> . . . . Considering the transponder only
>transmits a low duty cycle burst and is receiving most of the time, it's
>probably not a problem. This also would fall under the guidelines for a
>controlled environment, meaning the occupants can be told they are sitting in
>an RF field, and the transmitter can be turned off if so desired. Between
>the low power and intermittent low power transmit, I would be pretty certain
>everybody will be fine. It certainly is an area worth learning a little bit
>about. It's a complex concept, and isn't always fully understood by even the
>experts. I still think getting the antennas as far away from the
occupants is
>a good idea.
>> . . . . . In the prototype we installed it outside the
>> shell, below the passenger seat, and then had the whole area above the
>> composite shell covered with a thin alum sheet to act as the ground plane
>> and to protect the passenger from any radiation. (Remember, I was the
>> one who sat on the passenger side in all those demos). I always wondered
>> how effective the alum sheet was in protecting my body. So far, so good.
Concerns for radiation safety and transponders surface from
time to time in aviation circles . . . especially when some
folk read that certain models of tranpsonders put out "600 Watts".
Flags go up and statements are made to the effect, "Gee, my microwave
oven is only 600 watts and it will really toast things . . ."
The "600 Watt Out" and the "toasty foods" are both true statments
but unrelated to each other. Tranponders are rated for PEAK power
output during the few tens of microseconds/second while replying to
an interrogation. Microwave ovens are rated in CONTINUOUS or
HEATING power output which will indeed "toast things".
A transponder's very low AVERAGE power output, presents no
hazard even at 600 watts peak. Most modern transponders
are rated at only 100 to 200 watts peak . . . the need for big
transmitters has evaporated given improvements in solid
state receiving amplifers used at modern radar sites.
Long and Vari-Ez builders were oft cautioned about shielding
the family jewels from ravages of "tranponsder onslaught"
by lining the seat pan with copper foil. In fact, both the concern
and the practice were unfounded in physics.
Bob . . .
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( Knowing about a thing is different than )
( understanding it. One can know a lot )
( and still understand nothing. )
( C.F. Kettering )
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http://www.aeroelectric.com
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