Kyler Laird <lairdkb@mentor.cc.purdue.edu> (04/10/91)
I remember seeing a thread about this a while back. I'd appreciate any info/pointers to info. A friend of mine has a problem with radio reception on his home telephone. The FCC told him to use a choke. That's it!? He hasn't tried this yet, but I'd like to know what his other options are. Also, I'd appreciate knowing the theory behind this. Thanks! kyler
Jeff Sicherman <sichermn@beach.csulb.edu> (04/11/91)
In article <telecom11.283.7@eecs.nwu.edu> Kyler Laird <lairdkb@mentor. cc.purdue.edu> writes: > A friend of mine has a problem with radio reception on his home > telephone. The FCC told him to use a choke. That's it!? He hasn't ^^^^^ > tried this yet, but I'd like to know what his other options are. > Also, I'd appreciate knowing the theory behind this. On the telephone or the manufacturer ? :-) [Moderator's Note: He could also find out where his high-powered and probably illegal CB neighbor is located (if that is the type of radio interference he is getting) and go cut the guy's coax! :) PAT]
herrickd@iccgcc.decnet.ab.com (04/16/91)
In article <telecom11.283.7@eecs.nwu.edu>, lairdkb@mentor.cc.purdue. edu (Kyler Laird) writes: > A friend of mine has a problem with radio reception on his home > telephone. The FCC told him to use a choke. That's it!? He hasn't > tried this yet, but I'd like to know what his other options are. > Also, I'd appreciate knowing the theory behind this. Perhaps the basic idea is to find the person operating the transmitter and choke him. dan herrick herrickd@iccgcc.decnet.ab.com [Moderator's Note: There are all these 'scenarios' people come up with -- red herrings, really -- as excuses for not having Caller ID. From your example above, I take it you would rather force the people to answer the phone every time it rings -- being unable to tell in advance who is calling -- rather than sit down with the people as one parent speaking with another to discuss and correct the misbehavior of your children. PAT]
Joshua_Putnam <josh@happym.wa.com> (04/16/91)
In <telecom11.286.4@eecs.nwu.edu> sichermn@beach.csulb.edu (Jeff Sicherman) writes: > In article <telecom11.283.7@eecs.nwu.edu> Kyler Laird <lairdkb@mentor. > cc.purdue.edu> writes: >> A friend of mine has a problem with radio reception on his home >> telephone. The FCC told him to use a choke. That's it!? He hasn't >> tried this yet, but I'd like to know what his other options are. >> Also, I'd appreciate knowing the theory behind this. > On the telephone or the manufacturer ? :-) > [Moderator's Note: He could also find out where his high-powered and > probably illegal CB neighbor is located (if that is the type of radio > interference he is getting) and go cut the guy's coax! :) PAT] I've never known anyone with CB interference on the phone, but that may just be luck. Here we always have trouble with AM broadcast stations. Depending on the location of the phone lines, quality of the phone, etc., the talk radio can be as loud as the person on the other end of the line, sometimes louder. The only phones that seem to be immune are our old rotary-dial ones from the dark ages. (No touch-tone in my house :-( The stations are all operating legally, and the phone company used to provide specially-modified phones back before customers could buy their own. (The phones have a capacitor soldered across the speaker terminals.) For more serious cases, a phone line filter is available. The Amateur Radio Relay League (ARRL) Handbook, available in any good library, has a detailed section on interference that includes solutions for phone interference and part numbers for the various filters, chokes, capacitors the phone manufacturers use. Josh Putnam josh@happym.wa.com 206/463-9399 ext.102 Happy Man Corp. 4410 SW Pt. Robinson Road Vashon Island, WA 98070-7399 Moderator's Note: If you want to see a place where AM stations make for bad reception on the radio itself, try an area just outside Wheaton, IL where the transmitters for WGN (720 AM) and WBBM (780 AM) are located about a half-mile from each other. When driving within about a mile on any side of those transmitters, you can tune *nothing* on your car radio but them. Solid WGN signal across the whole AM band for quite a distance, then the same from WBBM for awhile. There is a space in the middle of the two where you get only heterodyne from the two of them together. Listen in sometime if you are driving past! PAT]
Nick Sayer <nsayer@uop.uop.edu> (04/22/91)
herrickd@iccgcc.decnet.ab.com writes: > In article <telecom11.283.7@eecs.nwu.edu>, lairdkb@mentor.cc.purdue. > edu (Kyler Laird) writes: >> A friend of mine has a problem with radio reception on his home >> telephone. The FCC told him to use a choke. That's it!? He hasn't >> tried this yet, but I'd like to know what his other options are. >> Also, I'd appreciate knowing the theory behind this. > Perhaps the basic idea is to find the person operating the transmitter > and choke him. Dan just lit my fuse. I am an amateur radio operator and have been on the receiving end of an irate neighbor who had a shoddy "Time Magazine" phone. My transmitter, operating legally, and in total compliance with FCC regulations (and then some!) was blamed by the idiot because, of course, nothing ever went wrong when I was not transmitting. In RFI troubleshooting, being "the cause" and being "at fault" are two different things. It's stupid and irresponsible remarks like Dan's that continue to perpetuate the attitude that force Hams to constantly be on the defensive. Dan owes all of us (450,000 in the United States alone) an appology. Nick Sayer mrapple@quack.sac.ca.us N6QQQ [44.2.1.17] 209-952-5347 (Telebit)
hpa@casbah.acns.nwu.edu (H. Peter Anvin) (04/22/91)
>> A friend of mine has a problem with radio reception on his home >> telephone. The FCC told him to use a choke. That's it!? He hasn't >> tried this yet, but I'd like to know what his other options are. >> Also, I'd appreciate knowing the theory behind this. Well, a "choke" is a fairly simple device consisting mainly of capacitors and inductors and the purpouse of which is to short out the RF radiation before it gets detected in your phone. It can be effective sometimes, and totally worthless at times. > Perhaps the basic idea is to find the person operating the transmitter > and choke him. Aaahh, that is why you can always read in ham radio magazines about angry neighbours coming to the local ham to complain about RFI and TVI (Radio Frequency Interference and TeleVision Interference) BEFORE they even have gotten the transmitter out of the box. Yes, that seems quite common. IDENTITY: Anvin, H. Peter STATUS: Student INTERNET: hpa@casbah.acns.nwu.edu FIDONET: 1:115/989.4 HAM RADIO: N9ITP, SM4TKN RBBSNET: 8:970/101.4 EDITOR OF: The Stillwaters BBS List TEACHING: Swedish
nanook@eskimo.celestial.com (Robert Dinse) (04/23/91)
In article <telecom11.283.7@eecs.nwu.edu>, lairdkb@mentor.cc.purdue. edu (Kyler Laird) writes: > A friend of mine has a problem with radio reception on his home > telephone. The FCC told him to use a choke. That's it!? He hasn't > tried this yet, but I'd like to know what his other options are. > Also, I'd appreciate knowing the theory behind this. I am fortunate enough to live close to a 50 KW AM stations transmitter tower and it has the unfortunate side effect of turning everything into a radio receiver. A couple of .001 capacitors from each side of the line to ground seems to work adequately for getting the RF out of the phone here. But another thing that can complicate the issue, the RF would never be detected and become audio if it weren't for something non-linear playing detector. As it happens, phones generally have clipping diodes across the receiver, the purpose of which is to keep clicks from blowing your ear-drums out, but they also tend to make good RF detectors.
oberman@ptavv.llnl.gov (04/23/91)
In article <telecom11.299.10@eecs.nwu.edu>, hpa@casbah.acns.nwu.edu (H. Peter Anvin) writes: > Well, a "choke" is a fairly simple device consisting mainly of > capacitors and inductors and the purpouse of which is to short out the > RF radiation before it gets detected in your phone. It can be > effective sometimes, and totally worthless at times. Well, a "choke" is not "a fairly simple device consisting mainly of capacitors and inductors". That's a filter, also commonly called a trap. A choke is simply an inductor which is, in turn, simply a coil. Coils work because they present an impedence which increases with frequency. And you want to block RFI while allowing in audio. I'm not familiar with the impedences in telephones, but I suspect that a 10 mH inductor should do the trick. It would present a 63 K impedence at 1 MHz. Frankly a little PI filter made of two chokes and a capacitor would work better, but just a choke will probably do the job. R. Kevin Oberman Lawrence Livermore National Laboratory Internet: oberman@icdc.llnl.gov (415) 422-6955 Disclaimer: Don't take this too seriously. I just like to improve my typing and probably don't really know anything useful about anything. Especially anything gnu.