See comment below.
--
J. Mc Laughlin; Michigan U.S.A.
Home:

"Richard Harrison" wrote in message
...
Jim Kelley, AC6XG wrote:
snip

To a first approximation
though, we assume that all the parallel rays intercepted by a dish are
focused on the radiator and aid, adding in-phase. Received carrier power
excites the antenna and this causes a minimum of 50% of this power to be
re-radiated if the antenna is perfectly matched to to the receiver load.
The antenna`s radiation resistance in this case becomes the Thevenin`s
source resistance for the receiver load on the antenna. This requires a
conjugate match between the antenna and receiver input impedances.

----- ... not if one wishes to maximize SNR. Best SNR requires a (slight)
mismatch. Of course, this issue is only significant if SNR is due to the
noise figure (NF) of the receiver and the SNR is small.
73 Mac N8TT