Locating a cellphone jammer...

Mike Deblis · Jan 8, 2004

Just a question...

If you thought that someone in the near vicinity had a cellphone
jammer about their person, how could you simply locate it?

This is in Europe - GSM. These items are illegal for civilian use in
the UK, and I suspect that someone was using one on the train tonight
- for 30 minutes, no-one's cell phone worked in our carriage until we
got to a station, then, like a miracle, they all started working
again. If I moved to the next carriage (about 30mtrs, my phone started
to work again - the signal got better the further I moved from my
original carriage. All networks were effected (O2, Vodaphone, Orange),
so I suspect that it was a jammer being used with a radius of about
15mtrs or so and when the person got off the train at the station,
everything worked. We must have travelled through many cells and
network providers in the 30 minutes, so it certainly wasn't network
downtime...

How could I identify who was using it? I hate the use of cell phones
on trains - but this is more of academic interest...

Thanks

Mike

Ken Taylor · Jan 8, 2004

"Mike Deblis" <mdeblis@hotmail.com> wrote in message
news:bc45f679.0401081324.2e2b209f@posting.google.com...

Just a question...

If you thought that someone in the near vicinity had a cellphone
jammer about their person, how could you simply locate it?

This is in Europe - GSM. These items are illegal for civilian use in
the UK, and I suspect that someone was using one on the train tonight
- for 30 minutes, no-one's cell phone worked in our carriage until we
got to a station, then, like a miracle, they all started working
again. If I moved to the next carriage (about 30mtrs, my phone started
to work again - the signal got better the further I moved from my
original carriage. All networks were effected (O2, Vodaphone, Orange),
so I suspect that it was a jammer being used with a radius of about
15mtrs or so and when the person got off the train at the station,
everything worked. We must have travelled through many cells and
network providers in the 30 minutes, so it certainly wasn't network
downtime...

How could I identify who was using it? I hate the use of cell phones
on trains - but this is more of academic interest...

Thanks

Mike

I'm interested in how the jammer might work, but it may be possible to set
your phone to the 'hidden' (engineering) menu and get the signal strength
and distance-to-cell readings. Either of these may be a good indicator of
the location of the device. Google to see if there are codes available for
getting access to advanced functions on your phone.

Ken

WEBPA · Jan 9, 2004

Just a question...

If you thought that someone in the near vicinity had a cellphone
jammer about their person, how could you simply locate it?

This is in Europe - GSM. These items are illegal for civilian use
i............

Just a thought: Windows on your carriage were different: Metal-evaporated
film for "heat control" which is also a perfect RF blocker for GPS as well as
GSM. Been on the Gatwich Express and seen exactly the same effect (first AM
run: 0515)...no other humans on the carriage. Definetly the glass (which was a
different color.)

Just a thought.....................

webpa

Brian Oakley · Jan 9, 2004

Are these trains underground? Also, could it be possible that the train has
some sort of rf generating device, either via cable or via antenna that
could be interfering? Usually trains communicate in some fashion. If they
have a transmitter on board, if you were located close to the antenna and it
was transmitting "trash" it could very well interfere with your phone.
Brian.

"Mike Deblis" <mdeblis@hotmail.com> wrote in message
news:bc45f679.0401081324.2e2b209f@posting.google.com...

Just a question...

If you thought that someone in the near vicinity had a cellphone
jammer about their person, how could you simply locate it?

This is in Europe - GSM. These items are illegal for civilian use in
the UK, and I suspect that someone was using one on the train tonight
- for 30 minutes, no-one's cell phone worked in our carriage until we
got to a station, then, like a miracle, they all started working
again. If I moved to the next carriage (about 30mtrs, my phone started
to work again - the signal got better the further I moved from my
original carriage. All networks were effected (O2, Vodaphone, Orange),
so I suspect that it was a jammer being used with a radius of about
15mtrs or so and when the person got off the train at the station,
everything worked. We must have travelled through many cells and
network providers in the 30 minutes, so it certainly wasn't network
downtime...

How could I identify who was using it? I hate the use of cell phones
on trains - but this is more of academic interest...

Thanks

Mike

Mike Deblis · Jan 9, 2004

"WEBPA" <webpa@aol.com> wrote in message
news:20040108195132.01759.00001456@mb-m20.aol.com...

Just a question...

If you thought that someone in the near vicinity had a cellphone
jammer about their person, how could you simply locate it?

This is in Europe - GSM. These items are illegal for civilian use
i............

Just a thought: Windows on your carriage were different:
Metal-evaporated
film for "heat control" which is also a perfect RF blocker for GPS as well
as
GSM. Been on the Gatwich Express and seen exactly the same effect (first
AM
run: 0515)...no other humans on the carriage. Definetly the glass (which
was a
different color.)

No - as I mentioned, as soon as we left the first station, everyones 'phone
started working again. There was no "Faraday Cage" effect.

Mike

Mike Deblis · Jan 9, 2004

"Brian Oakley" <brianoakley@ispwest.com> wrote in message
news:btl4aa027o7@enews4.newsguy.com...

Are these trains underground? Also, could it be possible that the train
has
some sort of rf generating device, either via cable or via antenna that
could be interfering? Usually trains communicate in some fashion. If they
have a transmitter on board, if you were located close to the antenna and
it
was transmitting "trash" it could very well interfere with your phone.

I take this train every day, twice a day - have done for years. First time
this effect has been noticed. Its a standard (rather old & crappy)
overground train in the SE of England - last carriage in train, furthest
from the driver's cab..

Also, doesn't explain why as soon as we pulled out of the first station
everyones 'phones started working again.

Mike

Tim Auton · Jan 9, 2004

"Mike Deblis" <mdeblis@hotmail.com> wrote:

"WEBPA" <webpa@aol.com> wrote in message
news:20040108195132.01759.00001456@mb-m20.aol.com...
Just a question...

If you thought that someone in the near vicinity had a cellphone
jammer about their person, how could you simply locate it?

This is in Europe - GSM. These items are illegal for civilian use
i............

Just a thought: Windows on your carriage were different:
Metal-evaporated
film for "heat control" which is also a perfect RF blocker for GPS as well
as
GSM. Been on the Gatwich Express and seen exactly the same effect (first
AM
run: 0515)...no other humans on the carriage. Definetly the glass (which
was a
different color.)

No - as I mentioned, as soon as we left the first station, everyones 'phone
started working again. There was no "Faraday Cage" effect.

Did the train switch from overhead lines to a third rail at the first
station? It could have been RFI generated by part of the train's power
pickup mechanism.

Tim
--
The .sig is dead.

Mike Deblis · Jan 9, 2004

"Tim Auton" <tim.auton@uton.[group sex without the y]> wrote in message
news:brfsvvg1cel84oa2l9tkbkb3df2sp0des5@4ax.com...

No - as I mentioned, as soon as we left the first station, everyones
'phone
started working again. There was no "Faraday Cage" effect.

Did the train switch from overhead lines to a third rail at the first
station? It could have been RFI generated by part of the train's power
pickup mechanism.

There is no over-head cabling on that line - its never happened before in
years of using the line twice every working day - its all "third rail"
power.

Mike

Barry Lennox · Jan 9, 2004

On 8 Jan 2004 13:24:30 -0800, mdeblis@hotmail.com (Mike Deblis) wrote:

Just a question...

If you thought that someone in the near vicinity had a cellphone
jammer about their person, how could you simply locate it?

This is in Europe - GSM. These items are illegal for civilian use in
the UK, and I suspect that someone was using one on the train tonight
- for 30 minutes, no-one's cell phone worked in our carriage until we
got to a station, then, like a miracle, they all started working
again. If I moved to the next carriage (about 30mtrs, my phone started
to work again - the signal got better the further I moved from my
original carriage. All networks were effected (O2, Vodaphone, Orange),
so I suspect that it was a jammer being used with a radius of about
15mtrs or so and when the person got off the train at the station,
everything worked. We must have travelled through many cells and
network providers in the 30 minutes, so it certainly wasn't network
downtime...

How could I identify who was using it? I hate the use of cell phones
on trains - but this is more of academic interest...

You may be able to roughly localise it by walking backwards and
forwards to determine the center of the "dead zone" The jammer should
be somewhere near there. You probably then need a FSM tuned to about
860 MHz, might get you some funny looks on the train however!

Or, perhaps something like an ICOM R1 with an earpiece, you should be
able to hear the jamming signal, and then try to maximise the signal
strength as you walk about.

Barry Lennox

Jerry G. · Jan 9, 2004

Just report the incidence to the phone company technical services. It is
possible at the frequencies that these phones work on, you can have isolated
dead spots.

I am in a high-rise building, and the cell company has an antenna array on
the roof. In this building the cell reception is so bad that the cell
phones are almost unusable. This is because we are under the lobe of the
antenna.

In the town where I live, there are a number of dead spots. I know where a
few of them are. Infact, I know of one that is so acute, I can walk about
50 feet, and the phone is at near zero signal strength on its meter. The
support tech at the phone company told me that they are aware of the
problems, and it would be too expensive for them to fix just to cover a few
thousand square feet where there is not very much cell phone traffic.

I have a feeling you ran in to something like this.

--

Greetings,

Jerry Greenberg GLG Technologies GLG
=========================================
WebPage http://www.zoom-one.com
Electronics http://www.zoom-one.com/electron.htm
=========================================

"Mike Deblis" <mdeblis@hotmail.com> wrote in message
news:bc45f679.0401081324.2e2b209f@posting.google.com...
Just a question...

If you thought that someone in the near vicinity had a cellphone
jammer about their person, how could you simply locate it?

This is in Europe - GSM. These items are illegal for civilian use in
the UK, and I suspect that someone was using one on the train tonight
- for 30 minutes, no-one's cell phone worked in our carriage until we
got to a station, then, like a miracle, they all started working
again. If I moved to the next carriage (about 30mtrs, my phone started
to work again - the signal got better the further I moved from my
original carriage. All networks were effected (O2, Vodaphone, Orange),
so I suspect that it was a jammer being used with a radius of about
15mtrs or so and when the person got off the train at the station,
everything worked. We must have travelled through many cells and
network providers in the 30 minutes, so it certainly wasn't network
downtime...

How could I identify who was using it? I hate the use of cell phones
on trains - but this is more of academic interest...

Thanks

Mike

Jim Thompson · Jan 9, 2004

On Fri, 9 Jan 2004 11:00:38 -0500, "Jerry G." <jerryg50@hotmail.com>
wrote:

Just report the incidence to the phone company technical services. It is
possible at the frequencies that these phones work on, you can have isolated
dead spots.

I am in a high-rise building, and the cell company has an antenna array on
the roof. In this building the cell reception is so bad that the cell
phones are almost unusable. This is because we are under the lobe of the
antenna.

In the town where I live, there are a number of dead spots. I know where a
few of them are. Infact, I know of one that is so acute, I can walk about
50 feet, and the phone is at near zero signal strength on its meter. The
support tech at the phone company told me that they are aware of the
problems, and it would be too expensive for them to fix just to cover a few
thousand square feet where there is not very much cell phone traffic.

I have a feeling you ran in to something like this.

480)460-2350 | |
| E-mail Address at Website Fax

Brian Oakley · Jan 9, 2004

I think youre missing the point. Electronic transmitters get worse with age.
The older they get, the "dirtier" the signal. It could be that the station
you pulled out of has an old transmitter that is creating hash in your phone
band.
B.

"Mike Deblis" <mdeblis@hotmail.com> wrote in message
news:E7rLb.20391$qx2.2275031@stones.force9.net...

"Brian Oakley" <brianoakley@ispwest.com> wrote in message
news:btl4aa027o7@enews4.newsguy.com...
Are these trains underground? Also, could it be possible that the train
has
some sort of rf generating device, either via cable or via antenna that
could be interfering? Usually trains communicate in some fashion. If
they
have a transmitter on board, if you were located close to the antenna
and
it
was transmitting "trash" it could very well interfere with your phone.

I take this train every day, twice a day - have done for years. First time
this effect has been noticed. Its a standard (rather old & crappy)
overground train in the SE of England - last carriage in train, furthest
from the driver's cab..

Also, doesn't explain why as soon as we pulled out of the first station
everyones 'phones started working again.

Mike

Reg Edwards · Jan 9, 2004

What frequency bands do cell phones transmit in?

Paul Burridge · Jan 10, 2004

On Fri, 9 Jan 2004 18:16:18 +0000 (UTC), "Reg Edwards"
<g4fgq.regp@ZZZbtinternet.com> wrote:

What frequency bands do cell phones transmit in?

Most of the stuff I saw on my spectrum analyser was 900Mhz; very, very
narrow-band signals almost like intermittent spikes.

--

My opinion is worth what you've paid for it.

Don Bruder · Jan 10, 2004

In article <btmr5i$man$1@sparta.btinternet.com>,
"Reg Edwards" <g4fgq.regp@ZZZbtinternet.com> wrote:

What frequency bands do cell phones transmit in?

Well, when last I paid attention, US cell-phones did their thing in the
806-899 MHz range. That may have changed in the 8+ years since I paid
attention to details that picky, however, and might be completely wrong
for non-US cell systems.

Back in the days when UHF television channels hadn't yet been pruned to
make room for other things, the top channel (was it 83, or 69? I'm
having a brain-blank episode, and have no references handy) of the TV
set could pull in *SOME* cell-phone signals. Generally, the quality was
crap (Cell phones are operating with a different bandwidth than TV
audio, so this is to be expected) but it WAS possible to listen in on
cell-phone conversations that way. Not long after that was discovered by
the general public, the top 20-ish channels of UHF ceased to be licensed
for TV use, got re-dedicated to something else, and TV makers stopped
making sets that could tune that range.

--
Don Bruder - dakidd@sonic.net <--- Preferred Email - SpamAssassinated.
Hate SPAM? See <http://www.spamassassin.org> for some seriously great info.
I will choose a path that's clear: I will choose Free Will! - N. Peart
Fly trap info pages: <http://www.sonic.net/~dakidd/Horses/FlyTrap/index.html>

Brian Oakley · Jan 10, 2004

It depends on the network and the technology. It can be in the 800 or 1900
MHz range.
Brian

"Reg Edwards" <g4fgq.regp@ZZZbtinternet.com> wrote in message
news:btmr5i$man$1@sparta.btinternet.com...

What frequency bands do cell phones transmit in?

Jerry Greenberg · Jan 10, 2004

From memory, for analog tansmissions it is in the 824.o4 to 893.70 mHz
bands. For the digital network they are in the 1850 to 1990 mHz
bands.

Jerry Greenberg
http://www.zoom-one.com

--

"Reg Edwards" <g4fgq.regp@ZZZbtinternet.com> wrote in message news:<btmr5i$man$1@sparta.btinternet.com>...
> What frequency bands do cell phones transmit in?

Michael A. Terrell · Jan 10, 2004

Don Bruder wrote:

In article <btmr5i$man$1@sparta.btinternet.com>,
"Reg Edwards" <g4fgq.regp@ZZZbtinternet.com> wrote:

What frequency bands do cell phones transmit in?

Well, when last I paid attention, US cell-phones did their thing in the
806-899 MHz range. That may have changed in the 8+ years since I paid
attention to details that picky, however, and might be completely wrong
for non-US cell systems.

Back in the days when UHF television channels hadn't yet been pruned to
make room for other things, the top channel (was it 83, or 69? I'm
having a brain-blank episode, and have no references handy) of the TV
set could pull in *SOME* cell-phone signals. Generally, the quality was
crap (Cell phones are operating with a different bandwidth than TV
audio, so this is to be expected) but it WAS possible to listen in on
cell-phone conversations that way. Not long after that was discovered by
the general public, the top 20-ish channels of UHF ceased to be licensed
for TV use, got re-dedicated to something else, and TV makers stopped
making sets that could tune that range.

--
Don Bruder

US UHF used to go to Ch 83, now it stops at 69

Here is a link to my US TV channel reference chart:

http://home.earthlink.net/~mike.terrell/Refustvoa.html

--
We now return you to our normally scheduled programming.

Take a look at this little cutie! ;-)
http://home.earthlink.net/~mike.terrell/photos.html

Michael A. Terrell
Central Florida

Wim Lewis · Jan 10, 2004

In article <460a833b.0401091655.28dc7ac7@posting.google.com>,
Jerry Greenberg <jerryg50@hotmail.com> wrote:

From memory, for analog tansmissions it is in the 824.o4 to 893.70 mHz
bands. For the digital network they are in the 1850 to 1990 mHz
bands.

Digital modes can use the lower (800MHz) band as well. Individual phones
hunt around for a paging channel they like, and that channel tells them
which other channels are usable for their particular mode.

GSM uses a 200-kHz wide channel and transmits in a 546-usec burst every
4.6 msec. Other systems have other channel spacings and frame rates.

--
Wim Lewis <wiml@hhhh.org>, Seattle, WA, USA. PGP keyID 27F772C1

Wim Ton · Jan 10, 2004

"Reg Edwards" <g4fgq.regp@ZZZbtinternet.com> wrote in message
news:btmr5i$man$1@sparta.btinternet.com...

What frequency bands do cell phones transmit in?

This is a list of GSM frequency allocations sent in by email:

From: http://www.prattfamily.demon.co.uk/mikep/frequency.htm

Mobile phone transmit Base station transmit
Vodafone GSM 900: 890 - 894.6 MHz 935 - 939.6 MHz
BT Cellnet GSM 900: 894.8 - 902 MHz 939.8 - 947 MHz
Vodafone GSM 900: 902 - 910 MHz 947 - 955 MHz
BT Cellnet GSM 900: 910 - 915 MHz 955 - 960 MHz
Vodafone GSM 1800 &
BT Cellnet GSM 1800: 1710 - 1721.5 MHz 1805 - 1816.5 MHz
One2One GSM 1800: 1721.5 - 1751.5 MHz 1816.5 - 1846.5 MHz
Orange GSM 1800: 1751.5 - 1781.5 MHz 1846.5 - 1876.5 MHz

Wim

Locating a cellphone jammer...

Mike Deblis

Guest

Ken Taylor

Guest

WEBPA

Guest

Brian Oakley

Guest

Mike Deblis

Guest

Mike Deblis

Guest

Tim Auton

Guest

Mike Deblis

Guest

Barry Lennox

Guest

Jerry G.

Guest

Jim Thompson

Guest

Brian Oakley

Guest

Reg Edwards

Guest

Paul Burridge

Guest

Don Bruder

Guest

Brian Oakley

Guest

Jerry Greenberg

Guest

Michael A. Terrell

Guest

Wim Lewis

Guest

Wim Ton

Guest

Log in

Welcome to EDABoard.com

Sponsor