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Re: Up and dwnlink polarization of HAMSAT



Hi Don,

>I may have read incorrectly, but I thought polarisation was determined by 
>the rotation of the electric field about the axis as the wave moved AWAY 
>from the source.  If this is true, wouldn't the polarisation be opposite as 
>it arrived on Earth?  i.e. transmitting with an LHCP antenna in space would 
>be best received with an RHCP antenna on Earth?

I am sorry but your statement is not correct.
RHCP send from space can best be received with RHCP on earth.

I try to explain:
The rotation of the electrical field must be seen from the backside of the 
antenne, towards the other station. Then with RHCP the field rotates 
clock-wize.
With a helical antenna you will see the turnings as how the field rotates 
from the back to the frond (towards the other station).

The satellite will see the waves going towards earth in clock-wize way...
Now imagine the waves are comming towards you (on earth), then they will be 
like going like anti-clockwize. This seems opposite of your helical winding, 
BUT the waves are going the other way.

The waves come from the front to the back in anti-clock wize way and follow 
the windings of the helical antenna.

Its a symple way to imagine circular polarization...

>
>73,
>Don

73
William
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