the twisted pair cord with chokes on each end that I was using at the transmitter site.

 

[phatdaddy]

See if your resident ham has a copy of the American Radio Relay League's Radio Amateur's Handbook. They have a lot of information concerning RFI including schematics for phone line filters and tricks for minimizing the problem.
Do you hear this interference on any phone that is plugged into this particular line? If you only hear it on that one particular piece of equipment, then a modular in-line filter placed inline with this device would probably be effective.

 

[techie2]

I was able to get some of the handbook information on RFI off the ARRL web site. I did look at a couple in-line traps.

Didn't get any of the interference on the regular phone, but we weren't sure if he had shut down for the night by that point or not. Next time we have time to test, I'll take my scanner with me and see if I can match the audio and figure out what frequency it's on.

 

[NE Miss Radio]

I didn't see it specifically mentioned in the post so I'm going to ask...are you sure it's on air and not just in the headphones/monitor speakers? We used to hear lots of CB'ers in the studio phones and monitors but it was only in them and not in the (better protected) air chain.

 

[techie2]

I can only assume that it would go out over the air, since it was showing on the mixer VU meter and the processor input metering.

 

[TowerLamp]

techie...Radio Shack sells a very effective phone line RF filter. We send all our RF complaints there and it solves about 90% of them. We keep a couple in the shop to give free to polite complainers. The really pissy ones we send to radio Shack to buy their own ;D

 

[techie2]

techie...Radio Shack sells a very effective phone line RF filter. We send all our RF complaints there and it solves about 90% of them. We keep a couple in the shop to give free to polite complainers. The really pissy ones we send to radio Shack to buy their own ;D

Thanks...guess I didn't think of the obvious given that Rat Shack is generally just cell phones nowadays.

I borrowed a line filter from someone who said the phone company gave it to him to get ham interference out of his phone at his old house. I'll see if it works.

 

[OnTheAir123]

The Radio Shack filters work pretty well but be sure to experiment. Sometimes they work best if plugged into the wall jack and the line cord into them and sometimes they work better if plugged into the phone and the line cord from the wall into them. Cat# 43-150, most effective from 3-30Mhz but do work for broadcast AM.

Another company called K-Com makes 2 nice little RF filters. One is like the Radio Shack, a small little filter with a RJ-11 "tail" running out of it. The other is one that can be used on punch down blocks and it has "flying leads" in and out so you can unch them down. I have those installed on my "Problem Lines" coming into the building. The K-Com units ARE rated to cover the AM broadcast band where the Radio Shack units are centered for 3-30Mhz.

K-Com
3568 Randolph Rd.
Mogadore, OH. 44260

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