[amsat-bb] The crossed yagis on the Dayton AO-40 demo station

[Estes Wayne-W10191 <W10191@xxxxxxxxxxxx>]

Tom Busch wrote:

I'm fired up about Cheap Yagi arrays.
I had one comment/observation.  I noticed that the Cheap Yagis mounted on 
Howard's umbrella dish for the AO-40 demo station did not appear to use 
the 17 inch, 72-ohm coax power divider described in the article in CQ-VHF.

So, I guess I'm asking what the phasing harness does, if I'm feeding them 
in phase anyway.


Wayne replies:

My 7x7 Arrow CP yagi uses identical matching as Howard's CP "cheap yagi".  The two planes are physically offset by a quarter wavelength, so there is no "phase shift" section on one side of the Tee.  The 75 Ohm coax connections on each side of the Tee merely match the two 50 Ohm antenna feedpoints to the 50 Ohm feedline.

The "top" of the Tee is about 11 inches long.  I suppose it would be about 17 inches long if a quarter wave phasing section was added.  But that would only be needed if the two antenna planes were NOT physically offset by a quarter wavelength.

Wayne Estes W9AE
Mundelein, IL, USA
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