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Universal LNB compatibility with different Horn

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Apr 30th, 2011 at 10:20am  
I recently received an HX Universal LNB (1501882-0002) from BW without the feed horn since I already had a Hughes standard BUC/LNB I use with my 1.2 m dish.

My question is:
Would the new universal LNB be conpactible with the old standard feed horn I already have?

Given the emphasis on the position (relative to the feed arm) of the 505 mark on the feed horn that usually come with the univeral LNB, I am wondering if the Universal LNB would be compartible with any other feed horn type?

My dish is not exactly like the "Prodelin" extensively talked about in this forum because it does not have the 1 fat feed arm and 2 support, but instead has 3 support arms with the horn/LNB assembly held at the centre where the 3 support ams converge.
So I think adjusting for polarization will be slightly different as described in the forum.

I will really appreciate some advice from the experts.
Thanks.
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« Last Edit: May 1st, 2011 at 9:23am by Admin1 »  
 
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Eric Johnston
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Reply #1 - Apr 30th, 2011 at 1:14pm  
The mode matched feed horn (with the 505) is designed to form part of an offset feed designa antenna system. The feed horn and its adaptor tube should be regarded as a fixed part of the antenna, always oriented so the 505 is away from the feed support arm. The asymmetric feed horn cancels out the cross-pol of the offset dish geometry and the result is near perfect cross-pol performance.

The Hughes Universal LNB/OMT (P/N 1501882-0002) may be used with any antenna.  It is unusual in that the LNB and OMT are integrated together. There is one rectangular waveguide port, for the transmit direction from the BUC.

If you have a 505 type feed horn you may attach an Universal LNB/OMT at any of the 30 deg positions.  Receive polarisation is the direction of the Universal LNB/OMT F connector.

Best regards, Eric.
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« Last Edit: May 1st, 2011 at 9:23am by Admin1 »  
 
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Reply #2 - Apr 30th, 2011 at 7:19pm  
Eric,
Thanks for the information and clarification.
From your feedback, I understand that I may use any feed horn (that comes with a particular dish) with the Universal LNB.  Yes.
And if I am using the mode match feed horn, it must be used with its adaptor tube together to form the feed horn assembly and the 505 always oriented away from feed support arm.

In my case, I do not have a mode match feed horn, but a standard circular feed horn which I have now attached to the universal LNB.

I have commenced the process of pointing to the satellite, but has no luck finding the satelite (Telstar 11N) after two days of trying. Very fustrating indeed!!!
I have used the resources on this website to calculate the elevation and azimuth, along with the satelite meter I bougth from BW (Maxpeak), but still can't find the Telstar 11N 37.5W from my location in Benin City, Nigeria (lat=6.33 long=5.63).
I have also setup the HX50 modem on my pc as an additional source for monitoring signal strength, but be best I have read in terms of signal strength was 22 at some elevation 10 deg higher than the calcuated 40 deg. I need a signal strenght greater than 30 to confirm satelite location.
I am a bit confused now, I thought locating the satelite was straight forward.

Is getting the polarisation right very critical for locating the satalite?
At the moment, I am concern with locating the satelite first, not signal peak up. My suspision at this time is "wrong polarization". But is getting an accurate polarization a crucial requirement for locating the satelite in the first place?

I will really appreciate your help.
Thanks.

Text clarified by Eric !
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« Last Edit: Apr 30th, 2011 at 8:23pm by Admin1 »  
 
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Eric Johnston
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Reply #3 - Apr 30th, 2011 at 7:53pm  
From your location the satellites appear in a steeply sloping line going up the sky in the west.
http://www.satsig.net/maps/satellite-dish-pointing-lagos-nigeria.htm
Elevation=40, Azimuth 267 Pol=+81 deg

Once you have found any satellite note that the adjacent ones will be higher up and slightly left or downwards and slightly right.  Note and mark the position of a found satellite and progress from there to the next satellite.

The Hughes signal measurement system works in two ranges. 0-29 and 30-100

Each time you pass a satellite you will get readings in the range 0-29.  29 is a very powerful satellite signal. Find satellites and get familar with moving from one to the next.

If you have an elevation scale on the bracket behind the dish try to find a satellite that results in a reading of 40 deg elevation.  If you can do this then you have likely found the correct satellite, even if the reading won't go higher then 29.

If you have no elevation scale, find out the offset angle of the dish from the dish installation manual. (e.g. 23 deg).  Set the front face of the dish vertical and the beam elevation is then 23 deg.  You want a beam elevation = 40 deg, so tilt the top of the dish backwards by an amount of 17 deg.  An inclinometer held against a plank of wood up across the front will help you measure this amount of movement.  http://www.satsig.net/pointing/how-to-make-inclinometer.htm

If the Hughes screen measurement won't go above 29 it is due to some problem: wrong polarisation, wrong 22kHz tone, wrong tuning, wrong symbol rate, wrong SBC.cfg file, wrong LNB type in the pull down menu. When all these things are right the receive LED will light up and you should peak up, typically to 91 or thereabouts.

Your meter works similarly to the Hughes modem.  The meter gives some basic power reading on any and all satellites but will only display "SATELLITE FOUND" if the polarisation is correct, if the meter tuning is correct and if the LNB 22kHz tone control is correct. The meter is typically programmed to look for a suitable TV carrier on the wanted satellite, in the same polarisation and same part of Ku band as your wanted satellite internet carrier.

Your polarisation adjustment is 81 deg clockwise, as viewed facing forwards towards the satellite in the sky. I would peak up on each promising satellite and then turn the feed 90 deg so as to test both polarisations.

On the Universal LNB, the LNB connector is the direction of receive polarisation.  The connector should stick out in one of these directions:
...

Note this view is with you facing towards the satellite in the sky with +81 deg clockwise adjustment applied.  The red line is along the orbit equator and is called Horizontal polarisation name.  Only one direction of polarisation (red or black) will work.

The other satellites are up and down the red line !

If you were on the equator the adjustment would be 90 deg and horizontal name polarisation becomes vertical relative to your ground when facing directly west.
wxw
Best regards, Eric.
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« Last Edit: May 1st, 2011 at 11:34am by Admin1 »  
 
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Reply #4 - May 1st, 2011 at 10:35am  
Good Morning Sir,
To add further to the advice provided by Eric; you will also need to ensure that you have subtracted the offset from the elevation of the dish (18.5 Degrees). Based on the provided GPS in your previous update I have calculated the below alignment angles:

Dish elevation (deg): 39.78°
Dish elevation with offset removed (deg): 21.28°
Dish azimuth (deg east relative to true north): 263.3°
Dish azimuth (deg east relative to magnetic north): 265.74°
Polarization angle (deg): 80.79° (Counter clockwise rotation whilst standing in front of the feed assembly, facing the dish)

With the MaxPeak meter you will receive a “SAT FOUND” message when you locate the correct satellite, until then you will see “SEARCHING”.

To ensure that nothing is overlooked, please provide photographs of the dish installation, feed assembly and line of sight. If you could also provide a screenshot of the “VSAT Manual Commissioning Page” so that we can help to verify your modems configuration. Please send the requested information to the below email address:

gary@bentleywalker.com

Best Regards, Gary
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Reply #5 - May 3rd, 2011 at 4:51pm  
Eric,
You have been extremely helpful and usefull to me!
Simply put: YOU ARE FANTANSTIC!

I followed the direction provided by you and others in this forum and final got my VSAT up and running. I now have access to the internet!!!

I must say that this website is very rich in terms of resources to help with all aspects of VSAT technology. I consider www.satsig.net the "final bustop" to all VSAT related enquiries.

Please continue the great work and keep the flag flying.

Once again, thanks Eric and co.!
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