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