SatSig topic:

iDirect 3000 Modem Installation

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Jan 21^st, 2009 at 1:03pm

I am new to VSAT technologies. I am trying to get a lock on to W3A satellite. I have the following with me:

iDirect 3000 modem
1.2m Prodelin antenna
NJR2784HH LNB
2wat BUC

I have setup the equipment and ready to go.

Using iSite 7.1.1 am only getting between 2.1 and 3.000 volts when i do the pointing.
There is no obtruction on the installation site except for a bit of rain and cloudy.

Below is my location:
Latitude = -15.4186, Longitude = 28.2731
Lat = 15 degrees, 25.1 minutes South
Long = 28 degrees, 16.4 minutes East

Your suggestions are more than welcome.

Francis

Jan 21^st, 2009 at 1:11pm

What nominal polarisation (horizontal or vertical) has your hub told you to set for receiving ?

Has your modem been preconfigured or are you expected to configure it yourself using an options file ?

Best regards, Eric.

Jan 21^st, 2009 at 1:47pm

Hi Eric,

Thanks for the quick response.
The polarisation is vertical for receive and horizontal for transmission.
I am expected to configure the modem with the option file that they sent.
I am doing a test before i go on site.
Best regards,

Francis

Jan 21^st, 2009 at 3:30pm

This page will tell you the pointing angles: Dish pointing southern Africa, for example:

Polarisation:
Step 1: Start with the LNB sticking out sideways for true vertical polarisation. The broad faces of the LNB rectangular waveguide, which define the polarisation, will be on top and underneath.
Step 2: While facing towards the satellite, turn the feed/LNB/BUC assembly -53 deg anticlockwise.

Best regards, Eric.

Feb 4^th, 2009 at 9:40pm

Hi Eric,

Thanks for the input it was really helpful. We had to change the LNB for us to get a lock. The NOC also had to change the acquisition in the option file.

At this point i have two questrions:

1. Are there specific LNBs for each satellite or spacecraft?
2. Can you assist with interpretation of a sample option file?

I really need to understand these issues.

Best regards,

Francis

Feb 4^th, 2009 at 11:55pm

The NJR2784HH LNB is a DRO type LNB with a local oscillator frequency of 10 GHz and low stability +/- 900 kHz. It is suitable for 10.95-11.7 GHz satellite signals with large bandwidth and large bit rate and QPSK modulation.

Similar DRO LNBs
NJR types:
2754H with 11.3 GHz LO, 12.25-12.75 GHz
2744H with 10.75 GHz LO, 11.7-12.2 GHz

You need to choose an LNB which matches your satellite downlink carrier frequency and produces an L band output that in within the tuning range of the modem, e.g. 950-1450 MHz, 950-1700 MHz, 950-1950 MHz, 950-2050 MHz.

The choice of LNB will vary from one satellite to another and also on some satellites with many transponders you may need to use LNBs with different local oscillator frequencies.

You need to set the iDirect options file to sweep at least +/- 900kHz to find the carrier, for the low stability NJR LNB above.

LNBs with dual local oscillators are available with the alternative LO frequencies selected by 22 kHz tone on or off. e.g. Invacom SPV30SM LO=9.75 GHz or 10.6 GHz.

For narrow bandwidth SCPC carriers and those with advanced 8PSK and 16QAM modulation methods, Phase Lock Loop (PLL) type LNBs are recommended. These have much higher frequency stability and lower phase noise. Their reference is typically an internal crystal oscillator. External reference versions exist which need a 10 MHz reference from the modem. This can give the highest stability and accuracy as the modem may be temperature stabilised indoors or the reference derived from atomic GPS clock, for example.

Read more about how an LNB works.

Best regards, Eric.

Feb 5^th, 2009 at 9:21am

Hi Eric,

Many thanks for your input i really appreciate it.
Are you able to explain/interperate what is in the option file?
Please let me know if it is safe for me to post it here.

Best regards,

Francis

Feb 5^th, 2009 at 9:47am

For an explanation of the options file I suggest you contact your iDirect hub and ask about any parameter that concerns you.

I have no experience with iDirect and can only read the options file and guess what the various parameters are about. Many are obvious, but you need expert help to determine exact meaning and purpose. The values are software settings that help the modem to work and duplicate what is stored in the hub database. The hub normally sends you a complete option file to load with a new modem.

Regarding putting an options file here, I would read through your options file first and overwrite all passwords and IP address with xxxxxxxxxx. If you wish your location to be private reduce the accuracy of your lat long also. Rather than post a new options file why not refer to an existing one like forum thread: iDirect options file

Don't make any changes to your options file in the actual modem without approval of your hub !

We might be able to answer a few specific questions but please don't ask for a paragraph on each item.

Best regards, Eric.

Feb 5^th, 2009 at 10:10am

Hi Eric,

A million thanks for your assistance.
This makes my life with VSATs easier!

Thanks once more!

Francis

Feb 21^st, 2009 at 2:19pm

Hi all,

After getting a lock onto the satellite and iSite reading between 12 and 13 i have a few questions. I know we now have to mount the BUC:

1. What is the recommended signal strength reading?
2. What is the next step to have the VSAT commissioned?

Thanks,

Francis.

Mar 1^st, 2009 at 7:48pm

Quote:

Hi all,

After getting a lock onto the satellite and iSite reading between 12 and 13 i have a few questions. I know we now have to mount the BUC:

1. What is the recommended signal strength reading?
2. What is the next step to have the VSAT commissioned?

Thanks,

Francis.

12 to 13 is respectable for iSite pointing. Can you telnet into that idirect unit? Recommend checking your RX SNR by typing rx snr from a telnet session. Your C/N should be somewhere around 9-11 dB. (that value does have some dependency on your SLA and link budget).