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Locating AM 22 from Iraq

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Ex Member
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Nov 2nd, 2006 at 4:14pm  
Hello All,

We are trying to find AM22 at 53E, using a 1.2M Andrew dish and equipment bought from Bentley Walker.  They sent us a Horizon Satillete Meter, to which we downloaded the AM22 data from the website.  We also have software i-Direct (I think it's called) that is also supposed to help us find, lock and peak the signal.

We are using the following data based on the calculator this forum website provides for our location at 34.62N and 43.70E:
159.63 dish azimuth (magnetic)
48.56 degrees elevation
-13.17 polarisation

We have our sateliite mounted on a completely vertical mount.  AM22 calls for horizontal polarisation, and I believe we are set that way.  However, does horizontal polarisation mean that the LNB and BUC are turned sideways rather than up and down?  We have ours up and down.  The instructions we have are confusing on this point, but I think I read a comment by Eric saying it is up and down.   I also verified that we do not need to take into account offset on the dish - they built that into the scale on the mount already, or so they say.

The default dB level on the meter is 54 when we turn it on.  We are able to get about 73-75dB on the Horizon meter when we get on the proper the azimuth and elevation, but never more and never a lock.  The "searching" text on the screen never goes away.  We make small movements left/right and up/down to try to peak the signal, but it never gets any higher no matter what we do.

The reason I have been the term "we" is because there are two of us with the same systems trying to lock onto AM22.  We have read most of the postings on dish alignment here, and  realize it is a tedious process.  Despite our best efforts, we cannot lock onto the satellite.

Do you recommend that we use the Horizon handheld meter or use the software on the computer to fine tune and try to get a higher signal and a lock?  The thing we're concerned about is that we can't even get it to lock on -- the "searching" text never goes away.  We're wondering if we might have a hardware problem.  Any help would be much appreciated.  We are going on about 15 or so hours of searching without any luck.  Thank you very much.
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Eric Johnston
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Reply #1 - Nov 2nd, 2006 at 7:11pm  
Polarisation:

Your receive downlink polarisation is named "horizontal", but this does not mean that it will be actually horizontal.   That would only happen if you were on the same longitude as the satellite.

The procedure is to initially set the polarisation to real horizontal and to then to rotate by the required angle.

Note the rectangular waveguide going into the small LNB receive module.  For horizontal polarisation the broad faces will be on either side, like so:
...
Set that as the initial starting position.

Now adjust the polarisation.  While FACING TOWARDS towards the satellite, turn the feed assembly 13 deg anticlockwise, i.e. the top to the left, like so:
...
Don't tighten up the feed throat clamp too tight, the NOC may ask you to crawl under the feed arm and reach up to turn the feed assembly 1 or 2 degress either way to get you into the exact cross-pol null.  The rotation must be set to 1 deg accuracy.

Horizon type meter.

The meter works initially as a total noise power meter.  It will give higher readings whenever it sees any satellite, or even the warm ground or the sun.  So you can use it to peak up accurately on anything - without any programming.  In this mode you don't know which satellite and you might easily peak on the wrong one.  In your case the satellites are in a gently sloping line going down towards south east.  ( If you point round to near south you would find several satellites in a more or less horizontal line. )

The meter is programmed to recognise the approx frequencies and symbol rates of satellite carriers and to announce a satellite name.   Unfortunately the way this is done is a secret so you can't  check that the correct carrier frequency and symbol rate are pre-set.   I don't know what carrier it has been programmed for and can't say if that carrier is even present in the L band cable from your LNB.  It depends on the polarisation and the local oscillator conversion frequency of your particular LNB.  Unless they have programmed it with the characteristics of a carrier on horizontal polarisation on SESAT and done thier calculations using your particular LNB local oscillator frequency (e.g. 10 GHz or 11.3 GHz) then it will never lock at all.  Don't worry too much.  You have a very good peaking up aid.    If you think you are on the wrong satellite try up a bit and to the right, also try down a bit and to the left, to investigate the two adjacent satellites, on either side.

Bentley Telecom have three alternative iDirect services on SESAT and they use a mixture of horizontal and vertical polarisations and also low and high local oscillator frequency LNBs - so there is a 66% chance that your Horizon programming won't work for your LNB frequency and horizontal polarisation.

Regarding the iDirect modem.

This must be pre-configured with the downlink frequency and symbol rate etc.  With this it should lock up on the carrier and give out green light, and volts (I think).   To get the transmit side working I think you must also tell it your latitude and longitude.   I have not done this, so read the instructions.

My feeling is that with the iDirect modem suitably configured you should boldly swing the dish once and the green led will come ON for a while.  Set to the middle of this ON range, repeat for elevation, counting the turns of the bolt and wind back to the centre of the beam.  If you miss the satellite, raise the elevation a bit and try again, since when the main pole clamp is loosened the elevation tends to sag down several degrees.  Do the final elevation tweeking after you have tightened all azimuth clamp bolts.

Good luck.

Best regards, Eric.
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Reply #2 - Nov 3rd, 2006 at 7:54am  
Eric,

Many thanks for the advice.  I believe we are setting the polarisation correctly.  We'll double-check based on your advice.

From you are saying, I am now skeptical as to the accuracy and helpfulness of the meter.  We will try with the software instead.  I believe we have that loaded with the correct data, as you suggest.  We have not used it much yet, so we will try that now.

I also susepct from you say that we are not on the right satellite.  Again, from what you say, I think perhaps the i-Direct modem is the better way to find this thing.  The meter has never given us any indication that we are on the right one.  But, at the same time, it seems that we are only picking up one satellite.  Perhaps my elevation has been incorrectly set.  From what I have seen you write in many other postings, it seems that this is the most crucial setting (as well as polarisation I guess).

Thanks again.  I will reply when we find it to see what we were doing wrong (hopefully no more questions - but we'll see).

Thanks, Troy
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Eric Johnston
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Reply #3 - Nov 3rd, 2006 at 6:34pm  
The meter is probably programmed with some arbitary TV carrier on AM22.   You could try briefly turning the feed 90 deg for vertical polarisation and see if the meter announces ""SESAT AM22".   If so you are on the correct satellite, just turn it back to horizontal polarisation for your iDirect operation.  If this fails it does not prove it is the wrong satellite however as the meter programming may have assumed a 11.3 GHz LNB rather than 10 GHz LNB.

As a power meter it is good for peaking up the azimuth and elevation - any satellite.  The readout works well and it is not too difficult to halve the beam peak and get to the exact centre.

If you have problems with elevation, send a close up picture of the scale and also a view of the dish and feed arm from the exact side view with the camera at the same height as the dish and in line with the front edges.  i.e. a true side view.  eric@satsig.net

Read and see pictures here also
http://www.satsig.net/cgi-bin/yabb/YaBB.pl?board=point;action=display;num=116074...

Best regards, Eric


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« Last Edit: Nov 4th, 2006 at 12:28pm by Eric Johnston »  
 
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Reply #4 - Nov 10th, 2006 at 11:58am  
Eric/All,

Thanks for your help.  We finally got on using i-Site.  Turns out the meter we were using just never told us we had a lock like the instructions said it would.  So we didn't think we had actually found the satellite (or gotten close enough), when it turns out we had.

I recommend to anyone having problems out there to use a meter for initially finding the satellite.  After that, switch to software that will help you to peak the signal.  In our case, we actually ended up turning on i-Site, only to find out we were dead on the satellite.  No further peaking was required at all.  We simply called the NOC at Bentley Walker, they did some configuring, turned it on, and we are up and running.

Thanks again for the help, Eric.  This is a tremendous resource for do-it-yourself satellite work.

Troy
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