In article ,
says...

snippety

I think the degree of work I've done with my van qualifies as
"experienced," so I'll be happy to answer on this. ;-)

When one visits petrol/gas stations here in Australia one sees signs saying
to switch off one's mobile phone as the electromagnetic radiation could
cause a spark and ignite fuel vapour. It has made me wonder how to make APRS
safe so that should you be filling up your car at a gas station you can be
assured that a regular APRS update from your mobile APRS setup won't run a
risk of causing a fire.

The "RF sources causing a spark which causes ignition" is, as far
as I can tell, little more than a modern myth. Static electric discharge
is far more likely to cause ignition than any RF source of the power
levels that amateur or cellular equipment puts out.

For example: You pull up to the pump, get out, start the fuel
going. The biggest and most dangerous mistake you can then possibly
make, especially if you're wearing synthetic-laden clothing and/or
shoes, is to get back in your car to do something, then get back out and
touch the metal of the fuel dispenser handle.

The effect is the exact same thing as scuffing your feet on a
carpet, or getting up out of a synthetic chair, and touching a doorknob.
ZAPP!! With a big enough spark, and enough fuel vapor around the filler
port, you could easily cause a small fire or risk of an explosion.

Best possible thing you can do: Touch the metal body of your car
at least a foot or so away from the filler port BEFORE you touch the
pump dispenser.

Have APRS users considered this possibility and what precaustions, if any,
are taken to deal with this problem?

Well, I make it a point to touch body metal, away from the filler
pipe, before I touch the pump dispenser handle. That, and I make it a
habit of never getting back into the car between the time I start and
stop fueling.

I have also left my own 25-watt APRS transceiver powered and
operational during many fuel stops. Never once did I feel the least
threatened by it, and never once has it caused a problem.

Worry about ESD. It's a far greater threat than any RF source.


--
Dr. Anton Squeegee, Director, Dutch Surrealist Plumbing Institute
(Known to some as Bruce Lane, KC7GR)
kyrrin a/t bluefeathertech d-o=t c&o&m
Motorola Radio Programming & Service Available -
http://www.bluefeathertech.com/rf.html
"Quando Omni Flunkus Moritati" (Red Green)

Then switch it off before you go into the filling station.
And how close to the tanks could one be without switching off?
How about passing the station on the street, possibly with the tank vent
pipes between the street (i.e. yourself) and the pumps?

The major problem you'd have is static electricity. RF will pose no problem in
the normal amounts emitted by a standard mobile rig (i.e., 5-50 wts). The
ignition method most commonly seen is static buildup, person does not discharge
against the car body before touching the nozzle (grounded to the pump via the
hose...it has a wire mesh and/or grounding wire built into it). Nice spark
results, as does ignition of the vapors. One thing that was noted....women
are more likely to have this happen...best guess is due to two reasons. One,
material in clothing may be higher in static-generating capability. Second, on
cold days, women tend to return to the car and wait for the tank to fill. When
they get out, they're a nice static source looking for a ground. The nozzle
provides that.

As for RF, we used to use an old Clegg FM27B to test the electronics (faraday
chamber)....never had any fuel ignition problems, and the lockup problems were
mostly due to ground loop situations which were resonant on some more commonly
used frequency, such as 400 mhz +/-. Drove one prototype unit nuts until the
chief engineer (also a ham) happened to key his 70cm rig when sitting by the
unit. Turns out the local police liked the donuts sold at the station......

A
(ex-R&D/Sales at a pump company)

peter berrett wrote:
Hi all

I have been looking at the use of APRS over packet radio and noted that many
Amateurs now have mobile installations in their cars both for fun and to
assist in tracking the vehicle should it get stolen.

This is quite an appealing idea however I do have one concern that I hope an
experienced mobile APRS user could assist me with.

When one visits petrol/gas stations here in Australia one sees signs saying
to switch off one's mobile phone as the electromagnetic radiation could
cause a spark and ignite fuel vapour. It has made me wonder how to make APRS
safe so that should you be filling up your car at a gas station you can be
assured that a regular APRS update from your mobile APRS setup won't run a
risk of causing a fire.

Have APRS users considered this possibility and what precaustions, if any,
are taken to deal with this problem?

cheers Peter


Urban legend.

See http://www.snopes.com/autos/hazards/gasvapor.asp for a full discussion.


--
Jim Pennino

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