wrote in message
...
I'm still playing with the rocket antenna.
The rocket body is a 12 inch diameter aluminum tube.

If I want to put a horzintal dipole on the body I can do one of two
things.


1)Cut an Oval or oblong hole in the skin up near the electronics and
then put in a fibnerglass panel, on that panel I put a cu foil dipole.

How much bigger does the opening around the dipole have to be to not
reduce the efficency of the antenna.

2)I can put a thin dialectric patch on the outside of the rocket and
put the antenna on that.
How thick would a fiberglass dielectric need to be for a good antenna?



I now have a 900Mhz capable bird so I can trim the antenna for minimum
SWR.

This sunday is my last chance to make all of this work so I'm running
out of time.


Paul (Kl7JG)

Since you are considering cutting holes in the body, I would suggest a
vertical slot dipole antenna, which at 900 MHz is 6.25" long -- not sure on
the slot width, but it is lambda/2. A vertical slot has a horizontally
polarized radiation pattern. You may consider 2 or 3 vertical slots fed
from a splitter to ensure complete coverage. This is a similar arrangement
as used by ground based VORs -- a VHF aviation navaid. Radiation directly
below the rocket is at a minimum, as it probably will be with any antenna.

73,

Frank