Re: Singing like a banshee


After reading the message(s) below, I would like to get an opinion about the 
operation of a TC near an airport.  I live within 2 miles of our modest airfield
(Corvallis, OR) and am worried about RF interfering with radio transmissions and
avionics, as well as getting the FCC & FAA on my case.  Aircraft fly directly 
over my house 30% of the time, and we wouldn't want any unwanted visitors from 
______________________________ Reply Separator _________________________________
Subject: Re: Singing like a banshee
Author:  Non-HP-tesla (tesla-at-poodle.pupman-dot-com) at HP-Corvallis,shargw1
Date:    7/16/96 9:25 PM

>From MALCOLM-at-directorate.wnp.ac.nzTue Jul 16 21:52:19 1996 
Date: Wed, 17 Jul 1996 08:28:13 +1200
From: Malcolm Watts <MALCOLM-at-directorate.wnp.ac.nz> 
To: tesla-at-pupman-dot-com
Subject: Re: Singing like a banshee
Hi Chip and all,
                Your comment about modulating coils and the FCC 
caught my eye. I'm afraid I have some bad news.
> When I first started getting into tesla coils, I called the FCC. 
> The guy didn't know much about them, but the one point he made that 
> was clear was that modulating a coil (and thus any output RF waves) 
> is illegal.
All coils emit RF, period. Just how much depends on the quality of 
the ground, size of the coil (length in particular) and power level 
(and probably other factors I haven't thought of as well).
     Secondly, all coils designed to produce sparks can be classified 
as double sideband signal generators, at least when either not 
sparking or producing coronas (no arcs). Ideal quench times reduce 
this to pure carrier but few people ever achieve this and it is near 
impossible to achieve if the system is not arcing to an earthed 
object. Moreover, in an ideally quenched disruptive system, the 
carrier is not a constant amplitude either but a decrementing 
wavetrain (AM in a sense). Additionally, the output, as the secondary 
load is varied and the gap is not optimally quenched, is broadband 
(all over the place - FM).
     Thirdly, disruptive discharge coils (cap and gap) could be 
considered modulated in a sense (the mode effectively being 
interrupted carrier or CW in amateur terms).
    The only saving graces are that we don't hook antennas to them
(although a poor ground can certainly act like one) and we do every- 
thing we can to minimize radiation (want sparks). Those operating 
coils not producing sparks are the worst radiators as can be evidenced 
by lighting fluoro/neon lamps at considerable distances. You can 
achieve the same effect by wandering under a radio mast waving a 
fluoro lamp around.
    Just thought I'd better put this thing in perspective.