Maker Pro
Maker Pro

Cell Phone Interference

G

GregS

Jan 1, 1970
0
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
 
M

mpm

Jan 1, 1970
0
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
 
G

GregS

Jan 1, 1970
0
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
 
G

GregS

Jan 1, 1970
0
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
 
G

GregS

Jan 1, 1970
0
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
 
J

Joel Kolstad

Jan 1, 1970
0
mpm said:
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... :)
 
G

GregS

Jan 1, 1970
0
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
 
R

Rich Grise

Jan 1, 1970
0
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
 
G

GregS

Jan 1, 1970
0
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
 
M

mpm

Jan 1, 1970
0
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
 
M

mpm

Jan 1, 1970
0
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
 
R

Rich Grise

Jan 1, 1970
0
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
 
J

joseph2k

Jan 1, 1970
0
GregS said:
These phones are bigger, and yellow and black here.
Look more like a portable house phone.



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.
 
P

Paul Hovnanian P.E.

Jan 1, 1970
0
GregS said:
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.
 
F

Father Haskell

Jan 1, 1970
0
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.
 
J

joseph2k

Jan 1, 1970
0
Paul said:
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.
 
D

Didi

Jan 1, 1970
0
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
 
M

mpm

Jan 1, 1970
0
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
 
M

mpm

Jan 1, 1970
0
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.

Probably front end overload, or direct radiation in the receiver IF
sections.
 
D

Didi

Jan 1, 1970
0
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
 
Top