In fact, for HF, you can probably get away with smaller active
antennas for receive. There's no particular reason why the Tx
antennas and the Rx antennas have to be the same, since you're not
typically receiver noise figure limited.
Adaptive nulling is a bit weird to
work with as a user, especially if you expect to control it. And, for
hams, they want a bit more control.
Using this kind of technology is about the only reason I would trash
my current rigs and go for a custom driver (but it would have to
inhabit each array antenna's amp and thus render it a complete
transmitter. This would in turn cast all the features (like SSB
generation) into each of those elements. The unit cost of this would
climb because of feature creep, not component pricing.
What would be cool is to have a
3D panoramic display that somehow indicates not only the frequency
spectrum, but the angle of arrival.
When living in a residential area, as I do, canceling or reducing local qrm
and man made noise is your first interest!
Using an array is may be the only way to go. Either by using analog means
(phasers) or using digital signal processing. In DSP a lot more is possible.
I use an array of 2 small active loop antennas.
The two phase coherent receivers are made using the front-ends of two
Elecraft K2īs and a Delta 44 soundcard in the PC. The software makes
the rest of the dual (SDR) receiver. No expensive hardware needed.
See:
http://www.pa0sim.nl/Software.htm
(one of the windows shows the phase difference (TDOA), which helps
eg. selecting the correct phase for the phaser)
Even two antennas can be very effective against local qrm and even non
local qrm. I sure would like to try four antennas HI. It is easy to scale it
to four antennas/receivers, but I still have my qrl .....
73 de Jan PA0SIM