Continueing with http://www.ruby-forum.com/topic/1983866,

I have planned to append a preamble before an actual signal and turn RX on
earlier than TX.

Then RX will receive a signal like below:

|---RX turn on------|---TX turn on-----------------------------
(---trash signal---)(---preamble---)(---actual signal---)

And this signal is demodulated and stored into a sink file.
After that, I run a program that extracts an actual data only and compare it
to the original.

My concern is that this preamble should be assumed to be perfect i.e. no
errors
Of course, there isn't no error. However if I set an amplitude to maximum
value, it can be said to be no error.
I have a pre-defined preamble sequence with length n (n = around 100-200,
can be changed)

Thus, I am trying to change amplitude of modulated signal for preamble and
actual signal
But I have problem with some quadrature modulation. Flow graphs are in
below:

http://dl.dropbox.com/u/11382666/for_gnuradio_mailinglist/M-DPSK.png
http://dl.dropbox.com/u/11382666/for_gnuradio_mailinglist/M-FSK.png

My question is that, how many samples after DPSK mod or frequency mod block
corresponds to each sample from file source?
I have to solve this problem in order to figure out how many samples are
generated from preamble with length n.
If I know that information, I can set a duration for Multiply const block
having large value for preamble and normal value for actual signal

And second question is that, although I know that information, I don't know
how I can control value.
For example, preamble with length 200, then I want to set large value for
duration 200 * x (number of samples generated after DPSK, Frequency mod),
and after that I want to set normal value for remaining duration.

Is it too complex for gnuradio-companion flow graph to make? And is python
hard coding possible?

-- 
Seokseong Jeon (aka Songsong Gee)
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