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VSAT technology and installation >> HughesNet and Hughes HX VSATs >> Andrew dish assembly and polarisation setting https://www.satsig.net/cgi-bin/yabb/YaBB.pl?num=1171834727 Message started by VbGuy on Feb 18th, 2007 at 9:38pm |
Title: Andrew dish assembly and polarisation setting Post by VbGuy on Feb 18th, 2007 at 9:38pm Quote:
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SNR is the signal strength, but 8 is very low it has to be 14 at least . Quote:
I am in good coverage place . My iDirect 3100 Modem working very good . Quote:
I need your help here to make sure everything is ok. here is my numbers for Long and lat : latitude=31.9249, Longitude=12.2538 Lat = 31 degrees, 55.5 minutes North Long = 12 degrees, 15.2 minutes East Dish elevation = 32.7, Azimuth=120.7, Polar=-46.3 I got them from this page : https://www.satsig.net/maps/lat-long-finder.htm My location is : Latitude (Deg N) : 31 Degrees 55 Minutes 29.46 Seconds ------------------------------------------------ Longitude (Deg E) 12 Degrees 15 Minutes 13.60 Seconds satellite is AM22 53E Can you please give my picture of correct position of LNB & BUC . The technical man got the sat using (sat looker) but the signal still weak ... |
Title: Re: Polarisation adjustment Post by Eric Johnston on Feb 18th, 2007 at 11:08pm
Polarisation: The required adjustment is a feed/LNB/BUC rotation movement of (minus) -46.3 deg anticlockwise, while facing the satellite.
I don't know your correct nominal polarisation starting position, horizontal or vertical. Did they tell you nominal horizontal or nominal vertical (downlink receive)? The definition of the nominal vertical starting position is with the rectangular LNB input waveguide with its two broad faces on top and underneath. There are two alternative vertical polarisation start positions, with the LNB arm sticking out on the left or the right side. If you still have the feed polarisation set to a start position, either horizontal or vertical, your signal will be -3 dB down and you may be suffering severe interference if there are signals on the opposite polarisation. The measurement level may increase whenever the dish points at any satellite. Once the correct satellite is detected the RX LED should change from yellow to green, and the measurement value increase further (above 12) in the iSite screen. Once you have found the satellite, I believe it is important that the lat and long coordinates are correct. Best regards, Eric. |
Title: Re: Andrew 1.2m dish polarisation and focus Post by Eric Johnston on Feb 19th, 2007 at 12:19pm
Your polarisation setting corresponds to nominal vertical polarisation, rotated by (minus) -46 deg anticlockwise while facing the satellite.
This is correct. The elevation scale is reading 50 deg. It should be 32.7 deg. This is weird since you say you are now successfully accessing the internet. Does your iDirect have green RX led ? Please take a side view photo, with the camera in line with the two front sides of the dish and all of the mount, dish and LNB etc visible. Hold the camera level so the background is horizontal. email the picture to me eric@satsig.net if you wish and I will link it in. It is not clear in your picture where the feed support yoke is attached to the boom. Perhaps your feed is about 6 inches too far away from the dish ? This would explain everything: Out of focus axially and upwards of the focal point = Low gain + low gain + poor cross pol isolation. Upwards of focal point = wrong elevation reading. If it is like this, the bracket attaching the feed support arm to the bottom of the dish will be almost breaking the plastic as the arm is pulled upwards too far ?. Don't drop the arm if you need to change things. Get someone to hold it. Does it look like this: Best regards Eric |
Title: Re: LNB/BUC/Feed yoke to arm assembly Post by Eric Johnston on Feb 19th, 2007 at 3:08pm
The attachment of the feed support yoke to the arm is completely wrong. It is attached at the end of the arm. It should be near the bend in the arm. See my RED line drawing.
Re-assemble like this: Get someone to hold the arm while you reposition the two bolts into the pair of holes nearest to the bend in the arm. After you have moved the bolts the beam elevation angle will really be 50 deg so you need to readjust the elevation down to 32.7 deg. You will find the satellite when the scale reads 32.7. The scale will now read the correct angle. Best regards, Eric. |
Title: Re: poor SNR in AM22 Post by VbGuy on Feb 19th, 2007 at 8:15pm
Thank you for the great assistance Mr. Eric Johnston .
I will do exactly like what you said, also I got new dish from the same type as seen above . I can aver that the reason for the wrong angle is the wrong place for the feed support yoke . I will do that tomorrow morning cause the weather now very bad here (so cold) . Thanx alot |
Title: Re: poor SNR in AM22 Post by VbGuy on Feb 20th, 2007 at 11:32am |
Title: Re: Andrew dish assembly and polarisation setting Post by Eric Johnston on Feb 20th, 2007 at 1:17pm
You are welcome
This is the final image of the Andrew 1.2m antenna set for elevation angle of 32 deg. The nominal receive polarisation was vertical (starting with the LNB sticking out on the left side). The polarisation adjustment required was -46 deg, i.e. minus, anticlockwise rotation of the feed while facing towards the satellite. Do you want your imageshack images stored here permanently ? Best regards, Eric. |
Title: Re: Andrew dish assembly and polarisation setting Post by VbGuy on Feb 20th, 2007 at 1:45pm
Mr.Eric Johnston Thanx alot for the modification ...
You can freely do what you need with images it's now belong to every one in this great forum,especialy you cause you the hero of solution ... Thank you again for your great advice and step by step guide .. I will never forget you ... |
Title: Re: Andrew dish assembly and polarisation setting Post by koloman on Mar 7th, 2007 at 6:28pm
Hi ALL.
i have a serious problem on my site i just lost two set of modem within a week. what i noticed is that the modem Rx side does not give me good signal voltage,the best i could get is about 8volt which is very abnormal. i finally took my LNB to test in another site and it was working perfectly.i also tested the modem there and it was not working up to the right volt.i believe this must have been i am having a damage cable which i did not noticed in time that have result in me loosing my modems i try entring the modem but its not accepting the general password and even when i try using the console cable, the area where i am suppose to apply USER NAME & PASSWORD is not accepting any carracter (letters). please do any one have solution for me or what best to do.i believe i have to ship my modems (3) back to the factory (iDirect) but i dont know how to go about this. please give me good informaton on how to fix my modem, who to contact, how much will it cost me, how long will the repair take before sending them back to me and how to apply for this cos i can not afford to loose 3 modem just like that.i need your helps all. thanks. kayode (Nigeria) |
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