EDUDEAF: FM Interference

Key words: Information, Technologies for Deaf/HH

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Date: Sat, 12 Oct 1996 08:50:27 -0400EDUDEAF: FM Interference
Reply-To: A Practical Discussion List Regarding Deaf Education
Sender: A Practical Discussion List Regarding Deaf Education
Subject: FM interference
To: Multiple recipients of list EDUDEAF

Usually I just lurk, but I have a major problem and need help!

Refresher intro: Linda Center - "oral" Preschool/Kindergarten IH in "regular school" (Atlanta area); mild to profound loss; use: aids, FM, CI; 2 teachers, 2 SLP(part time), 2 parapros and 10 students; "tons" of support from school. Seems to be a perfect setup but alas nothing is perfect. There are always problems.

Our FM system (Phonic Ear) at school is receiving interference from somewhere in the neighborhood. The system has been checked out and frequencies replaced (still a few frequences to try but am waiting on the county to place order :( Big wait!) We have checked all "things" in the school we can think of and tested by turning off and on all gadgets.

Tried: Change mics, transmitters, recievers, battery pacs, frequencies, cords.

Turned off and on: lights, walkie-talkies in school, cell phones, microwaves, (desperate - pagers) Checked: computers, TVs, radios. Really desperate here!

Occurres: usually from 9 - 10:30 AM, (some times; other times - off & on) all over the building and grounds. Is often picked up by school walkie-talkies.

Any suggestions for "fixing" this. How to find the offender? How to avoid the interference?

Help! Reply to list or my email - lgcen@mindspring.com

Thanks in advance,
Linda in Atlanta

Document 2 of 13

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Date: Sat, 12 Oct 1996 22:16:32 -0700
Reply-To: A Practical Discussion List Regarding Deaf Education
Sender: A Practical Discussion List Regarding Deaf Education
Subject: Re: FM interference
To: Multiple recipients of list EDUDEAF

Linda,

I am working the same problem for a speech school in NJ except it is with Comtek FM's. After trying all the usual culprits I suggested calling the power company and blaming it on them. They came in and could not find the problem but they said they will come back with more sophisticated instruments. The Comteks operated on 40 narrow bands and 10 wide bands between 72 and 76 MHz.

Stay in touch.
Jay
Keep me informed

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Date: Sun, 13 Oct 1996 16:12:58 -0400
Reply-To: A Practical Discussion List Regarding Deaf Education
Sender: A Practical Discussion List Regarding Deaf Education
Subject: Re: FM interference
To: Multiple recipients of list EDUDEAF

I've run into problems with several of the things you've checked and ruled out. Also, in one school we went through a similar experience to yours - changed everything we could think of including the entire receiver/transmitter system, to no avail. SLP and I insisted it had to be something in the buildings electrical system - custodians and facilities supervisor insisted not so - they'd checked everything and the wiring was all fine. After several very long months, quite by accident we were testing the whole FM system again one day when the noise cleared up abruptly - and the school-wide ventilation system shut down. SLP ran to find out - electrician working on system had shut it down. We explained our ongoing problem, so he gave us (but not the child) a high sign before turning back on - noise started again. Shut down system, noise stopped. We never did find out specifically why it was happening, and I wasn't there for the solution - maybe some kind of shielding? Anyway, another variable to look at.

Are you reasonably sure it's in the building and not in a nearby business or something? Not that I know how to test for that, especially if changing frequency doesn't work.

Good luck!
Robin
henne@moose.ncia.net

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Date: Sun, 13 Oct 1996 20:13:24 -0400
Reply-To: A Practical Discussion List Regarding Deaf Education
Sender: A Practical Discussion List Regarding Deaf Education
Subject: Re: FM interference
To: Multiple recipients of list EDUDEAF

Any radio stations nearby and/or someone using cellular phones?

Linda S

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Date: Sun, 13 Oct 1996 20:19:12 -0400
Reply-To: A Practical Discussion List Regarding Deaf Education
Sender: A Practical Discussion List Regarding Deaf Education
Subject: Re: FM interference
To: Multiple recipients of list EDUDEAF

It's probably a ham radio operator or more likely a CB operator with a big linear amplifier. You can drive around looking for antennas but even if you find the source, what will you do then? If it's a ham, they have every right to use their rigs. If it's an illegal CB operator, you can have them shut down but they may show up again some other time.

Can you move the classroom to the basement or to an inside classroom? That's not exactly the nicest environment but it may help. You can test it when the offender is broadcasting. You might find a room on the other side of the school which may have a large mass of metal in the way of the radio waves and effectively blocks the broadcast.

Good luck,

Chris
<< Chris deHahn.....CdH.....System, Network, CAE Administrator >>
<< Sun Microsystems, Inc....dehahn@tiac.net...'91 Buell RS1200 >>

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Date: Sun, 13 Oct 1996 20:28:17 -0400
Reply-To: A Practical Discussion List Regarding Deaf Education
Sender: A Practical Discussion List Regarding Deaf Education
Subject: Re: FM interference
To: Multiple recipients of list EDUDEAF

Maybe I overlooked it, but what kind of interference are you getting...static, people talking, ticking, etc. I know Alex was complaining that his trainer kept ticking...his teacher kept insisting that it was fine and he was just making an excuse for not listening. So, I went in and played around with it and determined that the plastic neckcord she wore for the mic was hitting the mic when she walked and thus making a loud Tick/Tick/Tick as the mic swayed. When she was still as she would be when she tested the mic, it did not do this...only when she moved.

Also, as I mentioned, radio repeater stations and cellular phone towers can also cause potential interference as well as the ham operators/CBers Chris mentioned. Could even be taxi drivers or construction workers or types that use handheld radios. But, if you're more specific as to what you mean by interference, that should narrow it down. If it's people talking, then it's definitely not the air conditioning.

Linda S

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Date: Sun, 13 Oct 1996 22:12:46 -0400
Reply-To: A Practical Discussion List Regarding Deaf Education
Sender: A Practical Discussion List Regarding Deaf Education
Subject: Re: FM interference
To: Multiple recipients of list EDUDEAF

> Occures: usually from 9 - 10:30 AM, (some times other times - off & on) all over the building and grounds. Is often picked up by school walkie-talkies.

Is there anything at the school that generally happens during this time? How about stores....usually around here, they open from 9-10:30...is there anything that's opening then. Are there any special people who go to work around this time....who might use walkie talkies....construction people, tree experts, gas and electric men, delivery vehicles, buses with walkie talkies, county maintenance personnel; any large facilities that might start up generators then. Really makes a difference if the noise is voice or just signal interference. Does the fm signal of the ALD cut out or do you actually hear static, buzz, hum, tick, voice...what? When it happens with a walkie talkie, can they make it louder/softer by walking different directions? Any taxi operators nearby that might be doing their am calls? Aah well, can guess some more once I know what the noise is...I'll ask hubbie too as he's an Electrical Engineer who is in Robotics where signal interference is really important for ensuring consistent remote control operation.

Linda S

Always ready to tackle a mystery!

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Date: Mon, 14 Oct 1996 10:07:57 -0500
Reply-To: A Practical Discussion List Regarding Deaf Education
Sender: A Practical Discussion List Regarding Deaf Education
Subject: Re: FM interference -Reply
To: Multiple recipients of list EDUDEAF

Another suggestion is to check the frequency with Phonic Ear and find a frequency tht is the farthest away from that number. Also have you called the company for suggestions ?

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Date: Mon, 14 Oct 1996 22:41:17 -0700
Reply-To: A Practical Discussion List Regarding Deaf Education
Sender: A Practical Discussion List Regarding Deaf Education
Subject: Re: FM interference
To: Multiple recipients of list EDUDEAF

> Are you reasonably sure it's in the building and not in a nearby business or something? Not that I know how to test for that, especially if changing frequency doesn't work.

> Robin
henne@moose.ncia.net

Robin,

I'm very sure that it is in the building. When it happened the last time one of the teachers took the transmitter and receiver outside the building and it went away. Took it back in and it came back. The problem is the interference is so intermittent...we havn't had it for three days now. I think we could track it down if it would persist but that's what makes life interesting.

I'm thinking about having all the circuit breakers flipped, one at a time, the next time the interference happens. First, we have to identify all the breakers so that we don't trip any computers or the two servers without adequate notice.

Jay

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Date: Tue, 15 Oct 1996 14:52:11 -0400
Reply-To: A Practical Discussion List Regarding Deaf Education
Sender: A Practical Discussion List Regarding Deaf Education
Subject: Re: FM interference
To: Multiple recipients of list EDUDEAF

If you know an electrician, you might ask if there is some kind of field meter or other device that would help you locate the source of your interference. Of course, as you say, the intermittancy will make you crazy.... Failing all else, flipping breakers as you describe should give you some information. Good Luck - I do know how crazy this kind of thing can make you and the poor kid trying to use the FM.

Robin
henne@moose.ncia.net

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Date: Tue, 15 Oct 1996 17:50:24 -0400
Reply-To: A Practical Discussion List Regarding Deaf Education
Sender: A Practical Discussion List Regarding Deaf Education
Subject: Re: FM interference
To: Multiple recipients of list EDUDEAF

Thanks to everyone for the help on tracking down the interference ( static not voices) on our FM system. I have tried most of the suggestions and will check out the rest. In the meantime.......

Phonic Ear is going to send a scanner for us to use. It will scan and identify the frequencies broadcast to my room. They are very eager to help us solve the problem. At least this way we may find a frequency that is clear of interference. If I ever find the problem rather than just avoiding it, I will share the results.

I'll take anything at this point. Parent conferences are this week and the parents want answers to this problem yesterday. That's okay, but it's making me crazy.

Thanks again,
Linda in Atlanta

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Date: Tue, 15 Oct 1996 19:31:58 -0400
Reply-To: A Practical Discussion List Regarding Deaf Education
Sender: A Practical Discussion List Regarding Deaf Education
Subject: FM Interference
To: Multiple recipients of list EDUDEAF

Got a letter from Tina Davis, an EduDeaf Subscriber, with packets of informational items in it. One of them discusses potential FM interference sources:

"Sometimes, the transformers in fluorescent lights can interfere with FM systems. Characteristically, they produce a humming noise. This can sometimes be remedied by replacing the transformer in the light fixture or by having the student move to a different location in the classroom."

"Some desktop computers, esp older ones, can cause interference with FM systems. Check this by listening to the FM equipment in the vicinity of the computer. The interference is a high-pitched squeal."

Thanks for the packet Tina!
Linda S

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Date: Wed, 16 Oct 1996 17:24:19 -0600
Reply-To: ccumming@jeffco.k12.co.us
Sender: A Practical Discussion List Regarding Deaf Education
Subject: Re: FM Interference
To: Multiple recipients of list EDUDEAF

Hi all,

We had the same problem and traced it to the fluorescent lights!! Occasionally, replacing the bulb with a newer one fixes the problem. Hope this info helps!

Candie Cummings

Uploaded by: Jessica Soltesz/Kent State University/Deaf Education Major