[Discuss-gnuradio] BER in bert- example

[Mattias Kjellsson]

Hi list,

There is a function called 'ber' in receive_path.py in the python bert 
example.

def ber(self):
       return (1.0-self._ber.density())/3.0

From where does the 3 originate? Some lines above, there is this comment:
# Descramble BERT sequence.  A channel error will create 3 incorrect bits
self._descrambler = gr.descrambler_bb(0x8A, 0x7F, 7) # CCSDS 7-bit 
descrambler

But from my tests I see that
1 bit error in -> 7 bit errors out
2 consecutive bit errors in -> 2 errors in the output
3 consecutive bit errors in -> 7 errors in the output
4 consecutive bit errors in -> 4 errors in the output
...
And so forth up to 7 (Length of the lfsr)

The reason I ask is that if I want to change the scrambler and/or the 
modulation, I assume that this "magic number" will change as well.

BR
//Mattias