OT -RFI question
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I'm getting a Pacemaker installed.
Has anyone heard of RFI issues with Pacemakers? de K2GN - Larry <mailto:[hidden email]> - http://k2gn.com <http://k2gn.com/> K3 S/N - 3278 P3 S/N - 51 LPA500 ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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Suggest you read:
http://www.ce-mag.com/archive/2000/novdec/kimmel.html as a preliminary source. John Ragle -- W1ZI ===== On 5/25/2011 3:35 PM, K2GN wrote: > I'm getting a Pacemaker installed. > > Has anyone heard of RFI issues with Pacemakers? > > > > de K2GN - Larry<mailto:[hidden email]> - http://k2gn.com<http://k2gn.com/> > > > K3 S/N - 3278 P3 S/N - 51 LPA500 > > > > > > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > > > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by K2GN
not RFI heard about here, but certainly magnetism. I know someone with a P/M and they had to be careful about lots of motor type stuff and significantly, security scanners in airports
Suggest you discuss this with your consultant and google it 73 de M0XDF -- Dear God, Did you mean for the giraffe to look like that or was it an accident? -Norma [Children's Letters to God, 1991] On 25 May 2011, at 20:35, K2GN wrote: > I'm getting a Pacemaker installed. > > Has anyone heard of RFI issues with Pacemakers? ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by K2GN
On 5/25/2011 1:35 PM, K2GN wrote: > I'm getting a Pacemaker installed. > > Has anyone heard of RFI issues with Pacemakers? I've seen a ham have rfi problems win a commercial broadcast and two way radio shack. Dunc, W5DC > > > de K2GN - Larry<mailto:[hidden email]> - http://k2gn.com<http://k2gn.com/> > > > K3 S/N - 3278 P3 S/N - 51 LPA500 > > > > > > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by K2GN
I've had a pacer since 1983 (on my fourth one now) and I had a few issues but only with the first one. Primary problem was with corded drill, skilsaw and router rather than ham equipment. The last ones present no noticeable issues.
Bill af4b -----Original Message----- From: K2GN Sent: Wednesday, May 25, 2011 14:35 To: Elecraft Subject: [Elecraft] OT -RFI question I'm getting a Pacemaker installed. Has anyone heard of RFI issues with Pacemakers? de K2GN - Larry <mailto:[hidden email]> - http://k2gn.com <http://k2gn.com/> K3 S/N - 3278 P3 S/N - 51 LPA500 ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by K2GN
Larry I do RFI engineering. Pacemakers are a lot like avionics relative to ham
radio. The working spectrums for pacemakers, avionics, and ham radios are widely separated by both frequency and function. The probability of their mutual interaction is very small. Unfortunately the penalty for even small errors in pacemakers or avionics is very high. The testing is extensive but there is no way one can conceive of all error modes therefore testing will always be incomplete. Also the designers of pacemakers are usually focused on medical function and may miss critical RFI errors. Use your skills learned in ham radio to follow the electronics of your own pacemaker. Pay particular attention to how the doctor adjusts the pacemaker. This is not so you can do your own tweaking. Rather this is to avoid inadvertent ham radio actions that may also effect your pacemaker. Knowledge is your best defense. 73 de Fred, AE6QL ________________________________ From: K2GN <[hidden email]> To: Elecraft <[hidden email]> Sent: Wed, May 25, 2011 12:35:31 PM Subject: [Elecraft] OT -RFI question I'm getting a Pacemaker installed. Has anyone heard of RFI issues with Pacemakers? de K2GN - Larry <mailto:[hidden email]> - http://k2gn.com <http://k2gn.com/> K3 S/N - 3278 P3 S/N - 51 LPA500 ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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On 5/25/11 5:01 PM, FRED TOWNSEND wrote:
> Larry I do RFI engineering. Pacemakers are a lot like avionics relative to ham > radio. The working spectrums for pacemakers, avionics, and ham radios are widely > separated by both frequency and function. The probability of their mutual > interaction is very small. Unfortunately the penalty for even small errors in > pacemakers or avionics is very high. The testing is extensive but there is no > way one can conceive of all error modes therefore testing will always be > incomplete. > > Also the designers of pacemakers are usually focused on medical function and may > miss critical RFI errors. > > Use your skills learned in ham radio to follow the electronics of your own > pacemaker. Pay particular attention to how the doctor adjusts the pacemaker. > This is not so you can do your own tweaking. Rather this is to avoid inadvertent > ham radio actions that may also effect your pacemaker. Knowledge is your best > defense. > > 73 > de Fred, AE6QL > > > > > ________________________________ > From: K2GN<[hidden email]> > To: Elecraft<[hidden email]> > Sent: Wed, May 25, 2011 12:35:31 PM > Subject: [Elecraft] OT -RFI question > > I'm getting a Pacemaker installed. > > Has anyone heard of RFI issues with Pacemakers? > > > > de K2GN - Larry<mailto:[hidden email]> - http://k2gn.com<http://k2gn.com/> > > > K3 S/N - 3278 P3 S/N - 51 LPA500 > > > > > > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Rich, K2 #7115 K3 #5228 ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Fred Townsend
On 5/25/2011 2:01 PM, FRED TOWNSEND wrote:
> Also the designers of pacemakers are usually focused on medical > function and may miss critical RFI errors. The first generation of pacemakers were very susceptible to "audio" rectification. After a great deal of pressure from the FCC and others, they learned how to protect the later pacemaker generations from that. -- 73 de K2ASP - Phil Kane Elecraft K2/100 s/n 5402 ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by M0XDF
Just re-iterating David's advice.
In my former life I worked in a factory. My former boss had to get a pacer and was told specifically to stay away from large magnetic fields. Well, the large, three phase 480V motors used on large machinery like press brakes, shears, and even transformers in production welders put off big magnetic fields while running. The company had the factory tested for magnetic fields to find out how close he could safely get. On the big stuff the limit was 20 feet so that was the limit they set for the entire factory. The company painted 20 foot radius yellow marks on the floor as a reminder for him to stay back. I had to toss him out of my welding booth one day because he got too close. On Wed, 25 May 2011 20:42:05 +0100 "David Ferrington, M0XDF" <[hidden email]> wrote: > not RFI heard about here, but certainly magnetism. I know someone > with a P/M and they had to be careful about lots of motor type stuff > and significantly, security scanners in airports > > Suggest you discuss this with your consultant and google it > 73 de M0XDF -- R. Kevin Stover AC0H ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Fred Townsend
I'm sure Jim Brown will advise you to read his tutorials, but, basically,
keep rf out of the shack. 73 David G3UNA > Larry I do RFI engineering. Pacemakers are a lot like avionics relative to > ham > radio. The working spectrums for pacemakers, avionics, and ham radios are > widely > separated by both frequency and function. The probability of their mutual > interaction is very small. Unfortunately the penalty for even small errors > in > pacemakers or avionics is very high. The testing is extensive but there is > no > way one can conceive of all error modes therefore testing will always be > incomplete. > > Also the designers of pacemakers are usually focused on medical function > and may > miss critical RFI errors. > > Use your skills learned in ham radio to follow the electronics of your own > pacemaker. Pay particular attention to how the doctor adjusts the > pacemaker. > This is not so you can do your own tweaking. Rather this is to avoid > inadvertent > ham radio actions that may also effect your pacemaker. Knowledge is your > best > defense. > > 73 > de Fred, AE6QL > > > > > I'm getting a Pacemaker installed. > > Has anyone heard of RFI issues with Pacemakers? > > > > de K2GN - Larry <mailto:[hidden email]> - http://k2gn.com > <http://k2gn.com/> > > > K3 S/N - 3278 P3 S/N - 51 LPA500 > > > > Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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I called the pace maker company. My wife got one and the literature
specified to not be in the strong fields of radio waves including CB and amateur radio (IMO, the illegal CBers caused most of this interference nightmare with their illegal power and splattering). My wife freaked out. The lady who took the call at the pacemaker company asked intelligent, applicable questions (with my wife also on the phone). I immediately thought she was surprisingly knowledgeable about radio and used all the proper terms. After answering the questions and her giving assurance there would be no problem, I asked her if she was a ham and she gave me her call sign. My wife threw up her hands like all you hams stick together but I reminded her this lady was the expert on her pacemaker and knew what she was talking about. All her answers and explanations matched what I had told her already that it was unlikely with the radios today and being operated properly and legally that it should be just fine. She was very leery for a while and if she thought anything might be happening, she would call me and see if I was transmitting. Nothing ever happened and she is now comfortable that I don't cause her any problems. I run up to 100 watts into attic antennas and legal limit into a vertical about 90 feet from the house. NO PROBLEMS, ever with her pacemaker. 7 years now. Just like the lady said. CALL THEM. Hopefully you will get the intelligent, informed answer instead of the political, CYA answer they print in their documentation. I do have problems with one of my two meter verticals in the attic being about 4 feet from one of the fire alarm wires so when I forget to turn it down below 70 watts on 2 meters FM, the fire alarms go off, then my wife goes off, and I get "reminded" to turn it down. Still happens ocassionally. Happily hamming, 73, de Jim KG0KP ----- Original Message ----- From: "David Cutter" <[hidden email]> To: "Elecraft" <[hidden email]> Sent: Thursday, May 26, 2011 1:31 AM Subject: Re: [Elecraft] OT -RFI question > I'm sure Jim Brown will advise you to read his tutorials, but, basically, > keep rf out of the shack. > > 73 > David > G3UNA > > >> Larry I do RFI engineering. Pacemakers are a lot like avionics relative >> to >> ham >> radio. The working spectrums for pacemakers, avionics, and ham radios are >> widely >> separated by both frequency and function. The probability of their mutual >> interaction is very small. Unfortunately the penalty for even small >> errors >> in >> pacemakers or avionics is very high. The testing is extensive but there >> is >> no >> way one can conceive of all error modes therefore testing will always be >> incomplete. >> >> Also the designers of pacemakers are usually focused on medical function >> and may >> miss critical RFI errors. >> >> Use your skills learned in ham radio to follow the electronics of your >> own >> pacemaker. Pay particular attention to how the doctor adjusts the >> pacemaker. >> This is not so you can do your own tweaking. Rather this is to avoid >> inadvertent >> ham radio actions that may also effect your pacemaker. Knowledge is your >> best >> defense. >> >> 73 >> de Fred, AE6QL >> >> >> > >> I'm getting a Pacemaker installed. >> >> Has anyone heard of RFI issues with Pacemakers? >> >> >> >> de K2GN - Larry <mailto:[hidden email]> - http://k2gn.com >> <http://k2gn.com/> >> >> >> K3 S/N - 3278 P3 S/N - 51 LPA500 >> >> >> >> > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by K2GN
I called the pace maker company. My wife got one and the literature
specified to not be in the strong fields of radio waves including CB and amateur radio (IMO, the illegal CBers caused most of this interference nightmare with their illegal power and splattering). My wife freaked out. The lady who took the call at the pacemaker company asked intelligent, applicable questions (with my wife also on the phone). I immediately thought she was surprisingly knowledgeable about radio and used all the proper terms. After answering the questions and her giving assurance there would be no problem, I asked her if she was a ham and she gave me her call sign. My wife threw up her hands like all you hams stick together but I reminded her this lady was the expert on her pacemaker and knew what she was talking about. All her answers and explanations matched what I had told her already that it was unlikely with the radios today and being operated properly and legally that it should be just fine. She was very leery for a while and if she thought anything might be happening, she would call me and see if I was transmitting. Nothing ever happened and she is now comfortable that I don't cause her any problems. I run up to 100 watts into attic antennas and legal limit into a vertical about 90 feet from the house. NO PROBLEMS, ever with her pacemaker. 7 years now. Just like the lady said. CALL THEM. Hopefully you will get the intelligent, informed answer instead of the political, CYA answer they print in their documentation. I do have problems with one of my two meter verticals in the attic being about 4 feet from one of the fire alarm wires so when I forget to turn it down below 70 watts on 2 meters FM, the fire alarms go off, then my wife goes off, and I get "reminded" to turn it down. Still happens occasionally. Happily hamming, 73, de Jim KG0KP K3 1442, P3 0089 ----- Original Message ----- From: "K2GN" <[hidden email]> To: "Elecraft " <[hidden email]> Sent: Wednesday, May 25, 2011 1:35 PM Subject: [Elecraft] OT -RFI question > I'm getting a Pacemaker installed. > > Has anyone heard of RFI issues with Pacemakers? > > > > de K2GN - Larry <mailto:[hidden email]> - http://k2gn.com > <http://k2gn.com/> > > > K3 S/N - 3278 P3 S/N - 51 LPA500 > > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by K2GN
Thanks for all the great opinions, experiences and web links.
de K2GN - Larry -----Original Message----- From: [hidden email] [mailto:[hidden email]] On Behalf Of K2GN Sent: Wednesday, May 25, 2011 3:36 PM To: Elecraft Subject: [Elecraft] OT -RFI question I'm getting a Pacemaker installed. Has anyone heard of RFI issues with Pacemakers? de K2GN - Larry <mailto:[hidden email]> - http://k2gn.com <http://k2gn.com/> K3 S/N - 3278 P3 S/N - 51 LPA500 ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Fred Townsend
On 5/25/2011 2:01 PM, FRED TOWNSEND wrote:
> Pacemakers are a lot like avionics relative to ham > radio. The working spectrums for pacemakers, avionics, and ham radios are widely > separated by both frequency and function. The probability of their mutual > interaction is very small. Unfortunately the penalty for even small errors in > pacemakers or avionics is very high. The testing is extensive but there is no > way one can conceive of all error modes therefore testing will always be > incomplete. Well said. One of the most difficult hazards to pacemakers is a cell phone used by the person wearing pacemaker -- worst case, it's a 1 watt PEP AM UHF, transmitter within inches of the pacemaker. It's difficult because it's AM, because of the proximity, and also because the wavelengths are short enough that relatively small conductors inside pacemaker can be effective receiving antennas, and relatively small signal loops can provide significant magnetic coupling of near field signals.Strong magnetic fields, like those generated by big transformers and motors, are another serious hazard. Those hazards, and the potentially tragic results of failure, forced pacemaker mfrs to seriously get religion about design and mfg that avoids RFI. Those hazards have all been around for at least a decade, long enough that any modern pacemaker from a serious mfr is almost certain to have excellent immunity to RFI and magnetic fields. If you want to be extra cautious, simply be careful in your home and shack to avoid putting strong magnetic and RF fields around the area where your pacemaker is going to live. That includes placing TX antennas as far away as practical, using effective common mode chokes on transmission lines, using power supplies with transformers that minimize leakage flux, and making sure that there are no wiring errors in your mains power (that is, AC) that set up strong magnetic fields. These wiring errors are discussed in my tutorial about Power and Grounding for Audio and Video Systems, and in the power point about Ham Interfacing. Detailed advice on coax chokes is part of the RFI tutorial for hams. http:audiosystemsgroup.com/publish.htm The RFI tutorial also includes suggestions for clearing the problems with security systems, which are well known RFI dogs. Two common fixes are using twisted pair for all interconnect wiring (CAT5, for example) and using a small capacitor across that wiring at both ends wiring between the sensor and the main unit. In some situations, a ferrite common mode choke may help. 73, Jim Brown K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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As noted by several others the pacemaker industry has indeed recognized the issues surrounding potential interference problems. Most probably remember the issues with microwave ovens - a problem solved over 30 years ago- but you still see the warning signs.
In general, the typical ham does not need to worry about their station causing interference with the pacemaker or implantable defibrillator. They are generally "hardened" to most forms of RF. When I was on the faculty at the University of Oklahoma we established a wireless (cell phones) EMC center and studied the impact on pacemakers: http://www.ou.edu/engineering/emc/Side/Achievments/Research%20Projects/Pacemaker%20Research/Pacemaker%20ResearchHome.dwt A general result was that analog modulation techniques (FM) did not impact the pacemakers. It was the digital modulation modes that caused some problems; all of which have been fixed for many years now. These studies were funded by both the pacemaker companies and the cell phone companies (manufacturers and service providers). Ed, W9EJB |
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On 5/26/2011 1:01 PM, Ed, W9EJB wrote:
> It was the digital modulation modes that caused some > problems; all of which have been fixed for many years now. Note that what you're calling digital modulation is 100% amplitude modulation of a carrier by a series of pulses. For TDMA (time division multiplexing) the duty cycle can be as low as a few percent, so a 50mW cell phone can transmit 1W pulses. Most modern cell phones adjust their TX power as directed by the base station on the basis of their signal strength. Thus, a cell phone close to a cell site may run only 10mW pulses, while one in the far boonies may put out the full 1W (or whatever it's rated/licensed for). It's VERY important to understand this when testing for RFI issues. :) Many (most?) phones can be forced into full power mode for testing. 73, Jim K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Jim Brown-10
On Thu, May 26, 2011 at 12:56 PM, Jim Brown <[hidden email]>wrote:
> ...a cell phone used by the person wearing pacemaker -- worst case, it's a > 1 watt > PEP AM UHF, transmitter... This is interesting. I thought cellphones used an ADC to convert your audio, then some sort of FSK to transmit it. A web search turned up references to NFM used by early analog cellphones, but nothing about AM. Can somebody point me to a relevant link? Tony KT0NY ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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TDMA (time division multiple access) cell phones share a frequency
channel by transmitting only in certain time slots. The power is pulsed on and off even though the modulation mode may be constant-power. Al N1AL On Thu, 2011-05-26 at 15:19 -0500, Tony Estep wrote: > On Thu, May 26, 2011 at 12:56 PM, Jim Brown <[hidden email]>wrote: > > > ...a cell phone used by the person wearing pacemaker -- worst case, it's a > > 1 watt > > PEP AM UHF, transmitter... > > > This is interesting. I thought cellphones used an ADC to convert your audio, > then some sort of FSK to transmit it. A web search turned up references to > NFM used by early analog cellphones, but nothing about AM. Can somebody > point me to a relevant link? > > Tony KT0NY > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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On 5/26/2011 1:30 PM, Alan Bloom wrote:
> TDMA (time division multiple access) cell phones share a frequency > channel by transmitting only in certain time slots. The power is pulsed > on and off even though the modulation mode may be constant-power. Yes. For at least one of the commonly used standards, the repetition rate is about 218 Hz, which puts the harmonics of the detected square waves right in the middle of the audio spectrum, and thus highly audible. Once you know what it sounds like, you will sometimes hear bursts of digital hash at public events, when the cell phone of a public figure gets close to a piece of audio gear with a pin one problem. This used to be a LOT more common than it is now -- mfrs of mics and other audio gear started taking pin one problems and RFI a LOT more seriously when Blackberrys came on the scene bigtime (and reportedly gave a Blackberry to every member of congress and their staff). The senator would lean the Blackberry up against the tube holding the microphone in front of him, and the Blackberry would couple into the mic wiring. It was so bad that they had to shut down hearings until they eventually found and purchased mics without pin one problems. I consulted on that problem, both with the system designer and two mic companies. 73, Jim Brown K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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The major problem with the digital modes (amplitude pulse modes) occured during the initial protocol between the cell & phone. This is a max power mode and occurs prior to phone ringing. The peak powers were as high as 10 watts. Also, during power save modes of TDMA, the packet rate can be as low as 2 Hz. Any rectification in the front end of the pacemakers would see this as a heart rate of 120 beats per minute. This could then inhibit the pacemaker pulses. Fewer than 10% of pacemaker patients are fully dependent for 100% pacing. Therefore brief periods of inhibition would not be noticed by most patients. All observed forms of interference were temporary and never caused microcode corruption or any mode or parameter changes.
All of this was solved by using miniature feedthrough capacitors and became standard industry practice about 20 years ago. Problems solved between cell phones and pacemaker interference. Ed, W9EJB |
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