Re: [Discuss-gnuradio] simple mod-demod combinations doesn't work

[Sylvain Munaut]

Hi,

> Maybe I am wrong, but i expect an
> lossless connection in GRC if I directly connect an modulator to its
> appropriate demodulator - particularly when i use the default values.

Yes you are wrong.

Demodulation is not an exact process and the various loops in there
will take some time to lock and so the beginning will be corrupted and
your output won't be synced on the bytes boundaries of your input.

Before modulation you need some kind of pre-processing to add
synchronization patterns and stuff like that and eventually some
padding data both at the beginning and the end to let the loop lock
and let stuff flush at the end if you want the full data to be
recovered, then you need to detect, align and remove all of that at
the output.

Cheers,

    Sylvain