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Linear Pol with Circular pol

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Gomes
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Bangladesh
Mar 25th, 2007 at 9:06am  
Extended C- Band at HUB site with Linear Pol and C- Band with Circular Pol at remote site - does work together?
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Eric Johnston
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Reply #1 - Mar 25th, 2007 at 10:50am  
If the hub site is in the same beam coverage area as the remote sites then all earth stations (hub and remotes) must use the same type of polarisation (linear or circular).

If your hub is in a different satellite beam, then you need to clarify what is the satellite polarisation in the hub beam and what is the satellite polarisation in the remotes beam.

If you have a remote site with circular polarisation and need to change it to linear, this is easy.  Simply remove the polariser ( or rotate the OMT relative to the polariser so that the polarisation planes line up with the pins/slots in the polariser.  The polariser is then non-functional - it just attenuates the tx and rx signals very slightly.  Normally, for circular polarisation, the OMT is at + or - 45 deg to the pins, for left hand and right hand CP)

Remember that once you are operating linear polarisation you will need to accurately adjust and align the polarisation angle.  Call the hub and they will help talk you into the deep narrow null while you transmit an CW test carrier.  Polarisation rotation adjustment to 1 deg accuracy is required.

Best regards, Eric.
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