Re: 'MIT/Wireless power/ 50% asserted (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Fri, 08 Jun 2007 14:07:42 -0700
From: Jim Lux <jimlux@xxxxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: 'MIT/Wireless power/ 50% asserted (fwd)

At 12:17 PM 6/8/2007, you wrote:

>---------- Forwarded message ----------
>Date: Fri, 8 Jun 2007 15:18:09 EDT
>From: Mddeming@xxxxxxx
>To: tesla@xxxxxxxxxx
>Subject: Re: 'MIT/Wireless power/ 50% asserted (fwd)
>
>
>Hi Dave, All,
>
>'d like to know how they have a 10 MHz resonator that  produces zero
>radiative energy (losses). A Tesla coil that cannot be  detected by 
>an AM radio at
>more than one wavelength would be very useful in some  areas.
>

At 10 MHz, a 0.5mx0.2m radiator is a very small fraction of a 
wavelength, so it's not a very good antenna.  I haven't run the 
numbers, but radiation might actually be one of the contributors to 
the loss term in their Q.

Bert, having read the original article, could probably shed some 
light on whether they accounted for radiation in their measurements 
of coil losses.

A Q of hundreds for 10MHz is quite respectable, though.


As far as TCs go, they're probably even less efficient than this 
thing, but as far as AM radio detection goes... you can detect very 
small fields with the radio, so even if you only radiate 0.01% of the 
10kW you're dumping into the coil, you're going to hear it a long way 
away.  The spreading loss (1/r^2) is the same for 1 MHz(AM radio) and 
for 14 MHz, and I've radiated a watt (after taking into account 
antenna inefficiency) at 14MHz and been detected thousands of miles 
away.  Yes, at 14 MHz you get skywave, but that just allows a 
practical way to get a 3000 km path to test over.

FWIW 1 wavelength at 1 MHz is 300 meters...