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Hughes HX50 Installation Angola - Need Help

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dewholden
Ex Member


Nov 10th, 2011 at 1:20pm  
Hi all,

My name is Daniel Holden, and I'm attempting to point a VSAT dish with a Hughes HX50 modem, from Bentley Walker, but so far with no luck. I am an IT professional but have very little experience with VSAT antennas.

I have set up the dish and pointed it to the suggested values, in order to point at T11N at 37.5 degrees west.

My coordinates are:-14.92501666666 South, 13.4997111111 East.

Dish elevation: 29.87 degrees
aimuth: 289.34 degrees (magnetic north)
polarisation angle: -108.92 degrees

LNB model: 1501882-0002

I purchased a Maxpeak SAM-lite satellite meter, at Bentley-Walker's suggestion.

I am currently getting a 65dbuv reading on the meter, but that does not change at all when rotating the dish.

The signal strength indicator on the modem interface gives me a reading of 18.

I have read through all the posts that have similar problems as mine, and gone over all the reccommendations, but so far have not been able to get a lock on the satellite signal.

What might I be doing wrong?

I really appreciate any help with this because, as with most setups, there is a time limitation on it.

Please let me know if I have to supply any other information.

Thanks
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Eric Johnston
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Reply #1 - Nov 10th, 2011 at 2:19pm  
Polarisation
Your polarisation adjustment angle is, according to my calculation -71 deg, which means anticlockwise rotation of the feed assembly, as viewed looking forwards towards the satellite in the sky.
( Your figure of -108.92 is the same thing but with a different viewpoint and direction. )
The adjustment amount (-71 deg) needs to be applied after you have set an initial nominal position.

I've just called Bentley Walker.  In your case, for HX50 service on the T11 satellite, the name of the downlink polarisation towards you is called Horizontal.  It should tell you this in your documentation.

So set your polarisation to Horizontal initially.  In the case of the Hughes Universal LNB, part number 1501882-0002, the receive polarisation is the direction of the LNB F connector cable. So I suggest you rotate the feed assembly till the LNB cable sticks out at the right hand side (as viewed with you facing forwards towards the satellite in the sky).  Then apply the adjustment amount, rotate the feed anticlockwise by an amount of 71 deg. The cable connector of the LNB will come upwards.

Finding satellites
Your meter will make some indication if any satellite is seen.
If you find any satellite, then measure and mark the scales immediately so you can always get back to this first found satellite.  It is easy to then move along the orbit to the wanted satellite. For you in Angola the satellites are in a sloping line from low down in the west to high up in the north.
Your azimuth bearing angle is approx north west.
If your dish has a beam elevation scale on the back set it to 30 or 31 deg. If your dish has a grey wedge shaped box at the back the rear surface of the box is at right angles to the beam direction. Set to 30 or 60 deg using an inclinometer.
See: http://www.satsig.net/pointing/how-to-make-inclinometer.htm
This image shows how to use it
...
In this example the beam elevation is set to 48 deg.  You need 30 deg.
Normally, to find the wanted satellite you set the elevation accurately to maybe 31 deg, then swing the dish boldly sideways to find the satellite.
It takes at least 30 minutes to peak up. Maybe longer.  Accuracy is important and 1/6th of turn of the nuts matters.  As you tighten the various bolts you need to continue to make small adjustments. Do the elevation last.

Signal indications
Your meter will give an excellent indication on any and all satellites.  It may say "satellite found" if its programming matched your LNB, polarisation frequency band and satellite.
Your HX50 modem displays the signal in a scale from 0 to 100.  The scale range 0 to 29 is noise power and this is excellent for finding any and all satellites.  If the modem tuning and , carrier symbol rate matches what comes out of the LNB then the HX modem will jump into the signal quality range 30 - 100. Expect to peak up in the 90 range.

Programming the HX50 modem
You should have a configuration sheet with details, such as frequency and symbol rate etc., for you to input to the HX50 config page .
You may also have a cfg file whic needs to loaded into the HX50 to set the text in the LNB type pull down menu. Can you selct the correct LNB type on the HX50 config page ?

Warnings
Power off at the mains wall switch before any work on any cables. Never connect or disconnect the coax cables with the power on.
Leave the low voltage multiway power connector joined to modem at all times.
Waterproofing of the outdoor F connectors is essential.
Tighten the F connectors with firm finger force only, Do not use a spanner, which may permanelty damage the inside of the modem, LNB or BUC.

Best regards, Eric
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« Last Edit: Nov 10th, 2011 at 3:20pm by Admin1 »  
 
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dewholden
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Reply #2 - Nov 10th, 2011 at 3:16pm  
Hi Eric,

Thanks for the quick reply and for your time spent.

I have adjusted the dish elevation to 31 degrees, and also rotated the LNB to 71 degrees starting from the postion with the LNB cable pointing to the right, with me looking towards the satellite in the sky. However, when I sweep the sky left and right, 30 degrees at a time, I still get only 66-68 dbuv signal reading on the meter and the modem interface shows a signal reading switching back and forth between 15 and 20, continuously, even with the dish stationary.


HX50 Modem configuration
In the LNB list, I have Standard, Universal and three other part numbers, none of which are the one I have. I am assuming I should select Universal, from what I have read.
Thanks again.

Daniel
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Admin1
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Reply #3 - Nov 10th, 2011 at 4:05pm  
When you rotated the feed system by an amount of 71 deg, the LNB cable connector, which was initially to the right should now be pointing high up on the right hand side. All viewed with you facing forwards towards the satellite in the sky.

Power off at the mains wall switch before doing anything with the coax cables.

If you omit the meter, check that the LNB cable goes from the LNB to the modem receive input socket. (i.e. check your cables are not crossed over).  The centre wire of the F connector plug should be about 1mm proud of the rim. When screwed in, the centre wire should go smoothly into the hole and not 'push back' the cable.  The braid of the cable must make good contact with the plug outer shell. There must be no fragments of braid wire or foil sheath short circuiting the cable.

The modem display should be in range 0 to 29 initially and will go up when any satellite is found.  Putting you hand over the feed may make a very small increase.  Look out for any tiny increase indicating that you getting close to a satellite.

Try different elevation angles like 30, 32, 34 as the initially slack bolts allow the dish to sag down.

If you use the meter then follow instructions from Bentley Walker or from the meter manual.

Select Universal in the LNB pull down menu. Set all parameters as told in the config sheet (frequency, symbol rate, IP addresses, LNB type, etc).

Best regards, Eric.
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dewholden
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Reply #4 - Nov 10th, 2011 at 4:29pm  
Hi Eric,

With a bit more patience, and an hour and a half later, a managed to find signal. I guess I just wasn't being precise nor patient enough. Smiley

I am now getting a signal strength of 85. After achieving this, I experimented extremely small increments, both postivie and negative, of azimuth, elevation and polarization, but the best I could get was 85.

Is there any way that I can get a better reading, or is this usually good enough?

I am going to go ahead and contact Bentley Walker for activation.

Thank you very much for your great forum and you excellent help!

Daniel
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« Last Edit: Nov 12th, 2011 at 8:59am by Admin1 »  
 
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USN - Retired
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Reply #5 - Nov 10th, 2011 at 6:57pm  
Assuming you've got a 2 watt transmitter, that should give you perhaps 40 points of rain fade margin. If it was a receive only system, the modem can potentially maintain lock until the SQF drops close to 30. But given the small transmitter, it's usually the transmitter that drops lock first; typically around 40-42 SQF. If however you have a transmitter rated higher than 2 watts, the rain fade margin increases accordingly.

//greg//
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dewholden
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Reply #6 - Nov 11th, 2011 at 3:28pm  
Hi all,

After contacting Bentley Walker to activate, we found that apparently our antenna wasn't transmitting properly, as I am getting:

Transmitter adjusting for optimal network timing. (TxCode 9)

According to Bentley-Walker tech support (who have been extremely accomodating and helpful), in order to activate I should be getting Tx8.

After looking at photos of my setup, they suggested I change the polarization by 180 degrees, instead of the LNB pointing skywards at an angle of 71 degress anti-clockwise, facing the dish, it should be 71 degrees clockwise, facing the dish, so that it is pointing downwards. After having made this change, I am still getting Tx9.

Any suggestions?

We currently have excellent receive signal so I am confident that the dish is correclty pointed.

Thanks,

Daniel
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Eric Johnston
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Reply #7 - Nov 11th, 2011 at 4:35pm  
Transmit timing
Explanation (you should see something like this if you click on the Code 9 on your screen):
9  The satellite transmitter is adjusting for optimal network timing.
This condition typically occurs when your <type of modem> is first commissioned, is being ranged, or the first time it is used for data traffic. This must occur before the Indoor Transmit Unit is able to transmit successfully. Typically, this process usually takes less than a minute.


Transmit timing has to do with the range to the satellite. For ranging to start successfully the initial range is estimated from your lat/long location and satellite location. Until ranging is accurately completed your uplink test bursts may collide with normal uplink traffic bursts from other sites. Once one of your timing test bursts manages to get through to the hub (i.e. it did not collide) the hub will then adjust your transmit timing offset so that you transmit in a clear TDMA time slot in future. During the day, due to the slight satellite movement, the timing of everthing gets shifted left or right to keep everyone transmitting in clear time slots - as far as possible ! Read more about how does TDMA work.

I would check that the satellite longitude and site lat/long coordinates you have put in on the config screen are correct.
T11N Sat longitude is 37.5 West.  Don't put a minus sign in front of the 37.5  Satellite orbit locations are normally integer degrees. I don't know if that box accepts decimal degrees. What did BW say to type in that box?

Your site:
You say 14.92501666666 South, 13.4997111111 East
These look like decimal degrees
Check here http://www.satsig.net/maps/satellite-tv-dish-pointing-south-africa.htm if necessary.
then input...

Latitude 14 deg 55 min South
Longitude 13 deg 30 min East

Check that your Transmit cable is properly connected at both ends (note IFL socket on the BUC). Power off at the mains wall switch before inspecting cable connectors.

Polarisation
I doubt that transmit timing has anything to do with polarisation angle.

For your site and T11 satellite, all the possible polarisation angles are:

Horizontal name receive polarisation:
Start with the Universal 1501882-0002 LNB cable connector sideways (either side is good)
Adjust 71 deg anticlockwise, while facing forwards towards the satellite in the sky. If the LNB hits the metal start on the other side.

Vertical name receive polarisation:
Start with the Universal 1501882-0002 LNB cable connector directly upwards or downwards (either is good).
Adjust 71 deg anticlockwise, while facing forwards towards the satellite in the sky. If the LNB hits metal, start 180 deg the other way.

If you set the polarisation exactly wrong (i.e. 90 deg wrong choice) then you should get none of the wanted receive signal at all.
wxw
Best regards, Eric.
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« Last Edit: Nov 12th, 2011 at 10:37am by Admin1 »  
 
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