[MLB-WIRELESS] Galaxy/Conifer grids

[george]

Just measured mine which comes out at 60mm

george

-----Original Message-----
From: Julian Featherston [mailto:julian at concentrate.com.au]
Sent: Sunday, 17 February 2002 5:48 PM
To: melbwireless at wireless.org.au
Subject: [MLB-WIRELESS] Galaxy/Conifer grids


Hi All

I've just been comparing the grids on the 20" (medium) and the 36"
(large)
These are rectangular aperture, cast magnesium grids with a weathered
grey appearance
The three grids sizes all use the same feed system (318mm focal length)

The curly bit is that all the grids should be segments of the same
parabola, but there not.
The 20" is flatter, (by about 18mm either side) this is very strange.

However it has been found that any grid only needs to be within +/-16mm
(@2400Mhz) of the perfect parabola to be within 1dB of max

I'm pretty sure this 20" grid got flattened at some point.
If someone could measure the depth of another 20" grid that would be
great,
I just removed all bolts and lay it face down so the corners sat on the
floor and measured the maximum height above the floor to be 61mm. (from
floor to the back of the grid)

Current Hills grids also use 3 grid sizes for the same feed. Any
thoughts on weather a rectangular horn feed could be optimised for the
36" that would be better than the standard?


Jules



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