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W3A Camp Taji HX alignment / signal issue

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Mar 1st, 2009 at 10:30am  
I am on Camp Taji Iraq trying to lock on to the w3a. my dish was previously used on another satelite 5 days prior using a Hughess 7000 series modem. we switched to Bentley Walker and they shipped me a HX50 modem and new LNB which I have already installed. I verified my Az/El with a Sutto clineometer/compas combo, but have not been able to lock on. yesterday I was peaking a signal at 29%. today I've only been able to peak at 15%
any thoughts?
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« Last Edit: Mar 1st, 2009 at 1:16pm by Admin1 »  
 
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Eric Johnston
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Reply #1 - Mar 1st, 2009 at 1:08pm  
Antenna pointing and polarisation angles:
Calculate the azimuth (magnetic compass), beam elevation and polarisation angles using Satellite dish pointing Iraq.
Expect a result like this below.
...
Fine adjust to your exact location and the blue line will help you with azimuth angle.

Elevation angle:
Use the elevation scale on the bracket.  If no scale then tell us the make and model number of the dish and maybe send a photo of your dish (to eric@satsig.net), taken with the camera exactly sideways and in line with the front face side edges of the dish.

Polarisation angle:
You will have been told the name of your downlink polarisation.  Probably polarisation name=Horizontal.
Setting the polarisation angle is a two step process.
First step is set to nominal polarisation:  For Horizontal polarisation the broad faces of the LNB waveguide must be on either side, so set the LNB side arm sticking upwards.
Second step is apply the calculated adjustment angle plus 3.5 deg: e.g. + 42.4 + 3.5 = +45.9 deg.  While facing towards the satellite turn the feed/LNB/BUC assembly 46 deg clockwise.  Since you have an inclinometer try putting this sideways across the BUC body, and tilt 46 deg to the right.  (Reason for adding 3.5 deg is that Eutelsat W3A was constructed with +3.5 deg clockwise offset)

With the above set you should be able to swing the dish and the HX modem will lock up blue as you past the satellite. Set to the middle of the range between the blue lock points in az and el. Peak up to the very best 1% you can get.  It should take at least 30 minutes to peak up.

HX Modem
I guess you have already set the various parameters provided to you by Bentley Walker.  The frequency and symbol rate are important.

Best regards, Eric.
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Reply #2 - Mar 2nd, 2009 at 6:29am  
Eric:

Thanks for the help. The az/el you sent me were almost exact, I have attempted again today to zero in on a signal and the best I could get was 17% this time but the signal was almost 2 degrees from what the modem called for. Also I dont know if this is a factor yet but I have not connected my transmit cable to the modem. does that play into the aiming process?
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Eric Johnston
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Reply #3 - Mar 2nd, 2009 at 10:25am  
Polarisation:
...
This is correct for horizontal receive polarisation with about +46 deg clockwise adjustment applied.

I can see here on my spectrum analyser your very high power wanted carrier on W3A at 10877.2 MHz, so it does exist.  Horizontal down. 13 Msps. Your modem tuning is all correct:  Modem 1127.2 MHz + LNB LO 9750 MHz = 10877.2 MHz satellite.  11272 (100kHz) = 1127.2 MHz.

Elevation scale:
...
The front face of the dish is tilted backwards slightly.  This is consistent with an offset angle of about 30 deg plus about 5 deg backward tilt of the front of the dish, giving a beam elevation angle of 35 deg.
The bolt with the washer is assumed to be the reference mark in this case.  In some antennas the metal edge visible through the slot is the reference mark.
To adjust the elevation, loosen both elevation axis bolts, loosen both slot bolts and get someone to gently push upwards on the end of the feed arm while you turn the adjustment bolt. It is otherwise easy to strip the thread on or break the adjustment bolt.
The setting on the elevation scale will be wrong if the pole is not upright, if the pole clamp is loose or the azimuth head unit hold down bolts are loose.  All these are apply while setting up and you will need to try higher elevation setting angles to find the satellite. Go up in 2 deg increments.

Once you have found the satellite peak up the azimuth first. When you tighten the azimuth hold down bolts and the pole clamp the elevation will rise and you will probably lose the satellite, but you will find it again with the elevation adjuster.

Please tell me the model number and other text on your Invacom LNB.  I am assuming it is has 9.75 GHz LO frequency with 22kHz tone off, but want to check.

Always power off at the AC power mains switch before connecting or disconnecting the coax cables.

If you get a 17% reading when you find a satellite have you peaked up on it ?  Your pole clamp is not tight and head unit is sagging down, so you will need to set a higher elevation on the scale to find the satellite.  Peaking up will require about 30 minutes of tiny adjustments.  Turn the elevation adjustment bolt in 1/6th turn increments and record the % at each position. Wind the elevation both right across the beam and then wind back to the middle. It is not so easy using the azimuth adjuster (if there is one) as there is backlash.

Leaving the transmit BUC coax cable disconnected at both ends while dish pointing is a good idea since it stops premature transmissions.

Best regards, Eric.
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Reply #4 - Mar 2nd, 2009 at 12:24pm  
Eric

the Invacom Part number is SPV-30SM
LO 9.75/10.6GHz

i have located a satellite at 230.5 az on my location. I have peake the signal to 29% but it wont go any farther. i even swung the feedhorn to -46 degree with no effect.

the other issue i am plagued with is the elevation. both my inclineometer and the scale on the side of the dish show the elevation to be around 43 degrees
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Reply #5 - Mar 2nd, 2009 at 2:15pm  
Hughes SQF (received signal level) numbers  below 30 typically represent noise. Same applies to signals detected by most satellite signal meters. To demonstrate, simply point your dish at the sun and see what kind of "signal" level is produced. And if get SQF indications or meter deflections at 43 degrees elevation - from anywhere near your latitude - it's almost certainly noise. W3A viewed from ANYWHERE in Iraq can only be seen inside an elevation window of  roughly 32 to 38 degrees.

If it's not noise you're detecting, is there perhaps a design offset angle that you should be considering in your elevation calculation? And are you considering magnetic deviation when setting the azimuth angle by compass?

//greg//
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Reply #6 - Mar 3rd, 2009 at 7:59am  
design offset angle? not sure what your talking about.

as far as the azmuth goes im fairly certain im lookin in the right spot.  i have also swung the elevation to the low and highest point. the entire signal dissapears except for the one spot. the elevation indicator on the mount has the center of the bolt head going through the 44 degree slot.
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Reply #7 - Mar 3rd, 2009 at 8:14am  
Quote:
the Invacom Part number is SPV-30SM
LO 9.75/10.6GHz

That is the correct part.  With 22kHz tone OFF the LNB local oscillator will be 9750 MHz which is correct. All this is correct:  Modem 1127.2 MHz + LNB LO 9750 MHz = 10877.2 MHz satellite.  Note 11272 (100kHz) = 1127.2 MHz

Quote:
i have located a satellite at 230.5 az on my location. I have peake the signal to 29% but it wont go any farther.

It is highly likely that you are finding the correct satellite.  The maximum reading of 29% is significant.  It means you have found a powerful signal but that the signal is not locking in the HX modem due to some mismatch in the configuration parameters or wrong satellite or wrong polarisation.

Quote:

the other issue i am plagued with is the elevation. both my inclinometer and the scale on the side of the dish show the elevation to be around 43 degrees

The calculated beam elevation angle was 34.4  so the angle on the elevation scale should be similar.  An error of several degress is not unusual, depending on the uprightnesss of the pole, the tightness of the pole clamp and the tightness of the azimuth hold down bolts.
With eveything a bit loose the scale reading will be 2 to 5 degrees high, but not 9 deg error.

You say that your scale shows 43 deg using the bolt as the reference.  What reading do you get if you use the upper edge of the metal plate that the can see through the slot, as the reference.

You say that your inclinometer shows 43 deg.  How did you do that ?  An inclinometer applied to the front side edges of the dish should read about 13 deg if the offset angle of the dish is 30 deg.  Do you know the offset angle of the dish accurately from the manual ?

Best regards, Eric.
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Reply #8 - Mar 3rd, 2009 at 8:22am  
Thanks Eric

im still not getting above 29% signal though
Joe
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Reply #9 - Mar 3rd, 2009 at 8:28am  
29% is a special number.  It is the maximum reading that is possible when the dish is pointed at a strong signal that does not match the parameters in the modem.

You have tried the polarisation at both +45 deg clockwise and -45 deg anticlockwise, as viewed looking towards the satellite.  The +45 deg clockwise, as per the picture above is correct.  There is a carrier on the opposite polarisation so some reading between 0 and 29% should be seen on the wrong polarisation setting.

I'm inclined to check the modem configuration again but need to have my breakfast and take the dog for a walk just now.  I'll think about it while I'm out.

Where you are looking, there are satellites in a diagonal 45 deg line across the sky.  What do you detect if you come down a couple of degrees in elevation and go right 2 deg ? etc.

Best regards, Eric.
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Reply #10 - Mar 3rd, 2009 at 9:06am  
Eric:

you take care of your business, i completeley understand.

and yes in the photo i sent you at that position i can get no greater then 28% when i flip the LNB to -46 degree i can get 29% . The settings that BW sent me was for a recieve polarization of vertical, transmit  is horizontal

also something that has me curious, when i removed the old LNB there was a diapole inside the rectangular area. The new LNB does not have one visable. Is this something i should be concerned about

one more thought to ponder. i was previously under service with ATS Iraq, they actually did the install. the modem they issued me was a Hughes 7700. i am wondering if the radio unit is not compatible with the HX 50 modem?
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Reply #11 - Mar 3rd, 2009 at 9:28am  
It does not matter that the dipole pin in the Invacom LNB is not visible.  It has a front end filter.  The polarisation is still at right angles to the broad faces of the rectangular waveguide.  When the LNB side arm is directly upwards that is the nominal Horizontal polarisation starting position.

The Bentley Walker document regarding polarisation may be wrong.  What text you set in the modem is irrelevent for your set up.  The modem cannot change the polariation, which in your case is the physical rotation of the feed assembly by hand.  I can see your wanted carrier here and it is Horizontal down.

Please contact Bentley Walker regarding modem type and if it is suitable.  I thought you had an HX model.

Best regards, Eric.
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Reply #12 - Mar 3rd, 2009 at 11:30am  
Ok ill contact BW

I now know beyond a shadow of a doubt that i have the correct satellite. I re-installed the original LNB and re connected the 7700 modem. then i powered it up and swung the dish back to the Az/El provided by the modem. within 2 minutes i had a 95% lock on to the W1 satellite. so with that in mind i changed everything back  out to un the HX 50 swung the dish back 3 Degrees and powered up, again 2 minutes later i locked in 29% signal
so i either have a bad part or a bad setup
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Reply #13 - Mar 3rd, 2009 at 3:29pm  
Sir,

I am following the case and ready to assist you at your convenience.

Please email me james@bentleywalker.com for further assistance.

Regards,

James - Bentley Walker.
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Reply #14 - Mar 5th, 2009 at 2:20pm  
Everyone:

folks i am back to square one again. i got my hands on a satellite finder only to confirm my previous assumption. I am locked onto W3A. However the HX 50 modem is only giving me 29% as usual.

any other ideas?
help.......
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Reply #15 - Mar 5th, 2009 at 3:03pm  
Still "could" be a bad modem. But it's sounding more and more like you got the wrong satellite parameters from the provider. The modem user interface (registration section) must be set up letter perfect: modulation type, coding rate, symbol rate, transponder frequency, et cetera. To be fair, you could also have been given the correct parameters - and simply entered one of them incorrectly. Either way, all these parameters and more are critical for the modem to recognize - and process - the signal it's being fed.

//greg//
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Reply #16 - Mar 5th, 2009 at 3:12pm  
The customer is now liasing direct with BW for troubleshooting. Thanks to all for their feedback, we would like to avoid confusion arising from multiple diagnosis so will take it from here.
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