trying to play two radio stations simultaneously

[Chris Gorman]

Hello All,

I'm trying out jean-michel.friedt's course on digital communications
and have a problem with getting two radio stations to play
simultaneously.  I have tried to follow jean-michel's example, but am
getting caught somewhere.  I get one radio station and hiss on the
other.

I've tried a few combinations, but haven't got a logical successful
solution.  I am choosing two local radio stations and can tune them
independently.  The first radio station is the osmocom source ch0
frequency.  This station I can tune without trouble.  The second
station is determined by s frequency translating filter and I make the
center frequency a negative difference between the ch0 frequency and
it's nearest neighbour.  In this case I'm choosing ch0 frequency
90.7e6 and center frequency -800e3.  (For a radio station at 91.5
MHz.)  Somewhere here I am getting into trouble.  This station can be
heard but is mostly hiss.

I'm including my grc file and a screenshot of my flow graph with the
hope that someone can point me to my error.  Thanks in advance.

Chris

fdma2.pdf
Description: Adobe PDF document

fdma2.grc
Description: application/gnuradio-grc