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Posted by Steven Lichter on June 22, 2008, 8:59 pm
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T wrote:
> joeofseattle@yahoo.com says...
>>
>> <<I think most telephones these days use electret transmitters too. Of
>> course, the fidelity is limited by the audio bandwidth available from
>> the telco. The transmitter is usually capable of far better.>>
>>
>> While you do get better voice fidelity with electret microphones
>> unfortunately you get worse RFI rejection. Put a GSM mobile phone
>> next to a handset such as a recent 'K' style handset and place a call
>> to the wired phone. Just prior to the phone ringing you'll hear the
>> classic GSM "ditdidit-ditdidit-ditdidit" RFI prior to the wired phone
>> ringing. You probably won't hear that on a phone that has a carbon
>> granule transmitter.
>>
>>
>> ***** Moderator's Note *****
>>
>> Since I'm a ham radio operator, this subject is very near to my
>> heart. There's nothing like the "thrill" of working all day long to
>> put up a new antenna design, and fire up the rig, only to hear
>> my son crying "DAAAAD" since he can hear me on the phone while
>> trying to talk to girlfriend #307.
>>
>> In general, Western Electric "500" sets are the least troublesome
>> I've worked with, and the cheap "giveaway" phones that people
>> used to get in return for trying a magazine subscription are the
>> worst.
>>
>> Whatever the instrument that you're having trouble with, there's a lot
>> of practical advice available from the American Radio Relay League
>> (ARRL), at their website:
>>
>> http://www.arrl.org/
>>
>> Bill Horne
>> Temporary Moderator
>>
>> (Please put [Telecom] at the end of your subject line,
>> or I may never see your post! Thanks!)
>>
>>
>
> Three RFI stories come to mind. In my case every time I'd key down on 2m
> I'd obliterate cable channel 18. I was running minimal power when it
> happened too. Turns out that Cox at the time wasn't properly grounding
> their drops. Ooops.
>
> Then of course drive through a parking lot and key up on 2m and you'd
> set off every TRW built alarm system.
>
> But the best is one that happened to a friend. He played on HF quite a
> bit but being the city, he was < 20 feet from the neighbor. It used to
> absolutely trash the neighbors TV, phones, etc.
>
> Finally one day I negotiated the peace between them.
>
> I Explained how to trap the TV RFI but found out why the neighbor was so
> upset. He was a sales rep for Keebler and he had to transmit his orders
> via a Telxon unit connected to the phone. When my buddy was operating it
> would kill the transmission. I also got my buddy to agree to an RF quiet
> time between 6PM and 7PM. That seemed to keep the peace until my buddy
> moved out for greener pastures.
>
> ***** Moderator's Note *****
>
> My first rig was on six meters, and I was, to put it mildly, popular
> with the neighbors ;-). Of course, this was in the sixties, before
> cable TV, when most people still used rabbit ears and TV front-ends
> were as broad as a barn door, but of course a fifteen-year-old kid
> can't say that to an adult who paid a week's salary to hear WA1FXU
> calling "CQ".
>
> Bill Horne
> Temporary Moderator
>
> (Please put [Telecom] at the end of your subject line,
> or I may never see your post! Thanks!)
>
Years ago I would come in on people's TVs and the sort, I would give out
RF filters to take care of the problems until one day a neighbor came to
me and said that his TV service guy told him it was my filter that blew
his TV out. It seems the service guy had messed up the set and wanted to
pass the blame unto someone else, this finally went to Small Claims
court and I won out. That was the last time I ever gave out filters, I
told the people to go down to the nearest electronics store; Radio Shack
was just getting started at that time. One funny side note was that I
used to come into a neighbors electric organ, that was strange and never
could find out why.
--
The Only Good Spammer is a Dead one!! Have you hunted one down today?
(c) 2008 I Kill Spammers, Inc. A Rot In Hell Co.
***** Moderator's Note *****
I don't know if it's still a law, but back then anyone with a tv could
get a filter just by asking the manufacturer for one. I put one on my
family's set, and it cured the problem easily: like you, I wouldn't
give them out or install them, because my dad warned me that I'd have
to fix the sets forever if I did.
Of course, in time I graduated to an Advanced class license, and
started working the "low bands" on SSB. That completely "cured" the
TVI problem: neighbors would complain of interference, but they
couldn't make out the words, and I always told them that they had to
get a callsign before I could help.
Bill Horne
Temporary Moderator
(Please put [Telecom] at the end of your subject line,
or I may never see your post! Thanks!)
| ![[telecom] Re: Cord PBX shown in new TV show](/images/header.jpg)
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