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Cell Phone Interference
I am wondering what those "hospital approved" phones are that I see. They say regular cell phones cause interference. Is it a scam or true. I do see where cell phone bans are being lifted as findings indicate there is no interference from regular cell phone use.. greg
On May 11, 8:27?am, szeke @pitt.edu (GregS) wrote: > I am wondering what those "hospital approved" phones...
Interference is possible and difficult to perdict in advance. I have not personally seen a "hospital approved" advertised cell phone and would not know what to expect in same. Perhaps there is some other aspect besides RF interference that they are complying with? FYI - There is (was?) a magazine called "Compliance Engineering" that
routinely reported on RF interference to unintentional "receivers". A
classic case is motorized wheel chairs being interfered with by taxi
cab radios. In another case (documented!), a patient died in the
Operating Room because of a P5 or P6 VHF Paging Transmitter located on
the rooftop. Later analysis concluded the paging transmitter was not
malfunctioning and the problem was traced to conducted interference.
(Not all of the O/R Suite equipment was battery operated.)
That said, beware of "spin". I'd be curious to see the ad.
-mpm
-----------------------------------------------Reply-----------------------------------------------
In article <1178888617.470725.59 @w5g2000hsg.googlegroups.com>, mpm <mpmill @aol.com> wrote: >On May 11, 8:27?am, szeke @pitt.edu (GregS) wrote: >> I am wondering what those "hospital approved" phones... >Interference is possible and difficult to perdict in advance.
>I have not personally seen a "hospital approved" advertised cell phone
>and would not know what to expect in same. Perhaps there is some
>other aspect besides RF interference that they are complying with?
These phones are bigger, and yellow and black here. Look more like a portable house phone. >FYI - There is (was?) a magazine called "Compliance Engineering" that >routinely reported on RF interference to unintentional "receivers". A >classic case is motorized wheel chairs being interfered with by taxi >cab radios. In another case (documented!), a patient died in the >Operating Room because of a P5 or P6 VHF Paging Transmitter located on >the rooftop. Later analysis concluded the paging transmitter was not >malfunctioning and the problem was traced to conducted interference. >(Not all of the O/R Suite equipment was battery operated.) >That said, beware of "spin". I'd be curious to see the ad.
>-mpm
By the way, I wish they made some SMALL portable house phones. I'll try to search for those hospital phones some more.
There is an area here where they put up signs warning of any RF device.
The manufacturer of some very important equipment made that suggestion
after failure of said important system. Seems like they need a better design.
greg
-----------------------------------------------Reply-----------------------------------------------
In article <1178888617.470725.59 @w5g2000hsg.googlegroups.com>, mpm <mpmill @aol.com> wrote: >On May 11, 8:27?am, szeke @pitt.edu (GregS) wrote: >> I am wondering what those "hospital approved" phones... >Interference is possible and difficult to perdict in advance.
>I have not personally seen a "hospital approved" advertised cell phone
>and would not know what to expect in same. Perhaps there is some
>other aspect besides RF interference that they are complying with?
>FYI - There is (was?) a magazine called "Compliance Engineering" that
>routinely reported on RF interference to unintentional "receivers". A
>classic case is motorized wheel chairs being interfered with by taxi
>cab radios. In another case (documented!), a patient died in the
>Operating Room because of a P5 or P6 VHF Paging Transmitter located on
>the rooftop. Later analysis concluded the paging transmitter was not
>malfunctioning and the problem was traced to conducted interference.
>(Not all of the O/R Suite equipment was battery operated.)
>That said, beware of "spin". I'd be curious to see the ad.
>-mpm
A long while back, a researcher requested the pager antenna be moved from his room area. The antenna was probably about 25 feet away. It obviously made some interference. I have known cars to malfunction driving near a TV tower. Seems like things are much better. On a British TV show they zapped a car with artificial lightning, and it did OK. greg
-----------------------------------------------Reply-----------------------------------------------
In article <f21nen$a4 @usenet01.srv.cis.pitt.edu>, szeke @pitt.edu (GregS) wrote: >I am wondering what those "hospital approved" phones are that I see. They >say regular cell phones cause interference. Is it a scam or true. I >do see where cell phone bans are being lifted as findings indicate there >is no interference from regular cell phone use.. I did find some info. There appears to be very similar to portable cell phones, but the power level appears to be 100 mw or less. Phones by Spectralink
greg
-----------------------------------------------Reply-----------------------------------------------
"mpm" <mpmill @aol.com> wrote in message ... > A
> classic case is motorized wheel chairs being interfered with by taxi
> cab radios.
There was a lecture hall in college in a building adjacent to a main thoroughfare. The wireless microphone system in the room would pick up the taxi cabs if they keyed up just as they whizzed by... :-) -----------------------------------------------Reply-----------------------------------------------
In article <13497r67binm @corp.supernews.com>, "Joel Kolstad" <JKolstad71HatesS @yahoo.com> wrote: >"mpm" <mpmill @aol.com> wrote in message > news:1178888617.470725.59110@w5g2000hsg.googlegroups.com... >> A >> classic case is motorized wheel chairs being interfered with by taxi >> cab radios. >There was a lecture hall in college in a building adjacent to a main
>thoroughfare. The wireless microphone system in the room would pick up the
>taxi cabs if they keyed up just as they whizzed by... :-)
Back in high school days, there was this Ham opperator, a woman, using 1000 watts on 6 meters, on the military freqs, well she was heard for miles around, I think it was every Sunday night. Everybody used outside antennas back then. Gracy K3JTH greg
-----------------------------------------------Reply-----------------------------------------------
On Fri, 11 May 2007 18:15:30 +0000, GregS wrote: > In article <13497r67binm @corp.supernews.com>, "Joel Kolstad" <JKolstad71HatesS @yahoo.com> wrote: >>"mpm" <mpmill @aol.com> wrote in message >>> A >>> classic case is motorized wheel chairs being interfered with by taxi >>> cab radios. >>There was a lecture hall in college in a building adjacent to a main
>>thoroughfare. The wireless microphone system in the room would pick up the
>>taxi cabs if they keyed up just as they whizzed by... :-)
> Back in high school days, there was this
> Ham opperator, a woman, using 1000 watts on 6 meters, on the military
> freqs, well she was heard for miles around, I think it was every Sunday night.
> Everybody used outside antennas back then.
Did anybody talk to her about it? Usually, hams are very concerned with interference - I've even heard of hams who, when their neighbors complained about picking him up on their TVs, _GAVE_ them filters to filter his signal out of their cheap TV front ends, and came over and installed them! Cheers!
Rich
-----------------------------------------------Reply-----------------------------------------------
In article <pan.2007.05.11.20.17.53.200 @example.net>, Rich Grise <r @example.net> wrote: >On Fri, 11 May 2007 18:15:30 +0000, GregS wrote: >> In article <13497r67binm @corp.supernews.com>, "Joel Kolstad" > <JKolstad71HatesS @yahoo.com> wrote: >>>"mpm" <mpmill @aol.com> wrote in message >>>> A
>>>> classic case is motorized wheel chairs being interfered with by taxi
>>>> cab radios.
>>>There was a lecture hall in college in a building adjacent to a main
>>>thoroughfare. The wireless microphone system in the room would pick up the
>>>taxi cabs if they keyed up just as they whizzed by... :-)
>> Back in high school days, there was this
>> Ham opperator, a woman, using 1000 watts on 6 meters, on the military
>> freqs, well she was heard for miles around, I think it was every Sunday
> night.
>> Everybody used outside antennas back then.
>Did anybody talk to her about it? Usually, hams are very concerned with
>interference - I've even heard of hams who, when their neighbors
>complained about picking him up on their TVs, _GAVE_ them filters to
>filter his signal out of their cheap TV front ends, and came over and
>installed them!
Don't remember exactly, but her affiliation as a Mars radio station probably gave her some immunity. U.S. ARMY MILITARY AFFILIATE RADIO SYSTEM greg
-----------------------------------------------Reply-----------------------------------------------
I wasn't going to bring up all the weird things I've seen (I used to have a high-profile job dealing with lots of towers in the US)... I recall one episode where a music teacher was teaching students on
her piano.
She called in complaining she could hear music coming out of her
piano. (Duh!??)
(At first, I couldn't figure out what she was talking about until it
dawned on me she had a digital piano!) Of course, she was in a
blanketing contour and the audio she was hearing was coming from an FM
on the tower. I don't think the station ever resolved the problem.
She was late reporting it, and they were under no legal obligation.
(This was from an FM upgrade in power)
Another guy swore up and down our tower was causing interference to
his TV reception. (The tower was completly empty - no tenants - no
antennas!!) I asked him to send me a video of the interference.
After which, I suggested he call the local power company and get the
pole transformer replaced! (That fixed it.) I understand this is a
big problem with low-band hams, like broadband over power lines
promises to be...?.
And then you have the truly weird ones...
A paging operator calls me up and says they can't receive a GPS signal
at the tower.
(Which is unusual to say the least. ...weird because there's clear
view of the sky and this particular complaint had "never" came in
before. (Trust me, we heard 'em all.) And besides, you could pretty
much guarantee the GPS satellites were working!) But the tech swore
it was "us".
Sure enough, a low-power TV station on an adjacent tower had removed
their 2nd harmonic filter. I forget exactly which channel, 47 I
think? (We didn't own the station.)
Reinstall filter, slap engineer on wrist, "Don't do that again!".
Problem solved.
Next time, I'll tell you about the kitchen sink (actually a metal
frame base slop sink) at an AM station that was causing interference
200 miles away! We were really lucky to find that one. Had been
going on intermittently for years. I didn't find it myself, but I
understood the problem was so unbelievable (and yet definitely
repeatable), that the whole sink was unbolted, packed up and shipped
off to the engineer in charge at the affected FCC monitoring point.
True story.
So "Yeah", if someone tells me they have a "Hospital Approved" cell
phone, I'll listen.
If a bit skeptical. -mpm
-----------------------------------------------Reply-----------------------------------------------
On May 11, 4:24?pm, mpm <mpmill @aol.com> wrote: > I wasn't going to bring up all the weird things I've seen (I used to
> have a high-profile job dealing with lots of towers in the US)...
...OK just one more, 'cause this one is just too damned funny!! Customer calls in saying the shelter is "nuclear hot" inside. Air
conditioner is running, but not blowing cold.
So we get out there to find an old, busted A/C compressor.
We get that replaced, and about a month later someone else calls in
with the same complaint.
This time though, it looked like some livestock had kicked or knocked
over the compressor. This was at an AM station, which are notorious
for lack of metal fencing. So we built a nice, solid wooden fence
around the (now new) compressor. If you're counting, this is
Compressor #2.
Several weeks go by and sure enough, the call comes in again.
Only this time, the tech on the other end says the wooden fence is all
busted up and he's actually witnessing a bull HUMPING the A/C
compressor!!!
Needless to say, compressor #3 went on the roof !!
-mpm
-----------------------------------------------Reply-----------------------------------------------
On Fri, 11 May 2007 19:52:07 +0000, GregS wrote: > In article <pan.2007.05.11.20.17.53.200 @example.net>, Rich Grise <r @example.net> wrote: >>On Fri, 11 May 2007 18:15:30 +0000, GregS wrote: >>> Ham opperator, a woman, using 1000 watts on 6 meters, on the military >>> freqs, well she was heard for miles around, I think it was every Sunday >> night. >>> Everybody used outside antennas back then. >>Did anybody talk to her about it? Usually, hams are very concerned with
>>interference - I've even heard of hams who, when their neighbors
>>complained about picking him up on their TVs, _GAVE_ them filters to
>>filter his signal out of their cheap TV front ends, and came over and
>>installed them!
> Don't remember exactly, but her affiliation as a Mars radio station probably
> gave her some immunity.
It shouldn't, but then again, I've taken note of your earlier comment, "on the military freqs" - if it was actual military stuff, they probably just didn't give a shit. Thanks,
Rich
-----------------------------------------------Reply-----------------------------------------------
GregS wrote: > In article <1178888617.470725.59 @w5g2000hsg.googlegroups.com>, mpm > <mpmill @aol.com> wrote: >>On May 11, 8:27?am, szeke @pitt.edu (GregS) wrote: >>> I am wondering what those "hospital approved" phones... >>Interference is possible and difficult to perdict in advance.
>>I have not personally seen a "hospital approved" advertised cell phone
>>and would not know what to expect in same. Perhaps there is some
>>other aspect besides RF interference that they are complying with?
> These phones are bigger, and yellow and black here.
> Look more like a portable house phone.
>>FYI - There is (was?) a magazine called "Compliance Engineering" that
>>routinely reported on RF interference to unintentional "receivers". A
>>classic case is motorized wheel chairs being interfered with by taxi
>>cab radios. In another case (documented!), a patient died in the
>>Operating Room because of a P5 or P6 VHF Paging Transmitter located on
>>the rooftop. Later analysis concluded the paging transmitter was not
>>malfunctioning and the problem was traced to conducted interference.
>>(Not all of the O/R Suite equipment was battery operated.)
>>That said, beware of "spin". I'd be curious to see the ad.
>>-mpm
> By the way, I wish they made some SMALL portable house phones.
> I'll try to search for those hospital phones some more.
> There is an area here where they put up signs warning of any RF device.
> The manufacturer of some very important equipment made that suggestion
> after failure of said important system. Seems like they need a better
> design.
> greg
That is also the the way legisltion and regulation also read; if your gizmo is important, it had better be hard to interfere with. Just the same incorrect installation may ruin everything. -- JosephKK Gegen dummheit kampfen die Gotter Selbst, vergebens. --Schiller -----------------------------------------------Reply-----------------------------------------------
GregS wrote: > I am wondering what those "hospital approved" phones are that I see. They
> say regular cell phones cause interference. Is it a scam or true. I
> do see where cell phone bans are being lifted as findings indicate there
> is no interference from regular cell phone use..
Scam? I doubt it. I can pick up GSM cell phones signaling over FM radios from several yards distance. --
Paul Hovnanian mailto:P@Hovnanian.com
------------------------------------------------------------------
SHIFT TO THE LEFT! SHIFT TO THE RIGHT!
POP UP, PUSH DOWN, BYTE, BYTE, BYTE!
-----------------------------------------------Reply-----------------------------------------------
On May 11, 9:03 am, mpm <mpmill @aol.com> wrote:
> On May 11, 8:27?am, szeke @pitt.edu (GregS) wrote: > > I am wondering what those "hospital approved" phones...
> Interference is possible and difficult to perdict in advance.
> I have not personally seen a "hospital approved" advertised cell phone
> and would not know what to expect in same. Perhaps there is some
> other aspect besides RF interference that they are complying with?
> FYI - There is (was?) a magazine called "Compliance Engineering" that
> routinely reported on RF interference to unintentional "receivers". A
> classic case is motorized wheel chairs being interfered with by taxi
> cab radios. In another case (documented!), a patient died in the
> Operating Room because of a P5 or P6 VHF Paging Transmitter located on
> the rooftop. Later analysis concluded the paging transmitter was not
> malfunctioning and the problem was traced to conducted interference.
> (Not all of the O/R Suite equipment was battery operated.)
> That said, beware of "spin". I'd be curious to see the ad.
> -mpm
Used to entertain myself with the 900 mhz radio and teenagers' cheap radar detectors back when I was driving a cab. Hitting the talk button lit up their detectors. Always good for a chuckle when they slammed on their brakes at 80 mph. -----------------------------------------------Reply-----------------------------------------------
Paul Hovnanian P.E. wrote: > GregS wrote: >> I am wondering what those "hospital approved" phones are that I see. They
>> say regular cell phones cause interference. Is it a scam or true. I
>> do see where cell phone bans are being lifted as findings indicate there
>> is no interference from regular cell phone use..
> Scam? I doubt it. I can pick up GSM cell phones signaling over FM radios
> from several yards distance.
Then it is, by definition, a poorly designed radio receiver. Being disrupted by relatively moderate emissions at 8 or 19 times the normal receiver operating frequency is clearly an inferior design. -- JosephKK Gegen dummheit kampfen die Gotter Selbst, vergebens. --Schiller -----------------------------------------------Reply-----------------------------------------------
> Scam? I doubt it. I can pick up GSM cell phones signaling over FM radios
> from several yards distance.
The cellphone here is the prime suspect for a weird thumping the TV set is doing occasionaly (sounds like its power supply does something, several thumps over 3-4 seconds, once a day or so if the phone is at the TV's table). I don't have the statistics on that so I could not swear it is the cellphone, but it has not done it for a week or two since the phone is not put there and it has never done it before without the phone there. What would the phone transmit once a day or so I don't know. It does not interfere with the TV during normal communication, this must be talking to some more remote location. Losing the local station shortly and trying to get in touch with another? Transmitting compressed data it has gathered over the day? Anyones guess :-). Dimiter
------------------------------------------------------
Dimiter Popoff Transgalactic Instruments
http://www.tgi-sci.com
------------------------------------------------------
On May 13, 11:41 pm, "Paul Hovnanian P.E." <p@hovnanian.com> wrote:
> GregS wrote: > > I am wondering what those "hospital approved" phones are that I see. They
> > say regular cell phones cause interference. Is it a scam or true. I
> > do see where cell phone bans are being lifted as findings indicate there
> > is no interference from regular cell phone use..
> Scam? I doubt it. I can pick up GSM cell phones signaling over FM radios
> from several yards distance.
> --
> Paul Hovnanian mailto:P@Hovnanian.com
> ------------------------------------------------------------------
> SHIFT TO THE LEFT! SHIFT TO THE RIGHT!
> POP UP, PUSH DOWN, BYTE, BYTE, BYTE!
On May 14, 8:09?am, Didi <d @tgi-sci.com> wrote: > > Scam? I doubt it. I can pick up GSM cell phones signaling over FM radios > > from several yards distance. > The cellphone here is the prime suspect for a weird thumping the
> TV set is doing occasionaly...
Typical cell phones are in communication with the base station even when you are not using the phone for conversation. This is how the cell phone company "knows" which cell you're on in case you are moving. (They do not ring every cell tower in the world. That would be a waste of spectrum.) There are "channels" for signalling, and "channels" for voice
communications.
If nothing changes, your cell phone might stay on a single signalling
"channel" for weeks.
But...
If your phone experiences a fade, or loss of signal, the reacquisition
may occur on another signalling "channel". (This can, and does, often
happen many times a day.) It can also happen if the cell site
transmitter drops the channel, or if they dynamically reallocate
spectrum to deal with cell site congestion issues, etc...
The point is, when your cell phone (lying peacefully on the TV table)
needs to get updated, it will broadcast a short burst of data back to
the serving cell site. This is probably what you are experiencing (TV
Interference) when the phone is not in Communication.
To extend this reasoning, when you are talking on the phone, First,
you are using a different "channel". One other than the Signalling
"channel", but very likely in the same general band. But many things
have changed. The orientation to the TV for one thing. (Presumably
you are further away unless you put your ear on the TV table?) Also,
the cell site may have instructed the cell phone to reduce output
power on the voice channel, etc...
Unintentional receivers in close proxmity to cell phones and the like
are usually bombarded with fairly high RF signal strengths, which
their front ends were not designed to deal with. While it is
certainly possible to make receivers that would be immune to this
proximity effect, it is not often economical, and may impose physical
size restrictions (for the front end filtering) which consumers could
find objectionable. In short, you just have to live with it.
BTW, I offset the word "channels" in quotes because in the strictest
sense, not all cellular systems (air interface standards) use discrete
channalized bandwidth, but the intent should be clear from the above.
-mpm
-----------------------------------------------Reply-----------------------------------------------
On May 14, 5:09?am, joseph2k <quiettechb @yahoo.com> wrote:
> Paul Hovnanian P.E. wrote: > > GregS wrote: > >> I am wondering what those "hospital approved" phones are that I see. They
> >> say regular cell phones cause interference. Is it a scam or true. I
> >> do see where cell phone bans are being lifted as findings indicate there
> >> is no interference from regular cell phone use..
> > Scam? I doubt it. I can pick up GSM cell phones signaling over FM radios
> > from several yards distance.
> Then it is, by definition, a poorly designed radio receiver. ?Being
> disrupted by relatively moderate emissions at 8 or 19 times the normal
> receiver operating frequency is clearly an inferior design.
> --
> ?JosephKK
> ?Gegen dummheit kampfen die Gotter Selbst, vergebens.??
> ? --Schiller
Probably front end overload, or direct radiation in the receiver IF sections. -----------------------------------------------Reply-----------------------------------------------
Thanks for your cellphone behaviour analysis. > It can also happen if the cell site transmitter drops the channel,
that's a viable guess, could be the cellphone is trying to talk louder to reach some more distant station. I have not watched its reported signal strength when this happens, I may still do it. Could also be many other things, of course. > or if they dynamically reallocate spectrum to deal with cell site
> congestion issues, etc...
Quite unlikely, the area is not densely populated and it also happens during the night when most people are asleep. > The orientation to the TV for one thing. (Presumably
> you are further away unless you put your ear on the TV table?)
No, this can be ruled out. When the phone gets messages and is at that table there is no interference. I doubt it uses a different power level to acknowledge messages. Also, it does not drive the TV mad when it rings. > Unintentional receivers in close proxmity to cell phones and the like
> are usually bombarded with fairly high RF signal strengths, which
> their front ends were not designed to deal with.
It is not the front end. It is, like I said, the TV power supply (switched). The thing (the whole TV set thumping madly) happens even when the power is "off" (on enough to see the remote control and to be messed up by the phone), the signal power from the phone must be orders of magnitude higher than it is during normal transmission to achieve that. Dimiter
------------------------------------------------------
Dimiter Popoff Transgalactic Instruments
http://www.tgi-sci.com
------------------------------------------------------
On May 14, 6:20 pm, mpm <mpmill@aol.com> wrote:
> On May 14, 8:09?am, Didi <d @tgi-sci.com> wrote: > > > Scam? I doubt it. I can pick up GSM cell phones signaling over FM radios
> > > from several yards distance.
> > The cellphone here is the prime suspect for a weird thumping the
> > TV set is doing occasionaly...
> Typical cell phones are in communication with the base station even
> when you are not using the phone for conversation. This is how the
> cell phone company "knows" which cell you're on in case you are
> moving. (They do not ring every cell tower in the world. That would
> be a waste of spectrum.)
> There are "channels" for signalling, and "channels" for voice
> communications.
> If nothing changes, your cell phone might stay on a single signalling
> "channel" for weeks.
> But...
> If your phone experiences a fade, or loss of signal, the reacquisition
> may occur on another signalling "channel". (This can, and does, often
> happen many times a day.) It can also happen if the cell site
> transmitter drops the channel, or if they dynamically reallocate
> spectrum to deal with cell site congestion issues, etc...
> The point is, when your cell phone (lying peacefully on the TV table)
> needs to get updated, it will broadcast a short burst of data back to
> the serving cell site. This is probably what you are experiencing (TV
> Interference) when the phone is not in Communication.
> To extend this reasoning, when you are talking on the phone, First,
> you are using a different "channel". One other than the Signalling
> "channel", but very likely in the same general band. But many things
> have changed. The orientation to the TV for one thing. (Presumably
> you are further away unless you put your ear on the TV table?) Also,
> the cell site may have instructed the cell phone to reduce output
> power on the voice channel, etc...
> Unintentional receivers in close proxmity to cell phones and the like
> are usually bombarded with fairly high RF signal strengths, which
> their front ends were not designed to deal with. While it is
> certainly possible to make receivers that would be immune to this
> proximity effect, it is not often economical, and may impose physical
> size restrictions (for the front end filtering) which consumers could
> find objectionable. In short, you just have to live with it.
> BTW, I offset the word "channels" in quotes because in the strictest
> sense, not all cellular systems (air interface standards) use discrete
> channalized bandwidth, but the intent should be clear from the above.
> -mpm
On May 14, 12:12?pm, Didi <d @tgi-sci.com> wrote: > Thanks for your cellphone behaviour analysis.
Interesting. Yes. It is possible the TV power supply is being interferred with. However, if this is caused by the cell phone in close proximity, I would certainly expect the behavior to exhibit while the cell phone is ringing. It is unlikely that there is a significant change in cell phone RF
output power, regardless of signalling vs. voice channel. It may
change some, but not enough to matter. (i.e., the difference in
antenna response vs. frequency, etc.. Really, not enough to be
concerned with.)
Perhaps the TV is at fault and it has nothing to do with the cell
phone?
Could be a problem in the TV's power supply, or the power quality of
the branch circuit it is using has a problem. (such as: abnormal
line harmonics, bad neutral, bad grounding or bonding, etc..)
You "might" be able to deduce this by trying to replicate the TV
problem by selectivly turning ON and OFF certain high-drain appliances
in the home, especially those with motors. Air Conditioner, Clothes
Dryer (on high heat), Refrigerator, Hot Water Heater, and/or Hot Tubs,
Pool Pumps, well water pumps, etc... if you happen to have those.
Based on your last reply, I am beginning to think the problem is not
with the cell phone proximity. It just sounds like a coincidence.
(??)
To answer one other question, cell phones do not normally "collect and
periodically retransmit" data back to the cell site. Some do, but
they are very specialized devices. Not your run-of-the-mill consumer
handsets.
-mpm
-----------------------------------------------Reply-----------------------------------------------
In article <1179156037.293499.74 @o5g2000hsb.googlegroups.com>, mpm <mpmill @aol.com> wrote: >On May 14, 8:09?am, Didi <d @tgi-sci.com> wrote: >> > Scam? I doubt it. I can pick up GSM cell phones signaling over FM radios >> > from several yards distance. >> The cellphone here is the prime suspect for a weird thumping the
>> TV set is doing occasionaly...
>Typical cell phones are in communication with the base station even
>when you are not using the phone for conversation. This is how the
>cell phone company "knows" which cell you're on in case you are
>moving. (They do not ring every cell tower in the world. That would
>be a waste of spectrum.)
>There are "channels" for signalling, and "channels" for voice
>communications.
>If nothing changes, your cell phone might stay on a single signalling
>"channel" for weeks.
>But...
>If your phone experiences a fade, or loss of signal, the reacquisition
>may occur on another signalling "channel". (This can, and does, often
>happen many times a day.) It can also happen if the cell site
>transmitter drops the channel, or if they dynamically reallocate
>spectrum to deal with cell site congestion issues, etc...
>The point is, when your cell phone (lying peacefully on the TV table)
>needs to get updated, it will broadcast a short burst of data back to
>the serving cell site. This is probably what you are experiencing (TV
>Interference) when the phone is not in Communication.
>To extend this reasoning, when you are talking on the phone, First,
>you are using a different "channel". One other than the Signalling
>"channel", but very likely in the same general band. But many things
>have changed. The orientation to the TV for one thing. (Presumably
>you are further away unless you put your ear on the TV table?) Also,
>the cell site may have instructed the cell phone to reduce output
>power on the voice channel, etc...
>Unintentional receivers in close proxmity to cell phones and the like
>are usually bombarded with fairly high RF signal strengths, which
>their front ends were not designed to deal with. While it is
>certainly possible to make receivers that would be immune to this
>proximity effect, it is not often economical, and may impose physical
>size restrictions (for the front end filtering) which consumers could
>find objectionable. In short, you just have to live with it.
>BTW, I offset the word "channels" in quotes because in the strictest
>sense, not all cellular systems (air interface standards) use discrete
>channalized bandwidth, but the intent should be clear from the above.
I had a flashing back on one of my older phones. It sensed any RF and flashed, thus i knew when it was transmitting.. My current motor Razr seems to run the battery down real fast at times
when I enter the place where i am currently at, where there is no reception.
It seems to get in some mode where it must be doing a lot of transmitting
where there is no reception. Sounds dumb.
Of course teh cell phone will use full power when its in a poor location, and
can't back off power like in a good location.
greg
-----------------------------------------------Reply-----------------------------------------------
On Sun, 13 May 2007 13:41:42 -0700, "Paul Hovnanian P.E." <p @hovnanian.com> wrote: >GregS wrote: >> I am wondering what those "hospital approved" phones are that I see. They
>> say regular cell phones cause interference. Is it a scam or true. I
>> do see where cell phone bans are being lifted as findings indicate there
>> is no interference from regular cell phone use..
>Scam? I doubt it. I can pick up GSM cell phones signaling over FM radios
>from several yards distance.
And I can easily hear GSM phones signalling if I'm on a normal phone. Or on the car radio as the GSM phone switches between cell-sites There's an interesting collection of real-world EMC problems at
http://www.compliance-club.com/banana_skins.asp
Barry
-----------------------------------------------Reply-----------------------------------------------
> However, if this is caused by the cell phone in close proximity, I
> would certainly expect the behavior to exhibit while the cell phone is
> ringing.
It does, actually. Caught it yesterday, was checking if the caller ID worked and went to the TV to check that as well, it was messing up the TVs SMPS allright. > Perhaps the TV is at fault and it has nothing to do with the cell
> phone?
Hey, I would know that. Would you believe I have twice opened and fixed this (cheap) TV,
once it had a dried electrolythic cap which was mounted too
close to a heating 7805 regulator and once I don't remember
what, after a lightning which had killed the Ethernet controller
(and not the coax PHY buffer...) of my Nukeman, the TV and
the cable modem, got the latter replaced and the other two fixed.
But the case for the cellphone is proved now, anyway. It messes
up the power supply (IIRC the one which makes the 5V stays on
all the time, not sure about the others, I think the sweeps supplies
were off but I am no more than 60% sure of that, lightning event
was a year ago). About 30 cm (1ft) from the board is close enough,
I am not sure the missus will allow me to try any closer (she keeps
the phone in the other corner of the room since it got under
suspicion ....:-).
Dimiter
On May 14, 7:49 pm, mpm <mpmill@aol.com> wrote:
> On May 14, 12:12?pm, Didi <d @tgi-sci.com> wrote: > > Thanks for your cellphone behaviour analysis.
> Interesting.
> Yes. It is possible the TV power supply is being interferred with.
> However, if this is caused by the cell phone in close proximity, I
> would certainly expect the behavior to exhibit while the cell phone is
> ringing.
> It is unlikely that there is a significant change in cell phone RF
> output power, regardless of signalling vs. voice channel. It may
> change some, but not enough to matter. (i.e., the difference in
> antenna response vs. frequency, etc.. Really, not enough to be
> concerned with.)
> Perhaps the TV is at fault and it has nothing to do with the cell
> phone?
> Could be a problem in the TV's power supply, or the power quality of
> the branch circuit it is using has a problem. (such as: abnormal
> line harmonics, bad neutral, bad grounding or bonding, etc..)
> You "might" be able to deduce this by trying to replicate the TV
> problem by selectivly turning ON and OFF certain high-drain appliances
> in the home, especially those with motors. Air Conditioner, Clothes
> Dryer (on high heat), Refrigerator, Hot Water Heater, and/or Hot Tubs,
> Pool Pumps, well water pumps, etc... if you happen to have those.
> Based on your last reply, I am beginning to think the problem is not
> with the cell phone proximity. It just sounds like a coincidence.
> (??)
> To answer one other question, cell phones do not normally "collect and
> periodically retransmit" data back to the cell site. Some do, but
> they are very specialized devices. Not your run-of-the-mill consumer
> handsets.
> -mpm
On May 14, 2:12?pm, szeke @pitt.edu (GregS) wrote: > My current motor Razr seems to run the battery down real fast at times
> when I enter the place where i am currently at, where there is no reception....
Sounds right. When far from the tower, the tower will instruct the cell phone to increase it's output power to improve the signal. (And lower when you're in close to avoid overloading the cell site's receiver multicouplers.) So, if you're in an area of poor coverage, you have at least 2 things eating away at battery life: Temporary signal fades, which drive the need for more frequent
updates, and,
High RF power ouput instructions from the cell site.
-mpm
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