Many years ago, when costs were quite different:

The British police used a hybrid system to extend the range of their low
power 400 MHz transceivers. They found some large almost flat roofs located
near the edge of coverage. At the edge of the roof most near to the base
station they erected a high gain antenna pointed at the base station. Coax
was run to a BPF + mixer + narrow BPF + mixer + amplifier where the LO for
both mixers is the same. (This scheme cleans the signal and adds some
amplification.) From the active device, coax was run to the distal edge of
the roof to a second gain antenna pointing to the sector of interest. Both
antennas had grid reflectors/shields so as to reduce to a minimum their
"behind" coupling, which had to be less than the gain added by the active
device.
The scheme worked.

I have used passive schemes where a high gain antenna on a roof captures
signals that are distributed in basements and tunnels through a TL made
deliberately leaky. Have coverage where none was available before.

The sub-theme of Richard is that one needs to calculate the numbers to
see if such systems will work.

73 Mac N8TT

--
J. Mc Laughlin; Michigan U.S.A.
Home:
"Richard Harrison" wrote in message
...
Buck wrote:
"How critical would the matching of those beams have to be?"

Very.

Recall that a perfectl;y matched antenna delivers only 50% of its
received energy to its load. The other 50% is re-radiated. In the case
of back-to-back antennas, the load of one antenna is the other antenna.
The source resistance of one antenna is the antenna resistancce of the
other antenna.

If one antenna is shorted or open, 100% of the energy it receives is
re-radiated.

So if all antennas are in far-fields, and if all antenna connections are
lossless, and if all antennas are properly aligned, and if the match of
all antennas is perfect, overall system gain is the sum of the antenna
gains minus the path losses (both paths with a pair of antennas
back-to-back). Recall that the radiated signal loses 22 dB in the first
wavelength and 6 more dB exery time the distance doubles after that.

Best regards, Richard Harrison, KB5WZI