Jeff Liebermann wrote in message . ..
On Sun, 21 Mar 2004 23:00:47 +0000, John Woodgate
wrote:

I read in sci.electronics.design that Jeff Liebermann
wrote (in c1tr509eqipks7lt08ttt5cvnpkumu
) about 'CB Radios, Cellphones and Gasoline Vapor
Ignition', on Sun, 21 Mar 2004:
I didn't know that it wasn't linear.

Google for Paschen's Law. For high voltages it is linear enough for
calibrated spark gaps to be used as voltmeters in the past. The high-
voltage terminals were open and accessible, giving a whole new meaning
to the phrase 'Paschen killers'.(;-)

Yep. That's it. Thanks. Haven't seen that since kollege. Also saw
your comments on the topic in other usenet news articles. So much for
my simplified view of ionization.

Online spark gap calculator:
http://www.cirris.com/testing/voltage/arc.html

Minimum breakdown voltage in air at STP is about 350VDC. For RF, that
would be:
350 * 0.707 = 192 Vrms
Into a 50 ohm antenna at the coax connector,
P = E^2 / R = 192 * 192 / 50 = 737 watts
for any size spark gap. I don't know of any kilowatt cell phones

Then again, some users seem to be able to put in kilohours of talk.
Does that count? (just kidding).

Seriously, into air at the antenna,

P = E^2/377 ~= 97 W.

A very sharp tip would create an additional gradient,
which suggests trying to spark with a sharpened antenna against
something metallic at AC ground.


around, but that's the power output needed to arc at the antenna
connector. It might be somewhat lower due to the effects of RF vs DC.
Also a suitably weird antenna could be fabricated to dramatically
increase the voltage at some point. However, those coils are usually
up in the air where they cannot get close to a ground suitable for
forming a spark gap.

John

John Michael Williams