Radio Signals on Phone line

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I was told that more 'grounding' of the phone cable would help reduce the interference on phone cables that pick up radio signals. Is this true??

We have a situation where in a house the phone line picks up faint radio signals on it, and Im not really sure how to stop it. its even been disconnected from the main line feeding the house and yet it picks up the radio signals.

Anyone have any experience in dealing with this?? And how to correct it??
 

cadpoint

Senior Member
Location
Durham, NC
Make sure you got a good Ground... < can I even say that any more ... :)

Recrimp all the pins on at your D-mark.

Ask if any construction happened, sometimes one might nick a wire, or a rube some where out yonder. The open short is always long enough to a freq. ...

Kill the Service and read each circuit back through two phones one with a battery. The phones will quailify the line.
 

hurk27

Senior Member
I was told that more 'grounding' of the phone cable would help reduce the interference on phone cables that pick up radio signals. Is this true??

We have a situation where in a house the phone line picks up faint radio signals on it, and I'm not really sure how to stop it. its even been disconnected from the main line feeding the house and yet it picks up the radio signals.

Anyone have any experience in dealing with this?? And how to correct it??

Most phones with amplifiers in them will have an AM detector diode at its input to the amplifier, this makes a great demodulator for AM radio signals when they are strong enough on the phone lines and sometimes just the phone itself if powered by a wall outlet, many cheep phones don't have much if any RFI filtering and can be the source of the trouble, trying a different phone will sometimes show this, other remedies start with a little trouble shooting, using the receiver part of a good toner which also uses an AM detector diode before an amplifier, you can see (or hear) which phone cables are affected, by placing a phone RFI filter at the demark and at each jack you can eliminate almost all of it, these filters can be purchased at most electronic part supply houses, sometimes Radio Shack has them in stock, the tunable ones can be dialed in with dip switches for the AM band (530kz-1650kz) you can also get them off a phone truck if you see one in the area, (My first choice) as they will just give them to you since your saving them the time to trouble shoot this problem

We have one AM radio station that beams its signal right across two neighborhoods, and it can even affect some garage door openers like a Genie, It gets into the digital signal for the safety eyes, I use the same phone RFI filters for them also, as well for networks with speed problems in this area.

Also if customer has satellite TV, and the receiver is using a phone line for PPV, try disconnecting this line from the back of the satellite receiver, if this clears it up, put a RFI filter in that phone jack, those satellite dishes love to bring in this AM signal and transfer it to the phone lines.
 
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hurk27

Senior Member
One other thing, most phone drops and underground feeds from the main line are already grounded as much as can be done, they will have an outer metal jacket that is bonded at the demark and at the pole, or tap box, there is no grounding of anything you can do after the demark, ring or tip can not be grounded or all kinds of problems will happen, and like you almost every time I have had this problem disconnecting the inside phone wiring from the demark does nothing to help.

Only when the phone installer temps a line across the yard on top of the ground, sometimes this line is not shielded or grounded, but disconnection from the demark will show this as the problem. Here on new construction I have ran into this, but then a call to the phone company will usually get this problem fix very quickly when you explain to them its the problem, FCC requires a 24 hour turn around on phone repairs if it can be shown to be their problem.
 

hillbilly1

Senior Member
Location
Atlanta,Ga
Occupation
Field coordinator/ technical support
If you can tell what station it is, call them, the FCC requires them to repair or correct any problems like this.
 

K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
Jim Brown is the Audio Engineering Society (AES) committee chair on EMI/RFI interference. He is also a HAM, he has several papers on interference:

http://www.audiosystemsgroup.com/publish.htm

If the radio station is operating properly and it most likely is then the FCC willnot make the station fix your problem.

The FCC will NOT contact ANY radio station due to interference to a telephone. In order to be legal for sale in the US, the phone has to be able to tolerate any radio interference. (CFR 47 Part 15)

Do NOT ground any of the phone lines. They are floating. Grounding one will surely get a visit from the phone company and warning not to do it again. Do NOT touch ANY of the wiring that is on the phone company's side of the TNI (the grey box the line comes into). That wiring is the property of the phone company.

I am also a ham radio operator, an Extra Class to be exact. I teach FCC rules. PM me and I will get my phone number to you if you want to talk more. I have a bit of experience solving RFI issues, but I'll bet your only recourse is to purchase a telephone that is legal.
 
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Electric-Light

Senior Member
And how to correct it??

Try a different phone. That worked for me. I have a mid 90s GE/Thomson Consumer Electronics corded landline phone. That thing will pickup buzzing from light dimmers and pickup sound from a nearby radio station.

All the other telephones in the house don't.

Also, my computer speaker will pickup walkie talkie signal sometimes. Sometimes faint, sometimes very clear, loud voice coming through speakers, even with the computer turned off. It will also pickup the "click, pop" noise when my thermostat's relay operates. Changed the signal cable to shielded one but that didn't help. It's just a poorly shielded amplifier. The solution is to replace the speaker, but it doesn't bother me enough to drop the dough to get a new pair.
 

K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
Try a different phone. That worked for me. I have a mid 90s GE/Thomson Consumer Electronics corded landline phone. That thing will pickup buzzing from light dimmers and pickup sound from a nearby radio station.

All the other telephones in the house don't.

Also, my computer speaker will pickup walkie talkie signal sometimes. Sometimes faint, sometimes very clear, loud voice coming through speakers, even with the computer turned off. It will also pickup the "click, pop" noise when my thermostat's relay operates. Changed the signal cable to shielded one but that didn't help. It's just a poorly shielded amplifier. The solution is to replace the speaker, but it doesn't bother me enough to drop the dough to get a new pair.

You may be able to take care of your speaker issues with toroidal chokes. PM me and I'll tell you how to do it with chokes from Radio Shack. I have to use them on my speakers when I transmit 100 watts and the radio is within a few feet of the speakers. But it's worth it considering I am using the power of a light bulb and and an antenna made of leftover THHN to talk to another station 5 to 10 thousand miles away.
 
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MR2Di4

Member
Some phone line radio noise can be eliminated by verifying that only the active pair (often Red/Green or White/Blue) in use is hooked up at your jacks. Make sure all the connections are clean inside the customer side of your phone box (Network Interface Device) and at any jacks in your house.

Most phone cables have at least four conductors, often as many as eight, running alongside each other from jack to NID. Part of the reason phone wires are twisted is because doing so generates a small EM field around the active pair that provides some resistance to outside signals. Older telephone wiring with less twist on the pairs more susceptible to picking up RF for this reason.

However, if there are more inactive wires tied down to jacks, but left floating at the NID, they act as antennae and can introduce radio noise as well. It may also help to disconnect any cabling going to unused jacks at the NID since you are a) reducing the amount of wire that can pick up radio noise and b) de-energizing empty jacks that are magnets for dirt and corrosion when left active but unused.

Be wary of using RF filters (sometimes referred to as radio chokes) on lines using DSL because they will often severely hamper the modem's ability to communicate as DSL signalling frequencies extend into the AM radio realm.

This is a good article I found on the subject...
 

cadpoint

Senior Member
Location
Durham, NC
...

... Do NOT touch ANY of the wiring that is on the phone company's side of the TNI (the grey box the line comes into). That wiring is the property of the phone company.

Did the op cure their problem ? :)

I had static on the phone line it was the ground connection in the grey box and a bad splice, I touched it. In talking to the phone tech they assured me it was on my side in that they rang the lines with computers, routinely.

Another static situation was a interior animal had pucked on a phone jack...
 

K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
Did the op cure their problem ? :)

I had static on the phone line it was the ground connection in the grey box and a bad splice, I touched it. In talking to the phone tech they assured me it was on my side in that they rang the lines with computers, routinely.

Another static situation was a interior animal had pucked on a phone jack...

Ah, the 'point of demarcation'. Gray area, gray box.

I'm just sayin'....

You weren't touching the wires at the same time the phone was ringing, were you?
 

jaylectricity

Senior Member
Location
Massachusetts
Occupation
licensed journeyman electrician
In Hull, MA, WBZ can be heard on all phone lines and also faintly over a lot of radio stations. The towers are located there and it has been a problem as long as anybody can remember.
 
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