(Avery Fineman) wrote in message ...
In article ,
(Bill Bowden) writes:

Watson A.Name - 'Watt Sun' wrote in message
...
In article , richard.p.henry@saic
mentioned...

"Tom Sevart" wrote in message
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"WB3FUP (Mike Hall)" wrote in message
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10KV to fire magnetron in counter battery radar. Took six marines to
stop
me from burying my screw driver in the chest of the asshole that
thought
it
would be cute to push the radiate button.

I remember hearing the story of an Air Force tech working on a 30' radar
dish. For some dumb reason, someone energized it and promptly
microwaved
him to death.

Some of these stories are hair rasing... and I'm too much of a weenie to
stick my tongue on a 9V battery...

A Raytheon corporate legend is that one of the engineers discovered the
microwave oven principle when a radar melted a chocolate bar in his shirt
pocket.

When I was in the army at Ft. Monmouth, NJ, we trained on a radar
trainer, had a klystron that put out 1W to the horn on the top of the
unit. We could put our finger over the horn and feel it get mildly
warm from the RF.

Big deal. The Real Thing put our 5 megawatts!

Sure, but the pulse width is only a microsecond, so the
average power is only 5 watts at one pulse per second.
I forget the rep rate of the one I woked on but at
6uS per mile and 400 miles round trip, the rep rate
would be about 400 Hz. So it's 400 times 5, or 2KW.

-Bill

A very rough estimate of "radar range" (time out to return of echo)
is 500 feet per microsecond. For a 200 mile search radar the time
out to echo return is 2+ milliseconds, depending on whether it is
calibrated for statute or nautical miles. Typical PRF for those 200
mile search radars was 400 Hz (PRT of about 2.5 mSec).

Average power output is Peak x ((pulse width)/(repetition time)) or
5 MW divided by 2500 = 2 KW.

2 KW concentrated in a 2 to 5 degree cone can have a devastating
heating effect on human tissue.

One may or may not be "in" the cone of the beam right up close
to the feedhorn but, with the construction of most search radars
(maritime or ground) there isn't much walk-around space to get
away from the feedhorn or the very close in-person effects of
microwave radiation.

When working on HIGH POWER RF at any frequency, believe in
the inverse square law and put as much distance from the antenna
as possible...or have a trusted person down on the power controls
who keeps the thing OFF while up there doing whatever.

I think it would be an interesting subject to compare peak power
RF effects versus average power RF effects. I can't seem to find
much on that in hundreds of pages of medical-biological reports
on the effects of RF radiation on human tissue. Unfortunately,
that has been pretty well shunted aside so that someone can get
their pet "alternate universe" speculations going on in here. :-)

All this gee-whizzy speculation stuff leaves me shocked.
But not fatally so...

Len Anderson
retired (from regular hours) electronic engineer person


There are a few refs and calculations in
http://arXiv.org/pdf/physics/0102007

Lu, et al (referenced) found that peak power was
responsible for spark-gap transmitter injury in rats.

Microwave hearing (referenced somewhat; see a review
Supplement to Radio Science in 1977) also seems to be
because of peak, not average, power.

John

John Michael Williams