[VHFcontesting] 10 ghz tripod mounted Microwave Distance meter. Antenna feed efficiency?

[Patrick Barthelow]

Gentlemen:
I have a matched pair of Tellurometers, military version identical to the
pictures here:
https://www.facebook.com/photo.php?fbid=10204283267071911&set=a.10204279850506499&type=3&theater
10 ghz about 30 milliwatts, I think.  Klystron PA. I am curious about this
simple, what appears to be a 2 element
waveguide to yagi  prime focus feed.  I think from this picture album on FB
you can see the other shots of the Tellurometers.
Mid 60s technology, precision sine wave modulated carrier, and null meter
adjustments for precision distance.
a cm or so,  +/-  a few ppm.  Range is ~ 50km LOS or more.  So the design
would benefit from any optimizations of
the transmitted/received 10 ghz signal.  How efficient, or, inefficient is
that cheap and simple, waveguide-yagi feed?
I can get the dimensions, the distance from the parabola vertex to the yagi
feed, and the dish diameter, if useful.
Also I am looking for any old docs, Army or otherwise, that have full
schematics.  Perhaps stashed somewhere on line.
Here on  the outside data plate:
Federal stock number:  6675 089 8886
Model #99   Contract built by Applied Devices Corp College Pt NY.
Best, 73,   Pat Barthelow AA6EG
apol <apolloeme at gmail.com>loeme at gmail.com