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 The
patch antenna developed for 436MHz by Greg (VK3BLG) in 2003 is a
remarkable antenna for amateur satellite work. The four element
antenna array has demonstrated about 16dbi gain, a remarkable figure
for its compact size. The truncated cut to the radiating elements
creates the Right Hand Circular (RHC) radiation pattern ideal for
most amateur satellite communication.
Intended
to work as the up link antenna for AO40 my version was only used on
two occasions with excellent results before the demise of AO40 in
early 2004.
I operated the patch array antenna from 2003 to mid 2007 as a
completely steerable array and have been able to consistently manage
contacts through the UO14 and more recently AO51 satellite down to
the horizon with very solid contacts down to 5 degrees above the
horizon. Signal strengths of 5/9 on occasions, but typically 5/5
for most passes.
The main disadvantages of the patch array as I
see it is that it has a very narrow band width, is not easily
adjustable and while not a large problem for satellite work
where the antenna need not be installed in a high and exposed
location is its high wind loading due to the unavoidable large
surface profile.
DIAGRAM
OF SINGLE FEED CIRCULAR POLARISED PATCH ANTENNA (Truncated Corners)
– TOP VIEW
Frequency:
436.0 Mhz
Polarisation:
Right Hand Circular
Patch Material:
2 mm Aluminium
Patch Sides: 316mm (Resonates at 436Mhz)
Patch Height:
17mm above Ground Plane
Patch
Mounting: 6 mm nylon bolts using 3 nuts as spacers 75 mm diagonally
from each patch corner (prior to truncation)
Ground
Plane:
At least 50mm larger all around the patch i.e. for a patch
316 * 316 mm, the Ground Plane should be about
416*416 mm
75
Ohm Point:
0.115 Wavelengths from the centre ( 79.0 mm for 436.0 Mhz)
Truncation: 40.0 mm
Element centre to centre spacing: 0.77 Wavelength or 530mm
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