SatSig topic:

Idirect unlocking and relocking

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Apr 22^nd, 2009 at 2:31pm

Please I need forum's assistance. I have an Idirect 3100 series presently on AMC12 and for about 2months running now, it will occasionally unlock itself and start timing out for a maximum of about 40seconds to 1min and later re lock and acquire back into the network on its own. We spoke to our provider and they confirm from their end that they can see that we are losing signal packets but they could not offer any further assistance more than that. Please could anybody assist on what could be the cause(s)

Apr 22^nd, 2009 at 7:30pm

Two ideas:

1. The local oscillator frequency of your LNB drifts with temperature. Identify its model number and try to find its specification on the internet. Some DRO type LNBs can drift up to +/- 2 MHz. In your options file is the nominal receive frequency. Also there is a Rx-acquisition range. This allows the modem to sweep, looking for the wanted carrier, which it should find. Check your sweep range is wide enough for your type of LNB. If you reduce the sweep range and it makes the problem worse, or fails to lock at all then you have found the problem. Get the hub to send you an options file with wider rx acquisition sweep range. Somewhere in the modem status it may say what is the current rx frequency stress or offset. This will vary during the day but should not exceed the sweep range. Does anyone know of such a status parameter ?

2. Receive link marginal
Is the receive link quality low around the time of the outage? If so the problem could be rain at the hub site (affecting all sites), rain at your site, intermittent obstruction (vehicle etc), antenna mispointing (wind?).

Best regards, Eric.

Apr 23^rd, 2009 at 12:50pm

Agree with Erics thoughts above. Issue is probably LNB related but I would rule out weather attenuation at the uplink earthstation. I would also establish a telnet session to the iDirect unit and check a few things. Start with checking downstream SNR. Command from telnet: rx snr

You may be poorly pointed and it is compounding your ocassional rx unlock issue. I am thinking that you are probably LOW in downstream C/N already.