[opendtv] Re: MIMO

Ron Economos wrote:

Can't say that I've ever used one. When I was active in
amateur radio satellite communications, I used crossed
Yagi antennas. Either the elements were co-located
and fed out 90 degrees out of phase, or the elements
of one yagi were positioned 1/4 wave ahead/behind
the elements of the other yagi (and both are fed
in-phase).

Here's a picture of a circular polarized yagi using the 1/4
wave offset technique.

http://www.m2inc.com/products/vhf/2m/2mcp14.html

The advantage over the Lindenblad is that it has real gain, where the Lindenblad does not have much.

The disadvantage is that it's directional, so it doesn't work for low-earth-orbit satellites. Those guys need to go by fast to stay in orbit.

I wonder. Can't one connect together four yagis, arranged horizontally 90 degrees apart, and get a high-gain omni antenna for horizontally polarized signals? Paralleled together like the Lindenblad, except the main folded dipole elements of the four yagis would be as close together as possible. Or even stacked.

Depending on specifics, the gain could be fairly even all around.

Bert

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