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HX50 dish alignment with mode-match feed

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Eric Johnston
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Posts: 2109
Apr 19th, 2011 at 4:15pm  
Applies to: Hughes Universal LNB, Hughes HX system and Prodelin 1.2m dish with mode matched feed, and large polarisation scale behind the dish.

Bentley Walker have put up a draft video regarding the set up of 1.2m Ku band dish as used with their HX service.
See: YouTube page: https://www.youtube.com/bentleywalker1

The method described for polarisation setting, by rotating the radio assembly in its yokes, is reported to achieve acceptable cross-polarisation performance. This is the same adjustment process as used in older VSATs and all satellite TV dishes. It is simple and easy to implement.

My preference, being a perfectionist (!), is as follows:

While the feed arm is at the bottom, install the Universal LNB/OMT/BUC in its yokes so that the Universal LNB F connector points sideways. Assemble the feed horn and its spacer tube to the LNB/OMT so that the 505 on the feed throat is directly away from the feed support arm. Having the Universal LNB F connector pointing sideways gives a Horizontal receive polarisation starting position.  If Horizontal receive is what you want then, while behind the dish and using the big scale, simply apply a +ve polarisation adjustment amount clockwise, alternatively a –ve polarisation adjustment amount anti-clockwise.

If Vertical receive polarisation is required, follow the above assembly, then, while behind the dish, and using the big scale apply an initial 90 deg polarisation adjustment so that the feed arm is at one side. The Universal LNB F connector will be now be aligned up/down. You are now at a Vertical receive polarisation starting position. Then, while behind the dish, and using the big scale, apply a +ve polarisation adjustment amount clockwise, alternatively a –ve polarisation adjustment amount anti-clockwise.

During commissioning Bentley Walker may ask for you to tweek the polarisation. A +/- 5 deg polarisation adjustment may be applied at the feed/radio unit yokes.


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https://www.satsig.net/pointing/how-to-make-inclinometer.htm
wxw
Best regards, Eric.


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