[amsat-bb] Re: Gain VS Bandwidth at 2.4GHZ

Matthias Bopp matthias.bopp at gmx.de
Sun May 17 07:37:55 PDT 2009

Hi Luc,

a linearly polarized antenna on a satellite means, that you will see
different polarization at different times and different locations on
Earth. Assume the satellites transmit vertical polarization but "tumbles"
then the polarization you are receiving is always linear but can vary
between vertical, diagonal, horizontal ...
Therefore it is better if the satellite and the station on earth both use
circular polarization. If this is not possible due to constraints on the
satellite I think it is still better to have a circular polarized antenna
at my station as the losses due to varying linear polarization will always
be only 3dB and thus no strong fading due to polarization will accur.
Please note that a tumbling satellite will most likely still generate strong
fading as the antenna on the satellite will never have a perfect
omni-directional behaviour.

Best regards

Matthias   DD1US


-----Ursprüngliche Nachricht-----
Von: amsat-bb-bounces at amsat.org [mailto:amsat-bb-bounces at amsat.org] Im
Auftrag von Luc Leblanc
Gesendet: Sonntag, 17. Mai 2009 14:09
An: amsat-bb at amsat.org
Betreff: [amsat-bb] Re: Gain VS Bandwidth at 2.4GHZ

On 16 May 2009 at 17:27, Roger Kolakowski wrote:

A part of my mystery is solved WiFi and WiMAX I am not a big fan of WiFi as
i have some security concern but i discover that i don't have 
the best antenna for 2.4 and fiddling with it is not an option. A true 2.4
is in the mail to replace it and with 2 antennas now i will be 
able to install them to have vertical and horizontal polarisation and i will
see if there is some improvement at 2.4ghz when switching 
between them. Nobody answer me back regarding the S band linear "not
circular" AO-51 antenna but the fades are probably due to some  
antenna blocking than anything else. On the last S band session me and Clare
VE3NPC noted that the fades does not happen at the same time 
on our respective QTH there is surely not some selective circular
polarisation path?

> This was probably just a typo; if so, pardon the reply...
I was mixing both...hi 
> Wi-Fi and Wi-Max are different things.  An antenna designed for Wi-Max
> may not operate very well, as you describe, on 2.4 ghz.  Wi-Fi's
> 802.11b/g is on 2.4 ghz (channel 1 is right on top of our allocation),
> so a properly designed Wi-Fi antenna could be good for 13cm Ham
> applications.
> >
> Enjoy the new toy,
> Greg  KO6TH

Some experimenting to come on the next S band session.

Luc Leblanc VE2DWE
Skype VE2DWE


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