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VSAT technology and installation >> Dish pointing and alignment >> IS -12 Signal Problem

Message started by techtest on Mar 24th, 2010 at 6:03am

Title: IS -12 Signal Problem
Post by techtest on Mar 24th, 2010 at 6:03am
Dear Sir ,

We have one link IS-12 link  in Ipricot S600 DVB  for downlink. This link is working fine from 6 months. Now in our ipricot we are losing signal and Eb no is becoming 0.0.

Now we have connected IPR-S 600 to spectrum analyzer and checked whether there is any interference or not. But due to our observation when the eb/no in IPR going to 0.0 but in our spectrum analyzer still the signal is showing. So we suspect IPR and changed the IPR then also same probelm is coming  in IPR Eb/no is becoming 0.0 but signal is showing in Spectrum Analyzer.

So Please help us to solve out the issue. HUB people is said everything is OK from their side .

Thanks a lot sir


Title: Re: IS -12 Signal Problem
Post by Eric Johnston on Mar 24th, 2010 at 8:26am
Some ideas:

Interference: Does the signal on the spectrum analayser really look exactly the same ? Are there any new humps along the top suggesting a carrier underneath ?  Are the gaps either side still exactly the same in width and depth ?  Is the (S+N)/N unchanged ?.  If (S+N)/N has gone up 3dB then you may have an identical carrier superimposed.  

LNB Frequency drift error:  Does the receiver have any frequency error display ?  Try widening the acquisition range or simply tuning the base frequency nearer to the daily average.  Does heating/cooling the LNB make any difference ? Try a PLL LNB in stead of DRO LNB.

Loose connection:  Does wiggling all of the cables make the fault occur ?

Use a 3 dB splitter and operate both receivers simultaneously.

What time and on what days does the fault occur / recover ?  Does anything else happen at this time ?

Does cycling the power to the LNB have any effect ? Turn the DC power off/on using receiver software. Leave for 5 minutes off to let it cool a bit.

Does cycling the power to the receiver have any effect ?

Does the fault occur instantly or is there gradual degradation at start and end of the outage ?

Best regards, Eric.

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