[linux-dvb] Circular polarization

DUBOST Brice dubost at crans.ens-cachan.fr
Fri Mar 31 22:27:46 CEST 2006


Robert Schlabbach wrote:
> From: "DUBOST Brice" <dubost at crans.ens-cachan.fr>
>> In regular cards there is (in general) two orthogonal linear polarizers.
>> So you can try with any linear polarization but you'll get -3dB on your
>> signal
> 
> AFAIK there are *no* polarizers on the card. The polarizer is contained in
> the LNB. So you only need an LNB with circular polarization. If that LNB is
> controlled with the same signals as common LNBs with linear polarization
> are (where +13V sets vertical polarization and +18V sets horizontal
> polarization), you can use the same drivers without changes, and only have
> to know what circular polarizations horizontal and vertical correspond to.
> 

Hello
You're right, I wrote card but I was meaning LNB

And if you use a wrong polarisation basis (wrong LNB) (it's not as in
the same basis (linear or ciruclar) but the wrong polarization
(horizontal,vertical for linear and right, left for horizontal) ) wou'll
divide the signal by two.

Regards,

-- 
Brice




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