SatSig topic:

HX 50 dish pointing - HELP

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Jan 31^st, 2009 at 6:52pm

For some reason I cannot get connected to W3A

I am hooked to the LNB, which is pointing directly away from the mounting arm, the Feed horn bump is pointing towards the mounting arm with feed horn 5-0-5 and notch pointing away from the feed arm. the skew of the LNB to cradle is 0.

My settings are as follows:
Elevation 33.5
Azimuth (mag) 236.6
Pol 47.8

I have set the pol by rotating the dish on the mount 48 deg clockwise as looking from the rear.

I have set the elevation to 33.5 and swept the entire horizon several times, with the strongest signal being 75 on my Horizon meter (which is set to W3A Europe 10G). The horizon meter never locks on.

So I rotate the dish to 0 skew. Repeat, get 75 again, no lock

So I rotate the dish to -48 deg skew and sweep again. Still no lock but signal of 75.

So I rotate the skew back to +48 and set the azimuth to 236 and sweep the elevation. I find several signals, but no lock.

Finally out of frustration, (after 2 hours) I spend the last hour starting at 15 deg inclination and sweep the horizon 1 adjustment nut turn at a time until 45 deg inclination. Never did achieve a lock.

I know the horizon meter works, as I tested it on the old dish set to W1.

Anyone have any ideas?

Thanks

Thomas

Feb 1^st, 2009 at 9:02am

Most likely the Horizon meter is not programmed correctly for W3A and your polarisation and your LNB local oscillator frequency. You could try to get an updated file for the Horizon meter, but the file MUST have been made by someone who knows the polarisation you are using and the LNB local oscillator frequency you are using and details of an existing satellite TV carrier within the range of your LNB local oscillator frequency.

On W1 the meter had correct programming to find a known TV carrier on W1 satellite and the programming matched the polarisation and the local oscillator frequency you were using.

The Horizon will always act as a sensitive power meter and help you peak up on any satellite.

If you get a distinctive peak on a satellite (but no lock) then change over to the HX modem and see it that locks up. The HX modem, like the Horizon, first needs a frequency and symbol rate configured for the wanted carrier. The Modem will lock to the wanted carrier.

Best regards, Eric.

Feb 1^st, 2009 at 9:17am

I will recontact BW and see if the can send me the updated horizon files.

I went out this morning again with compass and inclinometer, and could not find anything but background noise within 6 adjustment rotation plus or minus on both the azimuth and elevation settings.

I did try with the modem, and could not get it to lock to any of the peaks I found. I will wait until I get the updated files

Thanks

Feb 1^st, 2009 at 9:51am

If you tell me the frequency and symbol rate of your downlink carrier and the name of the downlink polarisation I will check it here on the spectrum analyser.

Best regards, Eric.

Feb 1^st, 2009 at 1:15pm

Sat W3A

Sat Longitutde 7 degrees east
Sat Frequency 11272
Symbol Rate 13000000
LNB 22KHz switch Off
DVB Mode DVB S2 ACM
Frequency Band KU/QPSK
Receive Pol Vertical Horizontal
Transmit Pol Horizontal Vertical

Thank you

Amended by Eric 2 Feb 2009 1152G

Feb 1^st, 2009 at 1:59pm

Amended 2 Feb 2008 1134G

If you are trying to receive Horizontal polarisation name...

You have assembled your feed so that the LNB is away from the feed arm. With the feed arm at the bottom this is the starting position for Horizontal receive polarisation.

(note that fat lump on the horn throat must always be directly towards the feed arm under all circumstances).

Now apply the +48 deg adjustment; rotate the dish by an amount of +48 deg clockwise, as viewed with you behind the dish and facing forwards towards the satellite.

Your wanted carrier definitely exists. I can see it clearly with a 80cm dish.

using my on line satellite spectrum analyser You need to email me for help to see Horizontal as the default is Vertical. There is a 2 MHz error in my LNB LO freq during this cold weather.

The 13 Msps wide carrier has frequency 1127.2 + 9750 = 10877.2 MHz on Vertical name downlink polarisation. You need an LNB with local oscillator 9750 MHz (e.g. switchable type but not switched up to 10600 MHz)

For elevation this might help

For 33.5 deg elevation set the distance to 26.5 cm. There are errors here if the central bolt is not yet tightened down. So try up a bit.

The proper way (see below) is to put an inclinometer against the side of polarisation scale. This circular plate is at right angles to the beam, regardless of polarisation rotation.

Note this is in Afghanistan with an elevation angle of 48 deg set accurately.

References:
Setting elevation angle Prodelin 1.2m HX dish using tape measure
How to make an inclinometer

Best regards, Eric.

Feb 1^st, 2009 at 2:59pm

Great. I am still trying to figure out. BW had me do 48 deg clockwise polarization as I was looking at the satellite. (clockwise from the back).

Thanks

(edited by Eric 2 Feb 2009 1138G)

Feb 1^st, 2009 at 4:16pm

(Amended by Eric 2 Feb 2009 1142G)

With LNB away from the feed arm and the feed arm at the bottom that is true Horizontal.

Polarisation is the direction of the dipole antenna pin inside the LNB input waveguide. If the broad faces are on on either side that is horizontal polarisation, like so:
Horizontal =

It does not matter which side is the pin, either way the electric field is horizontal.

You then apply your +48 clockwise adjustment, starting from a correct name start position.

Horizontal name polarisation with +45 deg clockwise adjustment applied.

Best regards, Eric.

Feb 2^nd, 2009 at 10:41am

I have verified with BW that the W3A for HX50 from Iraq is:

Receive Pol Horizontal
Transmit Pol Vertical.

The sheet they sent me was backwards.

My LNB should be in the proper position with 48 Deg + skew (clockwise if looking from the back)

They are sending me the horizon data files again to ensure that I have the proper ones to obtain a lock.

Will update

Feb 2^nd, 2009 at 2:02pm

Sir,

Just checking if you have recieved the updated file from my colleagues and if you need further assistance.

James - Bentley Walker

Feb 2^nd, 2009 at 8:41pm

Yes, I got the files, thank you. BW helped me determine that a strength of 69 dbu was not enough to have the Horizon meter lock on. I plugged it into the modem, which did lock once it was set to horizontal.

Now, when I peak up the highest I can get is 83-89 on the modem, and about every 30 sec to 1 min, it will lose lock, lock to something else for a split second, drop transmission, state "Transmitter is not locked to network timing (TxCode 5). Then about 5 seconds later it will lock again.

I will do this over and over again. I thought it was a polorization issue, so I both increased and decreased the dish rotation by 1-2 deg per try and then would attempt to repeak. The only one which will peak in the 80's is the one which will keep dropping lock (48 deg clockwise from the back).

Ideas?

Feb 2^nd, 2009 at 11:11pm

soundtek86 wrote
Quote:

Now, when I peak up the highest I can get is 83-89 on the modem, and about every 30 sec to 1 min, it will lose lock, lock to something else for a split second, drop transmission, state "Transmitter is not locked to network timing (TxCode 5). Then about 5 seconds later it will lock again.

It will do this over and over again.

Two warning notes: Power OFF at the mains wall switch before interfering with the BUC and LNB coax cables. Leave the low voltage mutiway power connector between the power module and the modem plugged in at all times.

I don't think symptom above is related to dish pointing or polarisation. Check your BUC is actually connected. The centre pin of the F coax should stick out 1.5mm beyond the rim of the plug. Maybe your lat long coordinates are in error or maybe some other config entry is wrong.

Peak up the dish to best pointing ( 89 ) and the polarisation to 48 deg to 50 deg.

Peaking up means getting the pointing to the maximum digit value ( 89 in this case ). There is no 'good enough' value above which you can stop work. It is getting it to the exact centre that counts.

It is not easy. In elevation, winding the nut down to say 80 on each side and then halfing the count of the nut flats can get you to the middle, in elevation. In azimuth, move the two nuts apart by 2 turns and then repeatedly gently rest the dish each way in turn against the nuts till the same low value is seen on either side. Then wind both nuts in by same number of turns and flats.

The transmit beam is narrower then the receive beam so, in this instance while 83 might be a perfectly good receive quality, the narrow transmit beam may still be too far off.

Check that your lat long and config parameters are exactly as told. Then talk to Bentley Walker, check your lat long with them and and they can control your terminal from the hub end. They may ask you to make some commands etc and possibly adjust the polarisation by 1 or 2 degrees.

Best regards, Eric.

Feb 3^rd, 2009 at 7:07am

Thank you very much. I will do. It may be a result of jamming as well, as the probelms seems to have disappeared this morning

I will double check all cables today. I have been following the power down recommendations.

Feb 4^th, 2009 at 3:59pm

Hi,

it sounds like you are on the right track and the issue you are experiencing is more than likely cable/shorting issue. Please do not hesitate to contact us if you don't make any progress.

James - Bentley Walker.