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

[LUDWIK KOWALSKI <kowalskil@alpha.montclair.edu>]

                                    Three questions:
On 22 Apr 1997 Bob Sciamanda wrote:

> Your "rig" is putting out a broad band signal; I don't expect much of a 
> tuning effect over a broad range of the receiver "dial"!

We have a well defined LC circuit with low R. Thus the frequency band of 
the oscillating current is very narrow. Why would the e.m. wave emitted by 
the wire loop have "a broad band"?  

> The E field has a null along the normal to the plane of the coil. 

That was a big surprize to me. For some reason I used to think that the 
NORMAL to a wire loop antenna must be oriented toward the source to maximize
the response from a station (same as for the NORMAL to the dipole TV antenna 
on a roof). If this were correct then shouldn't the power emitted be also 
maximized ALONG THE NORMAL? Does E=0 imply zero power?
 
> Don't under-estimate the sensitivity of (even simple) radio receivers.

Do you really think that a small fraction of 84 pJ (a small fraction of
less than 1e-10 joules !), intercepted by a tiny antenna of a cheap radio 
set, will not be lost below the noise level? Does anybody know what a 
typical noise level of a radio set is, in term of microwatts?
                                                         Ludwik Kowalski