[Paparazzi-devel] 900 Mhz Antenna questions

[Helmut Wabnig]

On Thu, 06 Dec 2007 10:40:18 -0500, you wrote:
>.
>Date: Thu, 6 Dec 2007 07:40:13 -0800 (PST)
>From: Uttam Chandrashekhar <address@hidden>
>Subject: [Paparazzi-devel] 9Xtend and antenna options for 900mhz

>..............
>. We are using the 900mhz 9Xtend Maxstream modules,
> and the standard module comes with a massive dipole antenna. Since we require
> about 3kms range, can I replace this with just a whip antenna? (The radio 
> modem
>at the RX will have the standard dipole antenna). If so, how do I go about 
>adapting
> it to hook onto the Reverse SMA connector? The paparazzi site has some 
> pictures
> of 900mhz antennas, but there's not much info there.
>
>-TIA,
>Uttam
>

Can you make some fotos and post them somewhere?
What is the precise modem frequency, 869, or 900 or 915 Mhz?
Reverse WLAN adapters of different genders are available.
e.g. http://www1.at.conrad.com
enter SMA REVERSE into the search field.

A whip antenna requires radials at the footpoint to get 50 Ohm
impedance. Two radials are good enough, more radials
are just a little better, this is known as "groundplane antenna".
Just google, e.g.
http://netsh13.morpheus.net-build.de/wiki/index.php?title=Jochens_Groundplane
Make the dimensions of the whip and the radials  about a quarter
wavelenght in free air, shorten them by guesswork when mounted
on a plastic material.
http://radiation.weblife.at/


w.