[TowerTalk] Active phased arrays.

[Tom Rauch]

>    Yes, you are right about the 1025. And you are correct
in saying that you
> can't get any more patterns out of the array than you
could if you used
> passive components and painstakingly manually adjusted
their values to every
> conceivable useful value.  If you had a circular hex array
of verticals you
> could create a lobe in one direction and make notches in a
number of other
> directions by adjusting all the passive phase shift
networks and the
> complicated combining system.  In order to do that with
mfj-1025s, you would
> need six of them at least and it would take a lot of dial
twiddling to make
> them do what you want them to do.

Actually it would take one 1025 for BSEF  in an eight
element circle array and probably only one or two with a Hex
array. I do that with one delay line in my eight element
system and it can cover 1-5 MHz without adjustment.

But I don't entirely disagree with you, it could be easier
with a memorized pattern. You could synthesize a pattern
that moves a null to almost any direction. How useful that
is is another very lengthy topic.

> towards the signal of interest.  Simultaneously, you are
computing another
> pattern that has a strong lobe on the BPL power lines
nearby with a null in
> the direction of your signal of interest.  You use the
second pattern to
> filter and extract non-coherent noise information and
adaptively use it in
> an LMS algorithm to cancel BPL noise from the first
pattern.

I doubt that is practical at HF receiving random signals.
The phasing system would have no idea what was signal and
what was noise, and you can't have two patterns at once on a
single output port.

You must be talking about an entire receiver chain including
detectors, rather than the system Jim described. In that
case you could sample broadband noise (as long as it wasn't
"hiss") and subtract it out. Of course that involves a
complex receiver chain rather than the complex adaptive
phasing system originally described.

Peaking a near noise floor or below noise floor random
signal (like a weak DX station) is another much more
difficult matter.

Let me know when you get one running!

73 Tom