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Author Topic: Phone RFI  (Read 1774 times)
AB3CX
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Posts: 638




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« on: December 27, 2007, 09:27:23 AM »

I have one neighbor who complains of RFI in her phone. This occurs only when I operate SSB, never CW. She hears a garbled voice. This happens when I'm QRO in contests, doing alot of hours in a weekend. Otherwise for the occasional SSB QRO QSO I guess she misses it. My antenna is a log periodic up 55 feet on a tower, or a HyTower. Both are fine antennas. The neighbor lives 2 homes away on our village block. No one else in the neighborhood has reported phone RFI. I put filters on each of her phones, and heard nothing for a year, but during a recent SSB contest got an angry phone call. My question is, why her and no one else, and what is the limit of my responsibility to clear it up? Is there anything else likely to work?
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W3LK
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« Reply #1 on: December 27, 2007, 12:51:50 PM »

With what you have already done, I think you have no further responsibility. Part 15 devices, which telephones are, must accept any interference from licensed sources.

As long as you have no problems in your own home, I wouldn't expend any further time and energy on the matter.

I'm betting there is a bad ground somewhere in her phone system, but that is HER problem and not yours, as it was in the first place. Personally, the first time around I would have described the filter solution and let her buy them and install them. I would not have done it for her.

73,

Lon - W3LK
Naugatuck, Connecticut
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AB3CX
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« Reply #2 on: December 28, 2007, 09:13:06 AM »

In my own home, no one ever hears me on the phones!!
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KC2MMI
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« Reply #3 on: December 28, 2007, 09:53:51 AM »

Could be your signal is getting into the phone lines, I'm guessing they run aerial lines between poles in your village? And then for whatever reason, the signal is getting into her house. Could be a resonant length of phone wiring is making itself into an antenna--just on her run. Or a bad ground.

If you can explain to her that the problem is the phones--not you--but that you are willing to try fixing it with her if she'll co-operate...that's probably going to be the best long-term answer.

There should be a junction ("demarcation") box on her exterior wall, where the phone line comes into the house. If she agrees, get someone to help you check at that point. The interior home wiring can be disconnected, and a test set or regular phone plugged in at that box. Get your friend to use a phone at the box while you transmit--which will confirm if the problem is coming in from the exterior wiring, or is internal to her house.

If it is on the exterior box...you may need to call the phone company. If the problem is internal to her house--that's a harder one, checking wiring and seeing what can be done with filters, new line, grounds, or phones.
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W3LK
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« Reply #4 on: December 28, 2007, 06:28:25 PM »

<< Thanks for the suggestion for checking at the outside box, that is brilliant. >>

That is TELCO property; let the phone company check it, especially on someone else's property!
73,

Lon - W3LK
Naugatuck, Connecticut
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KC2MMI
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« Reply #5 on: December 28, 2007, 06:52:56 PM »

Lon, while the demarcation box may be telco property, if you call the telco to report trouble on the line almost all telcos these days (and for well over a decade now) will ask YOU if you have checked at the demarcation point to see if the trouble is inside or outside the premises.

They don't care who plugs into the box, there's no damage you can do that will cost as much as sending out a repairman costs. That was the whole point of the lawsuits against AT&T forty years ago, when AT&T said "Well if you plug in unauthorized equipment you could black out the entire country" and then they reluctantly had to concede that there's pretty much nothing a telco customer can do that will hurt the system. Even back then.

The exterior boxes installed on home walls (that I've seen and used) all are split into two sections. One section that the homeowner or other party can easily open, and a second section where the drop lines are secured into the box. That second section is usually harder to access. The first section usually has a standard RJ-11 jack in it, and the premises wiring is plugged into that socket with an RJ-11 plug, so you can UNplug the premises wiring and then plug in any standard phone and test at the box.

The purpose of the box is to save them money on repair calls, because if you say "the trouble is inside the premises" they will promptly offer to send a repairman out--on your dime. Either way, the box saves or makes money for them, that's why it is there.
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WA7NCL
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« Reply #6 on: December 28, 2007, 12:10:49 PM »

The neighbor is probably using a very cheap phone that is very suseptible to RFI.  Maybe take one of your phones over there and see if it has a problem.  If it doesn't give her that one and buy yourself a new one.

Some consumer devices just can't be cured of RFI without a redesign.
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W3LK
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« Reply #7 on: December 28, 2007, 12:32:30 PM »

I agree with trying out another phone, but I do NOT agree with providing her with a replacement. You set the precedent for her to insist you replace anything else she has in the house that might, in the future, fail and become an unintended receiver.

It is NOT your responsibility to fix her problems, if your station is clean and causes no problems in your home.

73,

Lon - W3LK
Naugatuck, Connecticut
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AB3CX
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« Reply #8 on: December 28, 2007, 05:49:35 PM »

Thanks for the suggestion for checking at the outside box, that is brilliant.
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W3LK
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« Reply #9 on: December 29, 2007, 06:44:52 PM »

I am more than well aware of why the box is there, who owns what and all the rest. I worked for a TELCO for several years.

I still would not touch that box on SOMEONE ELSE'S property.

73,

Lon - W3LK
Naugatuck, Connecticut
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KF7CG
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Posts: 872




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« Reply #10 on: December 31, 2007, 10:22:42 AM »

The phone RFI checks should be made at the point of emarcation with a known good telephone and all other devices disconnected.

One problem with locating telephone RFI is that very often the offending device couples audio back into the phone line thereby causing every phone in the system to appear to have RFI.

By the way I have found that the ring detect circuits of telephone answering machines to be epecially bad in this respect. Very often disconnecting the answering machine cleared all the interference from many telephones.

In an area where of the air television reception is prevalent a similar phenomenon occurs when poorly designed/installed antenna boosters oscilate when hit with strong signals.
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AA4PB
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« Reply #11 on: December 31, 2007, 11:17:22 AM »

You have to be careful on a neighbors property but my attitude is as long as my neighbor is being friendly and cooperative I'll be cooperative and try to help resolve the issue. If she calls the phone company they'll charge her and tell her that it is YOUR fault - that she should call the FCC to have you put off the air. While the FCC won't do that, you'll have a very hostile neighbor from that point on. Once she has been told by the "professionals" that it is your fault you aren't likely to convince her otherwise.

If you can plug a good quality phone (perhaps one of your phones) into the demark point and demonstrate to her that it is free from interferrence then she may realize that the phone makes a difference. She may then be willing to purchase a new phone.
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