constellation diagrams?

S

steptoe

Member
My Satellite Setup
astra 19.2
astra 28.5
hotbird 13
My Location
luton
Hi
Constellation Diagrams
just interested in anyone who uses this on their meters just curious if they are hard to interpret as i only understand tight dots means good loose and fuzzy bad.
Is there more to them as a diagnostic tool or do all the BER/MER readings etc cover this.
S:confused:
 
Hi,

Just take a look at the document linked in the first thread of this sub-forum!

The constellation diagram allows you to understand if the bad reception is due to i.e. bad alignment or rather a fault in the signal itself, i.e. as a result of a faulty cable or LNB.

This comes specially handy when aligning a dish for DVB-S2 reception: due to reduced bit error correction, you may have a good signal level, yet the signal is not demodulated correctly. This can happen when the LNB is not propperly tilted.

The constellation diagram is indeed a good graph to quickly understand what the signal looks like. You need to understand that each segment represents the demodulation of that bit. If points are clearly in the center of each segment, the tuner will be able to demodulate the signal. If dots spread out too much, they may be interpreted as the wrong bit.

Cheers,
vma
 
vma said:
Just take a look at the document linked in the first thread of this sub-forum!
Click to expand...
Hi,

Can you please give a link to that thread ? The tread must have moved. :)

I'd love to learn more about Constellation Screen, and as you mention specifically understand what in the constellation shows (how the dots on the screen should or should not be):
a) bad alignment of the dish or
b) cable or LNB fault

Thank you!
 
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