Re: Halloween Coiling and the FCC

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Mddeming-at-aol-dot-com>

In a message dated 10/3/02 10:25:09 AM Eastern Daylight Time, tesla-at-pupman-dot-com
writes:





>
> Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> <dhmccauley-at-spacecatlighting-dot-com>
>
>
> I know a lot of people here claim that Tesla coils are quite "lousy" at
> being antennas and all that, but they throw a whole huge amount of RF hash
> out in the atmosphere especially when run outside.  Especially in a very
> urbanized area, you may attract the attention of other "listens" especially
> if near an airport, etc...
>
> My very good friend Lou, a seasoned ham operator, made a bet with me.  He
> claimed he could hear my Tesla coil with his antennas at 20 miles away
> during operation.  Since "the group" here previously claimed that Tesla
> coils were lousy radiators, I figured I had that bet won.  Anyways, I set my
> coil up outside and he and my friend were at his house where all his ham
> equipment was set-up.  We then synchronized our watches and he informed me
> to key at random 3 short pulses.  This was accomplished by quickly turning
> off power to my 15kv/60mA NST.  He then told me to do this at random
> intervals for the next half hour and that he would record the exact time he
> received them.
>
> Well, sure enough he got almost all the transmissions.  He also picked up to
> the 3rd harmonics of the signal as well which were much fainter no less, but
> still detectable.
>
> We then reversed roles and repeated the experiment.  Voila.  Same results.
> And it was blatantly obvious when that thing was on.
>
> I never would have thought it could be such an efficient radiator!!!!  I'm
> convinced now!!!!
>
>
> HOWEVER, it still wouldn't stop me from firing my coil up outside.  I'm
> going to do the same.  Of course, Halloween is the perfect excuse to run the
> coil outside!!!!
>
> Dan



Hi Dan,
       It does not surprise me in the least that your coil was "detectable" at
20 miles. You are running 900 W of input power to your coil, and under good
conditions, a 5 to 10 W transmitter should be detectable at 20 miles. He was
using a very sensitive receiver and probably a very directional antenna. The
instantaneous power when you make and break contact is probably several times
your average power rating. There is a big difference between being detectable
and causing unacceptable interference. I think you got suckered on this bet. 
You don't mention if he was receiving you across the spectrum or if he was
tuned to your resonant frequency. You did not mention the time of day or
atmospheric conditions when these tests were done, which can greatly affect the
distance of propagation. When I was in high school, we were sometimes able to
work a station in Jacksonville, Florida from the roof of the school, a 5-story
building in downtown NYC. We were running 50 W and he 60 W. Other times we were
lucky to reach uptown Manhattan from downtown with the same input power.

Matt D.
(A former voice of W2CLE)