Re: Tesla Coil (RF) radiation range

["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 1/15/02 5:20:54 PM Eastern Standard Time, tesla-at-pupman-dot-com
writes:

>  Let's say your 6 kW coil will light a 40w fluorescent bulb to full
> brightness at 20 ft. This is 40watts. At 40 ft you will have 10 watts,
at 80 ft you will have 2.5 watts, at 160 ft 625 milliwatts, at 240 ft  ~156
milliwatts,  at 480 ft ~39 milliwatts, etc.etc.



>
> It doesn't take 40W of RF power to light a 40W fluorescent bulb.  If it did,
> I'd be mighty worried about safety, because that's a power density of
> several watts per square foot, which is pretty high... (nothing compared to
> the sun at 100W/ft^2, but still a healthy flux)..
>
> Sure, the tube lights up, but it's probably not full brightness.  Bringing
> up an interesting experiment for someone.  Tape a light meter (or a
> photocell) to a fluorescent light.  Put it in the standard fixture fire it
> up and wait for it to come up to temperature.  Measure the brightness.  Now
> do the TC experiment..
>
> I'll bet that the TC is a LOT dimmer than running it off the 60Hz line.  The
> TC has short high power pulses, which create short bright flashes of light.
> Your eye is highly nonlinear, and bright flashes with low duty cycle (with
> low total power) can appear as bright as a much dimmer light with 100% duty
> cycle.  Things with LED indicators make use of this to save power.  The
> other issue is of background lighting.  You can see a fluorescent tube lit
> up (with usual power) in full sunlight.  I doubt this is the case with the
> TC.



I agree. It was an oversimplification intended to show the extreme rate of
dropoff of power from a TC as an RF radiator. What I was showing was that IF a
6 kW coil could light a 40W tube to full brightness, even IF you could get 40W
-at-10 ft, you would only have ~ 30 mw -at- 500 ft. They are actually much poorer
radiators than I indicated. The saber-toothed hypothetical has been slain ! 
:-)
Matt D.