Model Forum / General / Rockets / June 2006

Here's an interesting link for such an antenna structure

http://ndl.ee.ucr.edu/barron.pdf

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
rocket.

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

 http://www.nialloswald.co.uk/gallery/v/Rocketry/UKRA2006/Saturday/adr2I3001.jpg.
html?g2_imageViewsIndex=2

and the video results at

 http://www.hyperspace.org.uk/rocket-video/ukra2006/

Chris

Hey! Haigh-Farr makes good antennas. There are two (2.3 GHZ telemetry)
on the nose of this beast:

http://www.wsmr-history.org/losat.htm

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:
http://www.surplussales.com/RF/RFMicrowaveCir.html

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.