SatSig topic:

iDirect iSCPC frequencies config ?

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May 24^th, 2011 at 12:57pm

Hello,

My knowlegdge on this technology is close to zero, but we need to setup a connection for a TV broadcaster using iSCPC technology. We have received list of frequencies and bandwiths from a satellite operator (Telenor on IS 10-02) and my question is - which frequency goes where in the iSite setup, respectively for TX and RX sites?

Thank you very much!

May 24^th, 2011 at 5:21pm

I've put the image of your frequency assignment table above.

I suggest:
512k carrier: FEC=0.66 Symbol rate = 387.88 Modulation = QPSK
2591k carrier: FEC=0.66 Symbol rate= 1962.88 Modulation = QPSK

These two carriers would just about fit into 3 MHz total bandwidth.

Talk to the Telenor hub about this and see if they can do any better. The possible choices of FEC ratios and modulation types depends on the equipment they and you have.

Your receive tuning frequency into the modem will depend on the LNB you are using. If you have an LNB such as NJR2837S it will have a local oscillator at 10 GHz so the frequency of the 2591 kbit/s carrier into the modem will be 11538.856 - 10000 = 1538.856 MHz.

I hope someone with iSCPC experience will answer this question below - and correct any of my misunderstanding, as I know little about iDirect.

Best regards, Eric.

May 26^th, 2011 at 9:23pm

Thank you Eric!

My question was more frequencies wise. Our software version does not allow us to specify FEC, Symbol rate and Modulation anyway. My question is probably very dumb, but I have to ask it. When one looks in the iSite soft must specify RX and TX frequencies. We substract the LNB frequencies, so no worries.

But my question is which ones of the frequencies on the picture from "Special instructions" goes where on remote point and on base point iSite setups? Or we have to use frequencies from upper row only (U/L and D/L frequencies)?

Thank you.

May 26^th, 2011 at 10:33pm

Regarding the carriers, I am assuming that the large carrier is from the hub to the remote site:

512kbit/s: uplink from remote site = 14337.375 MHz downlink to hub = 11537.375 MHz
Assuming your remote site uses a BUC block up converter with a local oscillator of 13050 MHz. This is typical but you should check.
The transmit tuning of the remote site modem will be 14337.375 - 13050 = 1287.375 MHz.
At the teleport hub assuming a 10 GHz LO LNB the hub tuning will be 11537.375 - 10000 = 1537.375 MHz

2591 kbit/s: uplink from hub site = 14338.856 MHz downlink to remote = 11538.856 MHz
Assuming your hub site uses a BUC block up converter with a local oscillator of 13050 MHz. This is typical but you should check.
The transmit tuning of the hub site modem will be 14338.856 - 13050 = 1288.856 MHz.
At the remote site, assuming a 10 GHz LO LNB the remote modem tuning will be 11538.856 - 10000 = 1538.856 MHz

Get your hub to check all the calculations.

The hub must tell you how to tune your remote receive modem with frequency, symbol rate and FEC options. Once you are receiving successfully from the hub, the hub may be able to control your modem remotely and set your transmit configuration by remote command.

Before transmitting from the remote site speak to the hub. You will first need to correctly receive the outlink signal from the hub. Then ask their permission to transmit. Transmit a very low power CW carrier initially and wait till they see you are at the correct frequency and adjust your polarisation. they will then allow you to increase power to nominal under their verbal instruction. If you lose the phone call turn your transmit off.

Best regards, Eric.

May 27^th, 2011 at 8:39am

Thank you Eric, this one was helpful!

In fact remote and hub are operated by us - it is a SNG system (satellite news gathering) used by a TV operator. The satellite operator just "teleports" the data.

Does this changes the situation?

Thank you.

May 27^th, 2011 at 10:51am

Make sure before the first transmission by either site, that the antenna is pointed at the correct satellite.

Talk to the satellite operator NOC to verify your first transmission of low level CW carrier and get your polarisation lined up perfectly with their verbal help.

Despite what you say, you do need to know what modulation and FEC ratio you are using as this affects the bandwidth of your carriers, that must fit within your purchased 3 MHz bandwidth. If you are too wide you will interfere with adjacent transmissions. Talk to iDirect and get instruction manuals for the operation of your iSCPC modems at each end.

Get someone to help with power level setting of your transmit carriers. Correct eirp levels will be specified by the satellite NOC and the actual modem power setting will need to take account of your dish sizes and cable lengths. You must not overdrive the BUCs or cause interference at the satellite by using wrong levels.

Always ask the satellite NOC's permission before bring up the remote site and get their help with polarisation alignment if your own hub does not have competent operator with spectrum analyser.

It is critical that your transmissions do not cause interference to other services on the same or nearby satellites.

You say that the application is SNG. Clarify which direction is the larger bandwidth carrier and make sure all the documentation agrees wth this. My assumption that the large bandwidth carrier is from the hub to the remote may be wrong.

Note that if you are using a small dish to transmit a 2591 kbit/s carrier then the BUC power (watts) will be seriously dangerous. Do not get your head or body parts between the feed and dish or in the beam to the satellite. It will fry your eye lens in seconds.

Best regards, Eric.