While their test setup wasn't too bad they didn't do enough testing.
Radiation patterns are usually tested with a wrap around antenna
installed on the vehicle or at least a representative structure because
the conductive body effects the pattern. In addition you want to take
more than a single roll pattern at 90 degrees. Otherwise you will never
know what the full pattern is like.
In any case it looks like their pattern was hurt by the use of a single
element that didn't go all the way around. Depending on the diameter,
different approaches are possible. From extending the width till it goes
all the way around on smaller diameters to a corporate feed network to
multiple patches on larger diameters.
David W. Schultz
firstname.lastname@example.org (Timothy J. Salo) writes:
Unless you have the money and facilities to work with Taconic or
Rogers Duroid PCB material then forget about it. In any case,
phenolic or QT is quite absorptive at these frequencies and you don't
really want your antenna in close proximity to that. It's pretty easy
to make a fin antenna to work against a groundplane on the body of the
I've had some very good result by just poking a dipole antenna out the
side of the rocket. Yes, it's a bit draggy but the improved video
performance more than makes up for that and it's no barrier to going
very fast. I've done this above Mach 1 at least half a dozen times
with no ill effects.
You can see it sticking out the side of the avionics rig in
and the video results at
MARS Flight Crew http://www.mars.org.uk /
Hey! Haigh-Farr makes good antennas. There are two (2.3 GHZ telemetry)
on the nose of this beast:
I have been wanting to build a GPS antenna but the one thing that is
stopping me at this point is test equipment. I need to be able to test
the antenna to verify/tweak the tuning.
Materials are fairly easy to get from:
You will find it very difficult to add a duroid radome because the
bonding film requires very high pressures and elevated temperatures to
work correctly. But for most applications something less robust than
duroid should work fine.
David W. Schultz
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