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# Re: Satellite Builder Question

```I asked about how to calculate field strength given TX power:

On Thu, 8 May 2003, John M. Franke said to See the WEB page:

> http://www.astron.nl/craf/conv.htm

Which explains the relationship between power and field stength is

(P*G)/(4pi*d^2) = (E^2)/(120*pi)   Where G is gain, d is distance

And notice that wavelength does not enter into it.  That is where I was
getting all messed up, because the maximum voltage that can be induced in
a 1 meter length of wire depends on frequency.  But since the question was
not "what voltage will be induced in a wire", but "what is the field
strength", then the above gives the answer without respect to frequency.

Thus, my 2W transmitter on our spacecraft generates 7.7 Volts per meter at
one meter no matter what the frequency.

Thanks to all who responded.

Bob

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