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takoateli

join:2010-10-09

1 edit

[HN7000S] POL/Isolation problem

I've searched the forum and found some good information about my problem regarding other people's systems which were having problems regarding pol/isolation. It sounds like there's some extremely knowledgeable people here. Can anyone help me with this?

I'm located in Venezuela using service from a company called Bantel. I believe the underlying provider is actually Hughesnet. We're using an HN7000 modem. We are on the Hispasat Amazonas II satellite.

This service doesn't allow the end user to run the pol/isolation test from the terminal instead I have to contact Bantel and they have the test run. During that time the modem has a red status light and the transmitter code is 2 and it says the transmitter is in a test mode. Bantel tells me the results show numbers such as 30 and 6. The 30 number should be high and the 6 number should be adjusted to be as low as possible, and should be below 4. We have spent days trying to get the pol/isolation better and it can't be done.

The system is running well and our receive signal is 93 but we just can't get the pol/isolation right. It's not good enough that Bantel is comfortable with the numbers, but after hours of alignment of the polarization and tweaking the antenna alignment they give up.

One thing is we are not using the dish they supplied, instead we're using a bigger dish from a defunct satellite telephone system. It's a very professional and heavy duty Channel Master dish. The mount for the original outdoor equipment on the arm of the dish would not accept our satellite internet outdoor equipment so I adapted it, taking care to put the satellite internet outdoor equipment in the same position and plane as the original outdoor equipment was. During the pol/isolation alignment I even tried moving the alignment of the outdoor equipment which brought no improvement.

It sounds like the only possible causes for not being able to achieve good pol/isolation would be obstructions (none) or a defective BUC and/or feed horn, water in the feed horn/wave guide or a problem with the outdoor equipment not being perfectly aligned with the dish (bent arm etc).

We have the dish Bantel supplied with the system still in the box.

What would folks suggest? What would you suspect is the problem.
Could it be a defective BUC (a mechanical or electrical failure)? To me it seems like it couldn't be the BUC because the radio waves coming out of the BUC can only be one polarity in order for the waves to travel through the waveguide. I don't believe arbitrarily polarized radio waves could travel through the rectangular waveguide. If it was a round waveguide then yes. The outdoor equipment is in perfect condition, no cracks, no water in the waveguide etc. Could the problem be the antenna we're using?

Any suggestions or information would be greatly appreciated. Thanks! Greg



grohgreg
Dunno. Ask The Chief

join:2001-07-05
Dawson Springs, KY

1 edit

Photos would help confirm this. But my first diagnosis is that your dish configuration is at fault. The HN7000S modem statistical analysis that produces the red/yellow/green status. But the baseline for this analysis is based upon use with a limited number of outdoor equipment configurations. It's pretty clear that your dish configuration doesn't fall into this category. Let's start with the "large" dish. By design, the bigger the diameter - the higher the gain. This is what is producing what ordinarily would be an excellent receive signal level (SQF) for a "regular" sized dish. The fact that your oversized dish is producing a large SQF number is then misleading. Usable, but misleading from the aspect of troubleshooting.

Again I'm diagnosing in the blind here, but I suspect - next - that you've mounted the TRIA (Transmit/Receive Integrated Assembly) incorrectly on the feedarm. The transmit signal is probably bouncing off the dish at an inaccurate angle to reach the satellite accurately. That factor alone is what produces good transmitter isolation numbers (the 30 and the 6) as viewed by the NOC. The large SQF number is just confusing the issue.

Best solution is simply to procure/install outdoor equipment that's actually compatible with the HN7000S. Short of that I suggest you ignore the SQF when conducting POL adjustments with the NOC. Concentrate on following their telephone advice in obtaining the best transmit isolation numbers possible at their end. This is an adjustment at your end that MUST be made in real time with an operator at the NOC. Once your transmit status is "green", the receive status will almost certainly remain "green". Maybe not a 93, but almost surely at an acceptable operational level.

//greg//
--
HN7000S - 98cm Prodelin/2w "pure" Osiris - ProPlus - G16/1250H - NOC:GTN - NAT 67.142.115.130 - Gateway 66.82.25.10 - DNS 66.82.4.12 and 66.82.4.8 - Firefox 3 - AV/Firewalled by NIS2011 beta


takoateli

join:2010-10-09

1 edit

grohgreg,

Thanks! I think something I wrote might have been misleading but I think you still accurately diagnosed our problem here.

When I mentioned the color of the status light during the test I was speaking of only when the NOC has us in the test mode to measure our isolation and that condition is normal (the status light being red in the test mode to indicate that the system is not ready, there is no network connectivity for the user. I believe the status light being red is solely because the unit is in the test mode and has nothing to do with the antenna alignment or any kind of problem with the system.). The point I was trying to make is that I'm in the jungle of Venezuela with no other means of communication (I left that part out). Instead of them being able to throw our modem into a test mode and leave it in the test mode and direct me in adjusting the antenna/polarizer by telephone, instead the process is the NOC has to put the modem in the test mode, read the isolation, bring the modem back on line to enable us to communicate, give me directions on what to do, I carry those directions out, let the NOC know I did it, they then test again etc etc. That the process of aligning the antenna is more difficult and time consuming because of our lack of other means of communication is extraneous to the problem and for the sake of simplicity and clarity I probably should have left it out. Same goes for the status light being red when the NOC is testing.

But I think you are right on about the antenna because it's the only thing that is not part of the original system. In fact it surprised me that our provider Bantel knows we're not using their antenna and given all the problems we're having getting good isolation that they haven't demanded we use their antenna. I think they're just a reseller and aren't too technical.

FYI I'm a retired shipboard radio electronics officer and ham radio operator.

I will be assembling their antenna and I'll try it and let you know.

A few more questions if I may. Could an electronically defective BUC cause the polarity to be skewed or not clearly defined? I think not.

Another question is if we improve our isolation might our performance improve? It's already not bad.

You can see a picture of our antenna at »gregihnen.me/my-work-in-cosh-2/s···net.html

Thanks!
Greg



grohgreg
Dunno. Ask The Chief

join:2001-07-05
Dawson Springs, KY
reply to takoateli

In two-way satellite internet connections, the single-most important factor is transmitter isolation. In most cases it's crosspol, but copol is equally as important. It's so important, that - if the modem doesn't detect an acceptable ACP (the HughesNet acronym for Automatic CrossPol) - it will not permit the commissioning process to complete.

So. Let's back up to something a little more basic. Has your modem successfully commissioned, and you're just trying to optimize? Or are you still in the throes of trying to finish the commissioning process?

I would not suspect BUC problems are contributing to your current problem.

Since you actually have what I presume to be a modem-compatible dish, I suggest ditching the thrown-together system, and starting over with the provider-supplied dish.

//greg//
--
HN7000S - 98cm Prodelin/2w "pure" Osiris - ProPlus - G16/1250H - NOC:GTN - NAT 67.142.115.130 - Gateway 66.82.25.10 - DNS 66.82.4.12 and 66.82.4.8 - Firefox 3 - AV/Firewalled by NIS2011 beta



dbirdman
Premium,MVM
join:2003-07-07
usa
kudos:5

He's sending these messages with his dish, so it has to be commissioned. From the information at his link it sounds like he's been using this dish for quite some time.

I'm not positive, but I think that the US Hughes operations may be the only satellite company in the world that has ACP (Automatic) cross-pol servers that reflect back to the customer end. Every other one requires that a technician on the other end analyze the signal. Very unusual to have to use the same connection to "talk" to the tech - normally it can be done in real time with a separate phone connection where verbal instructions and feedback occur. I can understand the frustration!
--
Motosat self-pointing dishes: 1.2-meter XF-3 on 105W or 121W, .74 meter G74 on 89W, SL-5 HD DirecTV|idirect 3100|Hughes HN7000S|Verizon UMW190 Air Card|1990 Blue Bird Wanderlodge Bus "Blue Thunder"|Author of hnFAP-Alert, PC-OPI and DSSatTool


takoateli

join:2010-10-09

1 edit
reply to grohgreg

Greg,

Thanks again!

Our system here is a little different. Normally the provider requires an installer perform the installation but because of my background and the distances involved and the difficulty of travel in this area the company allowed me to self install. But the procedure I follow is the same that their installer would do. Here's how the installation goes. One receives a system from the provider. One setup up the equipment and browses to the manual commissioning page of the modem where one enters in info about the site and the satellite used. Next one orients the antenna for best signal. Finally one contacts the provider and they run a test from their end to see the isolation/cross pol/copol and from their end they direct the installer to make adjustments to the polarization till it's adjusted properly. With this system there's no ACP.

Basically we're still in the process of finishing the commissioning. Things were good when we were on the Intelsat 903 satellite but a few months back we had to switch to Hispasat Amazonas II and on that bird we've never been able to get the polarization alignment up to par. We had gotten it to the point where they thought it was good enough. Then a week ago I wanted to reseal the connections on the LNB and BUC. When I was done for good measure I contacted the provider and had them check our polarization alignment to confirm I hadn't accidentally moved the outdoor electronics or the antenna. I was sure I hadn't but I wanted to be sure things were still good. They weren't acceptable so we began the alignment procedure again. Throughout this whole process during all the days we aligned the folks on the other end (the provider's techs) were surprised that there wasn't much change as we rotated the polarization adjustment. If we move it a lot it get worse, but there isn't the clearly defined null or peak there should be in the middle.

I'm in the process now of setting up the new antenna.

Here's what my modem looks like on the transmitter->acp page

ACP Stats

------------------------------------
Network Time: SAT OCT 09 23:38:00 2010
------------------------------------
ACP Server Status : ACP is currently not required

ACP Server Version : Non-regional ACP
Installer ID sent to Server :
Remote's Longitude and Latitude : 65.2W / 3.0N

---------------ACP Statistics--------------

Last Validate Isolation..... 0 Last Revalidate Isolation... 0

Pointing Queue Full......... Yes Pointing Queue Depth........ 0
Validate Queue Full......... Yes Validate Queue Depth........ 0
Revalidate Queue Full....... Yes Revalidate Queue Depth...... 0

User XPOL Pointing Requests. 0 User XPOL Validate Requests. 0
Self XPOL Validates......... 0 Self XPOL Revalidates....... 0
NOC XPOL Validates.......... 0 NOC XPOL Revalidates........ 0
XPOL Validate Pass.......... 0 XPOL Validate Fail.......... 0
XPOL Revalidate Pass........ 0 XPOL Revalidate Fail........ 0
XPOL Backoff................ 0 Time (s) Since Pass XPOL.... 0

Minimum Revalidate Interval. 0 Maximum Revalidate Interval. 0
Short Random Backoff........ 0 Long Random Backoff......... 0

Queue Indications........... 0 Queue Indication Discards... 0
Testing Allocations......... 0 Testing Allocation Discards. 0
Measurement Results......... 0 Measurement Result Discards. 0
Directed ACAPs.............. 0 Total ACP Requests.......... 0
Subsystem State............. 0 Test State.................. 0
XPOL Revalidate Timeout..... 0

---------------Last ACP Validate/Revalidate Statistics--------------

Last Validate Timestamp..... Last Revalidate Timestamp....
Last Validate Isolation..... 0 Last Revalidate Isolation... 0
Last Validate SQF........... 0 Last Revalidate SQF......... 0

Thanks!
Greg



grohgreg
Dunno. Ask The Chief

join:2001-07-05
Dawson Springs, KY

1 edit
reply to takoateli

I understand, I've helped quite a few of our armed forces personnel set up under similar conditions over in the Middle East. That's via the other forum you posted to earlier.

Don't waste any time on that modem ACP page. Without an ACP server at the NOC, it's useless. I know it says isolation, but that's a red herring. ACP (Automatic Cross Poll) is Hughes proprietary name for the automatic feedback system that helps optimize transmitter isolation. There are no measures in place for manual isolation data to show up there.

I believe things will come together for you once you get a dish set up that's a bit more in line with the modem capability and limitations.

//greg//
--
HN7000S - 98cm Prodelin/2w "pure" Osiris - ProPlus - G16/1250H - NOC:GTN - NAT 67.142.115.130 - Gateway 66.82.25.10 - DNS 66.82.4.12 and 66.82.4.8 - Firefox 3 - AV/Firewalled by NIS2011 beta


takoateli

join:2010-10-09

Thanks! I just assembled the antenna. I have to take a trip tomorrow to the nearest town (la Esmeralda) and do some stuff. I should be gone for a few days. When I get back I'll set up the antenna and check it out, and of course I'll post the results here.

Greg


takoateli

join:2010-10-09

Everyone thanks for the comments. I once again have learned a lot from the helpful and knowledgeable folks on a forum.

An update. I installed the provider's dish and alignment was fast and simple. I tweaked up the antenna for the highest signal, and with three turns of the polarization we achieved a cross pol of 30 and they said "lock it down". The system is running better than before.

The previous antenna was left over from a now defunct satellite telephone system. The antenna is a very large and professional Channel Master. I tried our satellite internet provider's outdoor electronics with the feed horn from the old sat tel system so I know the feed horn was right. Tried using the feed horn supplied by the sat internet company and it made no difference. I know I had the outdoor electronics/feed horn very close to where it should have been if not perfectly where it should have been. But what ever, we just couldn't get the cross pol right. Not only that the response from turning the polarization adjustment wasn't responsive. Across a wide range they'd say there was no change (still bad) and finally when it was really far one way or the other it would get worse. With the right antenna the response was immediate and it took just three attempts to get it right. Since we have no other comms here they would have to test our cross pol, bring us back on line, tell me what to do, I'd confirm the movement, and they'd test again. It was a slow process. But now finally it's really good.

Thanks to all who commented! You guys are angels.

Greg



dbirdman
Premium,MVM
join:2003-07-07
usa
kudos:5

Glad to hear you got is working! Hughes equipment really is unique, so it is always hard to get things right with assemblies from different setups.