On Thu, 18 Mar 2004 05:39:21 +0000, Tim Auton
tim.auton@uton.[groupSexWithoutTheY] wrote:

Active8 wrote:
[bombs]
Do you all think that tangos are dumb enough to trigger the bomb
with the ringer or would the detonator answer first and listen for a
DTMF sequence. Hmmm? Achmed the bomb maker gets a wrong number just
as he's connecting the thing.

I very much doubt they bother with DTMF decoders. I mean, how often do
you get a wrong number? I've had about 4 in my life. They'll just
connect the ringer (or vibrate function) to the detonator (with
whatever minimal circuitry in between is required - I've never used a
detonator!) and then only turn the phone on at the last minute.

It's not dumb to design a remote detonation system that requires the
absolute minimum of specialist knowledge and equipment to construct.


Tim

New anti-terrorist weapon = telemarketers. They call everybody. Should wipe
out the bomb makers in about a week.

Dave Head

On 17 Mar 2004 12:02:15 -0800, (John Michael
Williams) wrote:

So, first conclusion: To get even a 1 V spark would take a
wire at least 9 m long, all somehow kept within 1 m of the
transmitter. Thus, it appears it is not feasible to create a
hazardous spark with a CB at a gas station.

I'm not entirely surprised. When CB first took off in the UK about 25
years ago some bright spark (no pun intended) discovered that the then
petrol pump meters could be slowed down by keying-up whilst filling up
and you could get a tank full of juice for a fraction of the price. As
soon as the petrol companies cottoned on to this they put around the
scare story about CBers risking explosions by making use of this scam.
I never bought it, partly because | have a big static problem and
during very dry days I get a massive spark discharge upon closing the
car door. This invariably happens at petrol stations, of course, as it
does everywhere else. I've never been blown up yet.
--

The BBC: Licensed at public expense to spread lies.

Jim Thompson wrote:
I was struck by a thought when I heard the latest Palestinian
terrorist trick is to send a kid through the border with a back-pack
bomb triggered by a cell phone....

The Israelis should get a telemarketer's speed dialer and constantly
dial away... boom... boom... boom...

Not really. The technology is far better.
Here you can get those industial mobiles with a serial
output. You can send an SMS which's string can be decoded by
software of you own microcontroller.

Rene
--
Ing.Buero R.Tschaggelar - http://www.ibrtses.com
& commercial newsgroups - http://www.talkto.net

On Thu, 18 Mar 2004 14:08:26 +0100, the renowned Rene Tschaggelar
wrote:

Jim Thompson wrote:
I was struck by a thought when I heard the latest Palestinian
terrorist trick is to send a kid through the border with a back-pack
bomb triggered by a cell phone....

The Israelis should get a telemarketer's speed dialer and constantly
dial away... boom... boom... boom...

Not really. The technology is far better.
Here you can get those industial mobiles with a serial
output. You can send an SMS which's string can be decoded by
software of you own microcontroller.

One could easily imagine a semi-smart anti-convoy bomb that could be
remotely triggered by a hidden operator to go off after a programmable
delay (with password), so signal jamming would be relatively
ineffective. Nasty, and hobbyist-level technology once you have the
phone.

Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

In message , Guy Macon
writes

[Snipped]

It's silly to worry about cell phones when every car that drives in
has a high-voltage ignition system under the hood, 12V spark-producing
switches in the door frames, and a hot catalytic converter underneath
the car.

The RF/electrical bit seems like a red herring to me, but I suppose it
would be better to give full attention to the flammable liquid you're
pumping rather than a telephone conversation.

--
Syd Rumpo

On Wed, 17 Mar 2004 21:33:43 GMT, Dave Shrader
wrote:

John Michael Williams wrote:

SNIP

However, the first radios transmitted
sparks, so in principle it should be possible to
transmit near a long wire separated by a small gap from
ground or another wire and get a small spark. So, I
decided to try an experiment.

SNIP

There is one other potential source for a spark that you did not
investigate.

A make/break contact in a switch causes sparks when opened. The US
Military specifies special shielded switches for their explosive, gas
vapor, etc., environments.

This reminds me of a story... (pause while room clears out).
Years ago I was an engineering student working for Cadillac
Motor Car. Electronic fuel injection was new then, and there
had been a couple of fires in the field that were suspected to
have been caused by leaky fuel lines, which were at higher
pressure than on the old carbureted cars. There were competing
theories, however, as to what exactly was setting off the fire.
I got assigned to help the guy doing the experiments to find out.

He had a car fitted with a plexiglas hood, topped by a small tower
with a high-speed movie camera pointing down for a good look
at anything happening in the engine compartment. Two fire
extinguishers were arranged to cover the under-hood area,
and a fuel vapor sensor was also installed there. The way
it was supposed to work was that he would drive and I would
operate the hand-pumped sensor, and at the first sign of fire
he would trigger the extinguishers. We ran all the tests
at the GM Proving Grounds in Milford, Michigan.

We tried making leaks in the fuel injection hoses. We had gas
spraying all over under the hood, collecting in pools on the
hot exhaust manifold. We tried poking holes in the spark
plug wire insulation. Nothing, no fire.

Finally I got a bright idea, and loosened the ground for the
air conditioner compressor clutch. The idea was that this
was a big inductor, and if the circuit opened there would
be a big spark. Then all we needed to do was get the
wire to bounce. We tried swerving from side to side,
and driving on bumpy tracks, but no deal. I was *sure*
that this spark would do the job, but we couldn't tell
if we were really getting the spark. So finally I stood on the
hood, holding on to the camera tower, so I could see
for myself if there were sparks. He drove down the
bumpy road one more time, and I did in fact see a spark:
The high-speed movie shows the fire spreading out
from it, more and more on each frame. Also on each
frame was the back of my head, moving away more
and more on each frame, until the extinguishers doused
everything. What a rush!

Them was the good ole' days.....


Bob Masta
dqatechATdaqartaDOTcom

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com

Paul Burridge wrote:
I've never been blown up yet.

You've never died yet, either. :-)
--
73, Cecil http://www.qsl.net/w5dxp



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(John Michael Williams) wrote in message om...

I was just trying to add some factual information to the
link I gave, which was just a lot of rumor--both pro and con
RF hazards. Check it out.

From time to time, I read postings about people complaining
about others gabbing on a cell phone while (self-serve)
refueling.

I don't follow what you say about cross-posting. I'm not a ham
operator, so if I am making some obvious mistake, I thought
adding the antenna group would get a correction. Is that your
interest?

Hopefully, this thread will end up by putting to rest
fears of cell phones around gas stations, at least from the
RF standpoint. Also, if I'm wrong, and there IS danger
from the RF, someone should be able to correct me. Either way,
it's an interesting topic, don't you think?


You may have missed out one thing: did you try this with any resonant
loads? Resonant loads are not so hard to come by at the higher
frequencies.

Another question concerns spillage of gas: if youre yacking away its
much easier to spill fuel. I cant draw any conclusions but one has to
at least look at these factors.


Regards, NT

One thing that may set off a detonator is a RF field with a wavelength in
the order of the detonator leads.

From the time I worked with detonators on oilrigs, an absolute radio-silence
was required till the charge was safely lowered down the borehole.

Wim

On Thu, 18 Mar 2004 10:30:45 GMT, Dave Head wrote:

On Thu, 18 Mar 2004 05:39:21 +0000, Tim Auton
tim.auton@uton.[groupSexWithoutTheY] wrote:

Active8 wrote:
[bombs]
Do you all think that tangos are dumb enough to trigger the bomb
with the ringer or would the detonator answer first and listen for a
DTMF sequence. Hmmm? Achmed the bomb maker gets a wrong number just
as he's connecting the thing.

I very much doubt they bother with DTMF decoders. I mean, how often do
you get a wrong number? I've had about 4 in my life. They'll just
connect the ringer (or vibrate function) to the detonator (with
whatever minimal circuitry in between is required - I've never used a
detonator!) and then only turn the phone on at the last minute.

It's not dumb to design a remote detonation system that requires the
absolute minimum of specialist knowledge and equipment to construct.


Tim

New anti-terrorist weapon = telemarketers. They call everybody. Should wipe
out the bomb makers in about a week.

Dave Head

Not if they're on the Do Not Call list
--
Best Regards,
Mike