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Pages: 1

HX50 Installation in Nigeria - Assistance Needed

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Jul 11th, 2008 at 5:42pm  
Hello,

We have a HX50 setup pointing to W3A in Nigeria. The signal strength is 55, the installer could not get the signal higher than that. What can be done to increase this signal?

We are using a 1.2m Prodelin antenna. We easily got elevation, azimuth, latitude & longitude etc from this site (satsig.net).

Latitude = 7.7600, Longitude = 4.4385
Lat    = 7 degrees,   45.6 minutes   North
Long = 4 degrees,   26.3 minutes   East

Dish elevation= 80.4, Azimuth= 165.7 (magnetic compass), Polarisation= -18.2

We have adjusted the BUC polarization, but still we are not able to get anything more than 59. Any help will be appreciated.

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Reply #1 - Jul 12th, 2008 at 9:49am  
Dear sir ,


i suggest you get 1.8m dish for your site, w3a signal is not always good at 1.2mdish , if it fails pls contact your service provider for correct eirp parameters, ,also check your symbol rate
thanks

pius ukachukwu
skytel communications ltd
08032706565
skytelcom2000@yahoo.com
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Reply #2 - Jul 24th, 2008 at 2:48pm  
Where is the location of the site,maybe a personal visit can help you out,cos i know of sites on 1.2m dish size and on w3A dat does good signal.
tunde300us@gmail.com
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Eric Johnston
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Reply #3 - Jul 24th, 2008 at 3:52pm  
Please send images of your feed assembly, the side view of the dish and also of the back of the dish to eric@satsig.net and I will insert them here.

Best regards, Eric.
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Reply #4 - Jul 25th, 2008 at 9:49am  
Using Hughes HX codes rates, 1.2m is more than sufficient for W3a. Please contact james@bentleywalker.com if your pointing issues remain unresolved and we will be pleased to assist further.

James - Bentley Walker Ltd
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Reply #5 - Jul 25th, 2008 at 10:29am  
We normally are seeing around 73 to 74 in Lagos on a 1.2 dish clearly there is something not quite right with the install of the dish as you are around 25% less than normal , could you send us some digital photos of the installation ........to Anthony@BentleyWalker.com
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Eric Johnston
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Reply #6 - Jul 31st, 2008 at 6:23pm  
Thanks for the pictures. I presume they came from Priest and refer to the original message of this thread.

...  ...

...  ...

You have set the LNB at the top which means you now have exact horizontal polarisation.  You need to apply -18 deg polarisation adjustment.  While facing towards the satellite the feed and BUC need to be rotated 18 deg anticlockwise.  There is a good scale on the white yoke to measure the amount of degrees.

I don't recognise the feed arm. If it is not the one that came with the dish please measure the diameter sideways across the dish so we know the dish size.  Also measure the distance from the lower rim of the dish to the lower rim of the feed window and from the top of the dish to the lower rim of the feed window.  

Best regards, Eric.
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Reply #7 - Jul 31st, 2008 at 7:36pm  
Dear Eric,

Thanks. We have adjusted the polarization. The dish is 1.2m prodelin make. I have sent another picture of the back.

...

Best regards
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« Last Edit: Jul 31st, 2008 at 9:03pm by Eric Johnston »  
 
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Reply #8 - Aug 1st, 2008 at 11:24am  
I don't recognise the dish.   If someone else has a good dish just like this, please say here what are your feed position measurements.

If the feed arms did not come with the dish and there is doubt about the feed position then:

Measure the diameter sideways across the dish so we know the dish size.

Multiply by 0.6 (just a guess as to the likely f/D ratio) to get the focal length. Most older dishes have an f/D=0.6 but there are variations.  Some modern dishes have f/D=0.8 to improve the cross-pol performance, and need longer feed arms and a larger diameter feed window aperture.

Set the focal distance from the lower edge of the dish to the throat of the feed horn (where the conical part becomes a circular waveguide).

An exact side-on view of the dish would help so that the position of the feed relative to the top and lower edges of the dish can be measured.

This image below shows a modern Prodelin 1.2m dish:
...
This shows where to take measurements.
Note that the phase centre of the feed horn is not at the window aperture but further down inside the horn, towards where it changes to a circular waveguide, so the focal length is longer than the lower white line.  The position of the phase centre varies with feed type and frequency, sometimes it is at the aperture, sometimes further inside, depending on the flare angle.

Best regards, Eric.
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Reply #9 - Aug 18th, 2008 at 1:36am  
Its such a funny site,i have seen the pictures and i have also spoken with the site owner.I had some reservations with the location of the dish and thought firstly a Re-location might be needed and a personal visit
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Reply #10 - Aug 24th, 2008 at 6:24pm  
Hi List

Did this site Work and what was the solution to the problem
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Reply #11 - Aug 28th, 2008 at 7:21pm  
Hi,

the site is still not working.
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Eric Johnston
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Reply #12 - Aug 28th, 2008 at 8:22pm  
If the site could measure the vertical and horizontal diameters of the dish we could determine if it is an offset dish with a slightly elliptical outline, or an axisymmetric circular dish.

As shown, if has an offset type feed arm attached, with distances from the botton rim of the feed horn to the bottom edge and upper edge of the dish not yet known.

I do not recognise the dish.

Best regards, Eric.
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Reply #13 - Aug 30th, 2008 at 4:36pm  
did you received the LNB fixed with feed horn or you assembled it on site ?
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Reply #14 - Sep 1st, 2008 at 10:32pm  
Hi helloworld,

The LNB was assembled on site.

Regards
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Eric Johnston
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Reply #15 - Sep 2nd, 2008 at 8:31am  
... ...
As shown you have set the LNB at the top which means you now have true horizontal polarisation starting position.  You need to apply about -15 deg polarisation adjustment.  While facing towards the satellite the feed and BUC need to be rotated 15 deg anticlockwise.  There is a good scale on the white yoke to measure the amount of degrees.

If the site could measure the vertical and horizontal diameters of the dish we could determine if it is an offset dish with a slightly elliptical outline, or an axisymmetric circular dish.

If you can put a straight piece of wood up the front of the dish and measure the depth at 10cm intervals all the way from bottom to top I can work out where is the focal point.

As shown, if has an offset type feed arm attached, with distances from the botton rim of the feed horn to the bottom edge and upper edge of the dish not yet known.

Best regards, Eric.
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Reply #16 - Sep 2nd, 2008 at 4:37pm  
Eric

Looking at the picture very closely it seems LNB is not assembled properly. look at the last post picture above, the Model/Sr No striker is suppose to be up or down but it is on side.

If wrong correct me.

Regards
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Eric Johnston
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Reply #17 - Sep 2nd, 2008 at 8:44pm  
Yes, the LNB may, in error, have been attached at its square flange with the rectangular waveguides crossed relative to each other.  The site needs to check this and make sure that the two rectangular waveguides match up.

The images below show an LNB, oriented for horizontal polarisation, and with the F connector socket offset from the centre line, so it is along the broad side of the waveguide.   Remember that horizontal polariation is with the broad faces of the waveguide on either side.
... ...


The antenna is a real puzzle.  I'm not sure if it is an offset design or not, and if it has the correct length feed support arms.

Best regards, Eric.
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« Last Edit: Sep 3rd, 2008 at 2:38pm by Eric Johnston »  
 
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Reply #18 - Sep 3rd, 2008 at 1:44pm  
Dear Eric,

Thanks for your insightful inputs. I really dont know much about installing this stuff.But what I will do is to go to the remote site this weekend and get you the measurements (if I can), and close up pictures of everything.

Thanks
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