Preamble and simple framer and correlator

Continueing with How to synchronize RX with TX? - GNU Radio - Ruby-Forum, and
Appending preamble with different power - GNU Radio - Ruby-Forum

I am trying to append preamble to a signal so that RX can recognize it
see a start position of data exactly.
I roughly draw what I thought.
[image: desired_signal.jpg]

I learned that there is gr_simple_framer and gr_simple_correlator in
I guess that gr_simple_framer appends sync field and other files, and
gr_simple_correlator removes additional fields by gr_simple_framer

To verify this guess, I make a flow graph and run it.
[image: framer_correlator_test.png]

As a flow graph runs, file size of framer_sink goes large, but that of
correlator_sink remains 0 forever.

I have tried to figure out how I can use these blocks from doxygen (
GNU Radio Manual and C++ API Reference: Main Page)
But I cannot figure out it easily.
Does anyone know what value should be in Payload Byte Size for framer
and where I can find some examples of these two blocks?

On Fri, Jun 24, 2011 at 2:49 AM, Songsong G.
[email protected]wrote:

Seokseong Jeon (aka Songsong G.)

Look at the digital examples in
gnuradio-examples/python/digital/ They are a bit
to follow when you first look at them, but you’ll find a lot of the
stuff in gnuradio-core/src/python/gnuradio/ and (same path)/blks2impl
includeing,, and the modulators/demodulators
(dbpsk[2].py, dqpsk[2].py,, etc.). The receiver chain that uses
of these pieces uses a preamble to detect the packet and do the
They should help you understand the blocks you are interested in.