On Sun, 15 Jun 2008 02:41:42 -0700, jpg797 wrote:

On 15 Jun, 01:39, "COLIN LAMB" wrote:
Whoops, I misspelled the website. *It is:

www.microwaveeng.com

Colin Lamb

The CAA made some comments about slot antennas in their study on low
power SSR transponders. See page 9 of:

http://www.caa.co.uk/docs/810/Study%...er%201%202.pdf

It looks, from that, as if the optimum for those of us with glass
fuselages would be a vertical dipole mounted inside the rear fuselage. A
14.5cm dipole sounds small enough to fit fairly easily.

However, I have two questions for the experts, as I don't understand RF
radiation patterns or coax losses.

- my glider (Std Libelle) uses pushrods for the rudder and elevator
linkages. IIRC these run along the bottom of the fuselage. If the
dipole was mounted vertically in the upper part of the fuselage
would the control rods wreck the radiation pattern?

- with transponder in the panel and the antenna behind the oxygen
cylinder mount this would put the antenna at the end of 3 - 3.5m
or co-ax. Would that be an acceptable installation?

I hope I never have to fit a transponder, but I'd like to understand this
type of issue in case it becomes a requirement here or I take the glider
some place where one is needed.


--
martin@ | Martin Gregorie
gregorie. |
org | Zappa fan & glider pilot