Michael Black wrote:
On Sat, 30 Jan 2016, Allodoxaphobia wrote:

In rec.radio.amateur.antenna, you wrote:
gareth wrote:
One of the problems with beams is the cable winding around
the mast if you try to turn too far in one way or another.

These difficulties have long been solved in the world of radar,
so, has anyone conceived of an infinitely rotatable 50 ohm
coupling for our beam antennae?

Sounds like a $200 solution to a $0.75 problem, i.e. an extra foot or
two of coax to allow slack for turning.

With 4 different yagis on the mast, a large, bundled loop of
coax(es) *HAS* to be The Way To Go.

Yes, radar needed such couplings since the antenna went around 360
degrees, since you wanted to see in all directions.

And I'd like to think they've now moved to "electronically steerable"
arrays for radar, multiple fixed antennas that are switched to the
receiver via diodes or whatever. You see some of that in amateur radio
DF'ing.

Michael

They are called phased arrays; here are two I worked on:

https://en.wikipedia.org/wiki/AN/TPQ...refinder_radar
https://en.wikipedia.org/wiki/AN/TPQ...refinder_radar

These use active electronically scanned arrays.

A discussion of how it works:

https://en.wikipedia.org/wiki/Phased_array

https://en.wikipedia.org/wiki/Active..._scanned_array

Phased arrays are extremely complex and expensive compared to simple
rotating search radars.



--
Jim Pennino