[mythtv] Ticket #1049: DVBSignalMonitor needs to be able to monitor NIT/SDT

[Allan Stirling]

Daniel Kristjansson wrote:
> On Tue, 2006-06-06 at 23:55 -0400, Yeasah Pell wrote:
>> Actually, many cards do much more than a little PLL, and there's a good 
>> reason -- LOF error on LNBs can be significant (easily greater than your 
>> tp spacing -- remember, it's some consumer quality ~10GHz oscillator 
>> powered by some dodgy PCI card's power supply connected by a long piece 
>> of coax in conditions which are alternately hot and cold, dry and wet), 
>> so a zigzag frequency walk sometimes needs to happen.
> 
> I doubt this is as much of a problem as the DVB devs seem to think.
> I actually asked Kenneth Aafloy to chart the LNB drift and get back
> to me, he never did. My EE background is in radio engineering, the
> job of the downconverter portion of the LNB is just to frequency
...

I had a spare tuner, so here you go:

    1512 1626758
   37259 1626760
   25694 1626761
   25447 1626762
   38885 1626764
   35415 1626765
   27499 1626766
   21704 1626768
   27229 1626769
   56037 1626770
   60944 1626772
   56929 1626773
   76290 1626774
  123514 1626776
   65243 1626777
   29411 1626778
   10385 1626780
    1500 1626781
    1012 1626782
     467 1626784
    1074 1626785
    9970 1626786
   11928 1626788
    5861 1626789
    7590 1626790
    9835 1626792
    6568 1626793
    4568 1626794
    5767 1626796
   13629 1626797
   18169 1626798
   17516 1626800
    6536 1626801
     149 1626803

This is generated with a modified femon which polls the card 
  about 5 times a second.

First column is the number of "counts" -  Second column is 
the DVB real tuned frequency, as reported by the card.

This is tuned to the "Sky One" transponder on Astra 28.2, so 
it 'should' be centered at 12.285GHz - 10.6Ghz (LOF) =1.685Ghz

Interestingly, there are periodic variations, but it doesn't 
appear to be only temperature related.

Total swing for this test is 45kHz (0.003%) which is 
probably not significant. Obviously, longer cable runs, 
worse power supplies, cheaper LNBs may give worse figures.

Cheers,

Allan.