BBC HD switched to 8PSK,so from now on most of the broadcasts in 1920??

steffan_st

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8PSK is claimed to be more efficient than QPSK,so will there be more 1920 content in stead of 1440?

For the UK licence fee payers i think 1440 is rather crappy.For example,if you watch some episode of a nature program on BBC and the following week you watch the same episode on German ZDF,the ZDF pic quality is by far superior to BBC:s.Or used to be maybe I should say.
 

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The switch to 8PSK FEC 2/3 adds 4.5 Mbit/s netto datarate because of the more efficient modulation. So now 44.7 Mbit/s are available.
This was done to gain capacity for the new BBC 1 variations for Scotland, Wales, Northern Island. It has nothing to do with the picture resolution.

There will be 5 HD channels in the end - BBC 1 HD (England,Scotland,Wales,Northern Ireland) and BBC HD.
so about 8.9 Mbit/s per channel on average (minus sound, structural data).
 

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How is reception now that it is 8PSK?
 

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No real difference.... QPSK 8/9 needs a C/N of 6.2dB, 8PSK 2/3 needs 6.62 dB.
 

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my sky box shows improvement since the change: around 8-9pm, when reception starts to get poorer, before the quality meter (judging by the line) showed 40%, now it's 50%. i know sky boxes are not accurate for signal measuring, but the line is definitely higher.

/budapest, hungary - 150 gibertini/
 

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bbc hd now,,,,, sig 83% qual 100% central southern norway hummy 2000hd 120 motorised dish maximum 0.3 quad lnb
 

steffan_st

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timo_w2s said:
How is reception now that it is 8PSK?

Just slightly better in the south east of Sweden.
 

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Interesting, thanks.
 

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Btw the datarates of the channels haven't changed - they fill up the additional capacity with null bytes.
 

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a third FTA HD Stream has appeared mapped to SID 6943. Currently showing a still picture.
 

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BlindFaith

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You'll find some figures in ETSI EN 302 307, par. 6 Error performance.
In general you can always apply Shannon's law about the channel capacity ;)
A higher rate (on the same channel, same channel coding) riquires a higher signal/noise ratio.
 

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In general you can always apply Shannon's law
Not that simple because you need to know the correction factor. DVB-S and DVB-S2 have different correction factors so it is not possible to do a side by side data rate comparison.
 

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very simple in this case.. ..both use dvb-s2 ;)
 

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very simple in this case.. ..both use dvb-s2 ;)
Still doesn't help us convert to C/N in dB. Someone said 6.6dB above but there is absolutely no way to maintain lock for this transponder at that level.
 

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DVB-S2: 8PSK | QPSK
1/4 : |-2,35dB
1/3 : |-1,24dB
2/5 : |-0,3 dB
1/2 : | 1,0 dB
3/5 : 5,5 dB | 2,23dB
2/3 : 6,62dB | 3,1 dB
3/4 : 7,91dB | 4,03dB
5/6 : 9,35dB | 5,18dB
8/9 : 10,69dB | 6,2 dB
9/10: 10,98dB | 6,42dB


DVB-S: QPSK

1/2: 2,69dB
2/3: 4,36dB
3/4: 5,46dB
5/6: 6,53dB
7/8: 7,24dB
Info is from a Tandberg manual.
C / N0 ratio for failure.
The values are good to compare the various modes, not so easy to use to compare to what a box displays as an absolute number.
 
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