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Re: How many joules --> e.m. waves?



On 4/21/97 Bob Sciamanda wrote:

I find in Reitz, et al, the following result for the amplitude of
the 1/r E field propogating from a sinusoidally driven loop antenna
magnetic dipole like yours:

E(r) = {Io*A*w^2*sin(theta)}/4*Pi*epsilon*c^3*r

Io is the current amplitude; sin(theta) is the directionality factor (try
rotating your loop to see it).

Are you sure it is not cos(theta) which would mean maximum E along the
axis? In any case this signiture is very different from the signiture
of the "transformer effect" suggested by Brian. Thus an experiment for
deciding which effect is dominant shoul be straight forward. Only in
principle, of course; in reality it may take weeks.

Don't under-estimate the sensitivity of (even simple) radio receivers.
The specifications of my (cheap Radio Shack) stereo claim a sensitivity
of 900 microvolts/meter for the AM tuner.

Do you mean that E<0.9 mV/m would be below the noise level? No matter how
sensitive a detector may be it is very hard to recognize a signal which is
below the noise level. By the way, my cheap AM radio was tuned on a station
near 550 KHz while the natural f (for L=0.0028 mH and 3000 pF) is 1.74 MHz.
Tunning the receiver on a station closer to 1.74 MHz would be more logical
but I did not think about this.
Ludwik Kowalski