Key words: Information, Technologies for Deaf/HH
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Date: Sat, 12 Oct 1996 08:50:27 -0400EDUDEAF: FM Interference
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,
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Date: Sat, 12 Oct 1996 22:16:32 -0700
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.
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Date: Sun, 13 Oct 1996 16:12:58 -0400
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!
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Date: Sun, 13 Oct 1996 20:13:24 -0400
Any radio stations nearby and/or someone using cellular phones?
Linda S Document: 1 2 3 4 5 6 7 8 9 10 11 12 13
Date: Sun, 13 Oct 1996 20:19:12 -0400
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
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Date: Sun, 13 Oct 1996 20:28:17 -0400
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
> 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! Document: 1 2 3 4 5 6 7 8 9 10 11 12 13
Date: Mon, 14 Oct 1996 10:07:57 -0500
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
> 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
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
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
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Date: Tue, 15 Oct 1996 17:50:24 -0400
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,
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Date: Tue, 15 Oct 1996 19:31:58 -0400
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!
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Date: Wed, 16 Oct 1996 17:24:19 -0600
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
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Linda in Atlanta
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Jay
Keep me informed
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Robin
henne@moose.ncia.net
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<< Chris deHahn.....CdH.....System, Network, CAE Administrator >>
<< Sun Microsystems, Inc....dehahn@tiac.net...'91 Buell RS1200 >>
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