SatSig topic:

Pointing Issues in Iraq and the HX50

(Read 5493 times)

Dec 13^th, 2009 at 9:30am

Hello All,

I've read the forum to make sure my problem was not covered already. There were several pointing tips that helped us out (the angle tool for instance), but I think our issue is a little deeper than dish aiming.

We are in Iraq, our provider is IPDish, we are using an HX50 modem and we are pointing at 95E (NSS 6).

Our service provider has tried to help us, but they are telling us right now it is a dish pointing issue. No matter where we point our dish we get nothing higher than a 29 signal strength. We have swapped out cables and tested the DC output of each connection....aimed, re aimed and re-re-aimed the dish several times but nothing is showing up to indicate we are on the right path.

Our configuration info for the site is as follows as per our NOC:

Longitude: 95 East
Frequency: 19220
Symbol Rate: 2000000
LNB 22KHz Switch: On
DVB Mode: DVB-S2-ACM
Frequency Band: Ku Band - QPSK
Recieve Polirization: Vertical
Transmit Polirization: Horizontal

Recieve LNB Type: TG_1024572-0001
2 Watt

We are using a makeshift stand out here, and our LNB is a 1024572-0001 REV A (NJR2184HH) which you turn in its sleeve to achieve polirization.

According to our location we are aiming at 110deg magnetic, with an elevation of 22.6 deg and a polirization of -48.6. When facing the dish that puts the LNB somewhere around the 5 oclock position.

If the parameters for our modem are correct and we are pointing the dish correctly we should at least see a signal spike to indicate we are heading in the right direction....obviously the common frustration with first timers here.

Any advice would be appreciated.

Dec 13^th, 2009 at 11:03am

I'm less familiar with the Mid-East coverage, but two things in your post caught my eye. That Frequency: 19220 doesn't look right to me, might bear confirmation. And the "makeshift stand" description is concerning. It appears you have your Az/El/Pol settings in the ballpark, but they're predicated on a mount/mast/pole/stand that is plumb. That is, completely vertical in all directions. If you don't start out with a proper mount, the Az/El/Pol angles you set into the equipment could be pointing anywhere. A signal indication of 29 pretty much represents plain old noise. Whereas you may have the correct El angle set into the dish, you're likely scanning for your signal either above or below the actual satellite band. But confirm that frequency too

//greg//

Dec 13^th, 2009 at 11:19am

Signal readings
The signal reading scale works in two parts 0 - 29 and 30 - 100.

The range 0 - 29 measures power and you will get such readings on any signal source, i.e. all satellites and even the sun. Powerful satellites will max out at 29.

Only if the modem configuration settings match the received carrier will the scale jump into the range 30 - 100. Typical value 92. Peak up.

If you have maxed out at 29 you are on the wrong satellite or wrong polarisation or wrong type LNB or have the wrong configuration settings.

Tuning
Your NJR2184 LNB has a fixed local oscillator frequency of 10000 MHz and is intended for reception 10950 - 11700 MHz with frequencies into the cable of 950 - 1700 MHz.
Since the LNB has just one local oscillator frequency your 22kHz tone is not needed and should be OFF.
The NJR2184 is a cheap DRO LNB with frequency error up to +/- 500kHz. For use with a small 2 Msps outlink carrier, and particularly HX system with higher order modulation, a PLL type LNB (Invacom or similar) would be preferred.

Check with your service provider:
What is the downlink carrier frequency from the satellite ? e.g. 11.123456 GHz
What is the local oscillator frequency of your LNB supposed to be ? e.g. 10 GHz
What is the carrier frequency in the cable to the modem ? e.g 1123.456 MHz
What is the carrier tuning setting for the modem (in units of 100kHz) e.g. 11235 (in units of 100kHz)

As Greg indicates above there is concern about your tuning setting of 19220 (units of 100kHz). This is beyond the design range of your LNB.

Polarisation
You say "polirization of -48.6. When facing the dish that puts the LNB somewhere around the 5 oclock position."

For vertical receive polarisation you must start with the LNB arm sticking out sideways (either side will do).
To apply a -48.6 deg adjustment you need to turn the whole feed assembly (feed horn/OMT/filter/LNB/BUC) anticlockwise by that amount, while facing towards the satellite in the sky. The end position will be approx 1:30 or 7:30 on a clockface, as viewed facing towards the satellite in the sky. Set the angle accurately to +/- 1 deg.

Your 5 o'clock position, while facing backwards towards the dish makes sense and is OK.

Best regards, Eric.

Dec 13^th, 2009 at 11:57am

We contacted the NOC after reading this forum to ask if the LNB was able to support the frequencies we were inputting. Of course we got back an affirmative reply, which is why the LNB Type is set as it is.

As for the stand, by makeshift I mean it is weather worn. Rusty screws and the like that need a lot of attention to stay put. We have checked to ensure the stand rests level, but there is going to be a fudge in the numbers with Az and El as we fine tune it.

I will ask the provider the questions you hinted at Eric, see what they send us back.

Thanks for the quick reply,

Josh

Dec 13^th, 2009 at 1:35pm

Hot off the presses from my NOC rep:

What is the downlink carrier frequency from the satellite ?- 11.672GHz
What is the local oscillator frequency of my LNB supposed to be? 10/9.75Ghz
What is the carrier frequency in the cable to the modem ? 1.922GHz
What is the carrier tuning setting for the modem? 1.922GHz

Dec 13^th, 2009 at 2:35pm

That information does not make sense.

I am not aware of any LNBs that have 10/9.75 GHz switchable LO frequency. Typical switchable LNBs have 9.75/10.6 GHz or 10/11.3 GHz options. A 22kHz tone (or in some cases +18 volts) selects the higher frequency of the pair.

My guesses are:

11672 - 9750 = 1922 MHz, or 19220 into the modem tuning.
For the above to work you would need a new LNB with local oscillator of 9.75 GHz. (Also necessary to verify that the new LNB will work up as far as 11672 MHz and that the modem will work as high as 1922 MHz)

11672 - 10000 = 1672 MHz, or 16720 into the modem tuning.
This should work with the LNB that your have now, LO=10GHz
Tune the modem to 16720 (units of 100kHz)

Once you have it working, please tell your service provider so they get it right for the next customer. They also need to correct their database so that your modem software does not get "upgraded" and downloaded with a bad configuration and stops working.

Question to Greg and anyone else.. What it the upper end of the receive input tuning range for an HX modem ?.

Best regards, Eric.

Dec 13^th, 2009 at 6:28pm

No reason to suspect OP is reporting incorrect LNB model number. So based upon known 10GHz LOF, and newly reported downlink RF frequency 11.672 GHz, I agree with modem Frequency 16720.

Hughes didn't publish the IF range in the HX50 tech sheet. But it is listed as Ka-band capable. To me, that means 900MHz-2250MHz

//greg//

Dec 14^th, 2009 at 2:28pm

Only the HX150 has a receive frequency range specified 950 - 2150 MHz. The HX150 model is also the first, I believe, of the Hughes range of modems to have a normal RF interface, on both transmit and receive, so that it works in conjunction with standard LNBs and BUCs.

see
Hughes HX50 modem remote terminal specification (86k pdf file)
Hughes HX100 modem remote terminal specification (93k pdf file)
Hughes HX150 modem remote terminal specification (87k pdf file)

Best regards, Eric.

Dec 14^th, 2009 at 3:05pm

Not to put too fine a point on it Eric, but neither the HX50 nor HX100 spec sheet even mentions IF output. But you know they both have one. Then note that all three are Ka-capable. By extension, the 950-2150 MHz spec listed on the HX150 sheet is applicable to all three.

But don't expect the higher end to be available for C- or Ku-connections. It's capable of over 1450MHz, yes. But won't output it unless/until the modem is set up with Ka-band satellite parameters. And even then, I believe those higher IF frequencies are for the transmit IFL only.

//greg//