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DirecWay Dish Problems in Iraq

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Apr 10th, 2007 at 11:37am  
Hello All,

I recently was given a Hughes/Direcway VSAT system,  which the original owner said it worked for him here in Iraq. Once everything was set back up, I went with a new provider, programmed the DW6000 modem per provider instructions. Everything was looking good to go until aiming the dish. The signal strength will not go past 10-12 no matter where the dish is aimed.

A few VSAT techs came to the scene, replaced the coax cables, hooked up a sat finder tool, spectrum analyzer etc.... reaimed, adjusted the polarization but got nothing from the dish. Each one told me the dish is picking up a little noise and that's it.

So now what do I do? I've provided a few links of what my dish looks like. I'm told the LNB could be bad or the whole nose piece?

What should I replace first?
Can someone out there supply me with the parts I need with prices?

http://www.darkgarrison.org/dish1.jpg

http://www.darkgarrison.org/dish2.jpg

http://www.darkgarrison.org/dish3.jpg

http://www.darkgarrison.org/dish4.jpg

http://www.darkgarrison.org/dish5.jpg

http://www.darkgarrison.org/dish6.jpg

I hope these pics help identify the type of dish parts I need.

philipg






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Reply #1 - Apr 10th, 2007 at 1:01pm  
The device from which your modem gets the received signal is the LNB. It's that small rectangular component that the cable's attached to in dish4.jpg. They're cheap, readily available, and inexpensive to mail.

But from what I see in the other photos, you could have several other problems that could be impeding your progress. Not the least of which is in dish5.jpg. The Mylar feedhorn window is missing. Your problem could be no more complicated than a family of sand critters living in your waveguide. And I also noticed in dish4.jpg that the feedarm looks homemade. If the fabrication is off by even one degree from original, it's going to change your offset - which directly affects the accuracy of your pointing angles. And it looks like the whole rig is sitting on top of a ConEx box. All that metal around there does strange things to RF signals. 

And finally, none of the photos suggest that AZ/EL/Pol have been set for pointing angles typical of usage in Iraq, and that the pedestal is only held in place with two small sandbags. Are you just waving the thing around by hand to try and find a satellite signal?

//greg//
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Reply #2 - Apr 10th, 2007 at 1:11pm  
well, the most crucial thing I can see here is that the basement of the dish is not really good, as mentioned by Greg.
I also think it is a good thing to make sure you have a good line of sight to the satellite.

LNB can get broken, sure. When the installers connected to satfinder to it, could they identify that the level of noise got higher or it just stayed the same?

Good Luck,
Nimrod
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Reply #3 - Apr 10th, 2007 at 3:43pm  
Thanks for the reply,

I'll try to answer the problems you noticed best I can starting with the dish5 pic. The window you refer to being missing is indeed there. It was checked by the Vsat techs who cleaned it off. It looks like a plastic window.

Not to sure what the wave guide is? I could check this though, don't know if the vsat techs verified this.

As for the feed arm, I've found atleast 4 other direcway vsat dishes in my area which have the same type feed arm.

The conex you see in the picture is 90% of the living quarters for US folks in iraq. Most of the Vsats are setup in the same fashion as mine.

I did receive angle degree instructions from the provider, which has the dish aiming low on it's axis. Reason why you see only a few sandbags on the base. The Vsat techs tried to aim the dish by hand since thier equipment wasn't picking up anything on the LNB.

Hope this clarify things a bit. Once again thanks for the helpful reply.

PhilipG





USN - Retired wrote on Apr 10th, 2007 at 1:01pm:
The device from which your modem gets the received signal is the LNB. It's that small rectangular component that the cable's attached to in dish4.jpg. They're cheap, readily available, and inexpensive to mail.

But from what I see in the other photos, you could have several other problems that could be impeding your progress. Not the least of which is in dish5.jpg. The Mylar feedhorn window is missing. Your problem could be no more complicated than a family of sand critters living in your waveguide. And I also noticed in dish4.jpg that the feedarm looks homemade. If the fabrication is off by even one degree from original, it's going to change your offset - which directly affects the accuracy of your pointing angles. And it looks like the whole rig is sitting on top of a ConEx box. All that metal around there does strange things to RF signals. 

And finally, none of the photos suggest that AZ/EL/Pol have been set for pointing angles typical of usage in Iraq, and that the pedestal is only held in place with two small sandbags. Are you just waving the thing around by hand to try and find a satellite signal?

//greg//

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Reply #4 - Apr 10th, 2007 at 3:50pm  
Hello,

Thanks for the reply. The base for the dish you see appears to be very common atleast in the area I am in. I've compared my setup with many other Vsats in the area. I usually have more sandbags on the base however, during the dish aiming by the Vsat techs, they had to remove a few. The NSS6 satellite is very low on the horizon as the techs pointed out at 110 degree azimuth.

With the sat finder gear attached, it appeared the signal never changed no matter where they pointed the dish.

Hope this clarified a few things.

PhilipG


Quote:
well, the most crucial thing I can see here is that the basement of the dish is not really good, as mentioned by Greg.
I also think it is a good thing to make sure you have a good line of sight to the satellite.

LNB can get broken, sure. When the installers connected to satfinder to it, could they identify that the level of noise got higher or it just stayed the same?

Good Luck,
Nimrod

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Reply #5 - Apr 10th, 2007 at 5:02pm  
If you are in Iraq and want NSS6 at 95 east orbit longitude the pointing angles are here:
https://www.satsig.net/maps/satellite-dish-pointing-iraq.htm
e.g. approx 25 deg elevation, 110 deg azimuth and - 51 deg polarisation.

Without a clear sideways-on image of the dish it is difficult to assess what is the elevation angle you have set now; it could be about 20 to 35 deg.  See the slope of the red line from bottom of dish edge over top of feed horn in image below.  My guess would be that the front face of the dish needs to be almost vertical or even tilted forwards a bit.
...

Regarding feed polarisation angle
...
The polarisation angle shown here is:
If you are trying to receive vertical polarisation then the angle is -20 deg. (i.e. you have set it initially to exactly vertical and then adjusted it 20 deg anticlockwise while facing towards the satellite.  Negative means adjust anticlockwise)
If you are trying to receive horizontal polarisation then the polarisation angle is +70 deg.   Either way it is wrong by a large amount.
wxw
Another picture shows the polarisation angle like this:
...
It is now set so that
If you are trying to receive vertical polarisation then the angle is about + 20 deg.
If you are trying to receive horizontal polarisation then the polarisation angle is -70 deg.   Either way it is wrong by a large amount.

Best regards, Eric.

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« Last Edit: Apr 11th, 2007 at 11:32pm by Eric Johnston »  
 
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Reply #6 - Apr 11th, 2007 at 6:04am  
Hello,

Thanks for the great info. The dish in the pic isn't currently setup to aim at the nss6 satelite. I observed the vsat techs adjust the azimuth, polarisation etc. from the info obtained from the the satsig website dish pointing area, looking for the NSS6. When they failed to get a signal strength over 10-12, they begain to swing the dish by hand thus moving for a signal in any direction. They left the dish in it's current setting to extract numbers off the parts to go do some research they told me.


Just doing some research on my own to see the possibility of bad parts. I can put the dish back in it's regular position how they had it originaly, take few more pics and can post here.

philipg



Eric Johnston wrote on Apr 10th, 2007 at 5:02pm:
If you are in Iraq and want NSS6 at 95 east orbit longitude the pointing angles are here:
https://www.satsig.net/maps/satellite-dish-pointing-iraq.htm
e.g. approx 25 deg elevation, 110 deg azimuth and - 51 deg polarisation.

Without a clear sideways-on image of the dish it is difficult to assess what is the elevation angle you have set now; it could be about 20 to 35 deg.  See the slope of the red line from bottom of dish edge over top of feed horn in image below.  My guess would be that the front face of the dish needs to be almost vertical or even tilted forwards a bit.
https://www.satsig.net/images/30-deg-elevation-dish.jpg

Regarding feed polarisation angle
https://www.satsig.net/images/vertical-polarisation-minus-20-degrees.jpg
The polarisation angle shown here is:
If you are trying to receive vertical polarisation then the angle is -20 deg. (i.e. you have set it initially to exactly vertical and then adjusted it 20 deg anticlockwise while facing towards the satellite.  Negative means adjust anticlockwise)
If you are trying to receive horizontal polarisation then the polarisation angle is +70 deg.   Either way it is wrong by a large amount.
wxw
Another picture shows the polarisation angle like this:
https://www.satsig.net/images/vertical-polarisation-plus-20-degrees.jpg
It is now set so that
If you are trying to receive vertical polarisation then the angle is + 20 deg.
If you are trying to receive horizontal polarisation then the polarisation angle is -70 deg.   Either way it is wrong by a large amount.

Best regards, Eric.


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« Last Edit: Apr 11th, 2007 at 11:34pm by Admin1 »  
 
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Reply #7 - Apr 11th, 2007 at 7:23am  
Hi Philip,

I am afraid that at your specific situation, it is not really possible to help remotely, and you need someone professional at site. As mentioned before, the installation doesn't look so good.
If your techs can't troubleshoot it, let me know and maybe I will be able to connect you with someone professional in Bahgdad.

Nimrod
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« Last Edit: Apr 11th, 2007 at 11:36pm by Admin1 »  

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Reply #8 - Apr 28th, 2007 at 4:59am  
Phil - if your still monitoring this thread, drop me a private message.  I've got a team of contractors in SWA right now running around theatre tuning up systems on a gov't contract, but we always try to help out the troops when we can.  If they're anywhere near your FOB, I'll tell them to stop in and fix you up - they've got a full load of parts w/ them.

Ex
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Reply #9 - May 5th, 2007 at 1:19pm  
My company has bought 3 Direcway DW4020's to install at 3 different sites. Fallujah, Al Asad and TQ.  For some reason they(the company) bought the systems without installation.  I have some experience installing DW7000's in Mexico(shhhh),but none of that experience is of much help here.  I have discovered I have to "talk" to the remote(DW4020) via Telnet.  I had never even said the word, Telnet, until a week ago and now I am using it. Little by little I'm learning how to install these systems.  My reason for writing is-I know there are experienced installers, in Iraq and on TQ, that would love to help us out. So come on by the MAS site and see Bill at OSHKOSH TRUCK or call DSN 3424-470. Por Favor!
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Reply #10 - May 13th, 2007 at 11:23am  
Dear All

Feel free to visit our website
http://www.wafa.ae

to Help and Support and DW6000s, 4020s, and/or DW7000

regards
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Reply #11 - Oct 11th, 2007 at 11:05am  
Hi Philip

I saw your comment regarding a VSAT problem. Have you managed to come right with this? If not, I would like to make a few comments.
To check if the LNB is working, with the Transmitter disconnected and the sat finder connected to the receiver (LNB), if you move your hand in front of the horn, it should drop the level on the meter. If there is no change, purchase a new LNB.

There is one major problem that I saw on your pictures on the web (Pic#3). I see that the one arm is bent. This will completely change the focal point of the antenna and you will not be able to pan the dish no matter how new your equipment is. Straighten the arm.

Another possibility is that your LNB is in the wrong frequency range for your application.

In closing, I have experienced a lot of noise interference due to signal scatter caused by a corrugated metal roof.

Have a great day.

Chris
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Reply #12 - Oct 11th, 2007 at 11:51am  
[quote author=schroec link=1176201460/0#11 date=1192097155]To check if the LNB is working, with the Transmitter disconnected and the sat finder connected to the receiver (LNB), if you move your hand in front of the horn, it should drop the level on the meter. If there is no change, purchase a new LNB.[/quote]

Putting your hand over the feed horn will cause the sat finder level to drop ONLY if the antenna is already pointed at a satellite and already receiving a downlink signal.  The satellite signal is blocked and so less power is received.

If the antenna is not pointed at a satellite and is pointed at the cold sky away from any satellite then putting your hand over the feed horn will cause the sat finder level to increase.  When aimed at the blank sky, the LNB is then listening to the very cold, low level 'big bang', background deep space noise which is negligible.  The sat finder measures the noise from the LNB itself, which is proportional to its noise temperature. (say 65 deg Kelvin).   If you put your warm hand over the horn the thermal noise of your hand (temperature = 290 deg Kelvin) adds to the LNB noise temperature and the sat finder gives a larger reading.  The same applies if you point the antenna down at the trees, the ground or into a torrential rain storm of water droplets at 280 deg Kelvin.  The sun, at 10000 degrees Kelvin, will give a big reading.

Best regards, Eric.
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Reply #13 - Oct 11th, 2007 at 11:59am  
Six month old topic. Presumably abandoned, since there's no apparent follow-up by the OP as to whether he actually ever got it to work.

//greg//
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