---------- Forwarded message ----------
From:
Songsong Gee <address@hidden>
Date: 2011/4/1
Subject: Re: [Discuss-gnuradio] DPSK mod/demod block work well?
To: Tom Rondeau <
address@hidden>
I have an additional problem
It did not change much.
And here are scope plots
Everything is fine, but at the beginning,
There are ""3"" points which are not in the source.
Does DPSK demod block add some extra information?
Currently, I solved this problem just adding Skip 3 Head block.
However, if I change DPSK to DQPSK? or D8PSK?
I think that this value ""3"" might be also changed.
This extra 3 bits are inevitable?
2011/3/31 Songsong Gee
<address@hidden>
Thank you for your answer
It was a simple problem!
But I couldn't think of that :)
Thanks
2011/3/31 Tom Rondeau
<address@hidden>
On Thu, Mar 31, 2011 at 9:07 AM, Songsong Gee
<address@hidden> wrote:
I just made very simple dpsk mod/demod testing flow graph
I didn't change any parameters in mod/demod blocks.
How can I get a good signal after mod/demodulation?
Well, the secret is that you really are getting good signals out of the demodulator, it's just not in the form that you think it should be.
The modulator takes in packed bits; that is, characters between 0 and 255. You are only giving it 0's and 1's. The output of the demodulator is providing you with unpacked bits, so each character represents a single bit. You will want to put an unpacked_to_packed block after the demod to put them in the same format as your input.
The reason why you are getting the zeros at the output is because a '1' in the input is really a '00000001' and a '0' is really '00000000', which is what you see in your sink.
Tom
--
Seokseong Jeon (aka Songsong Gee)