Here is an attempt to give you what you requested. It appears to
me that the fundamental peak is +/- 12 kHz which seems very wide
to me. Also included is a copy of the flow graph.
Hey Fred,
nice to have you around!
Could you maybe post a screenshot of the frequency plot so that
we can evaluate what you mean with "huge"?
I think you might not be realizing that DSP like GNU Radio does
it doesn't care about the number you set as sampling rate – i.e.
a GMSK symbol in the configuration you're using of the GMSK mod
will always be 2 samples long. And that is what defines the
shape in the spectrum. So, the frequency axis in your frequency
plot is really just -bandwidth;+bandwidth _labeled_.
Best regards,
Marcus
On 04/20/2017 07:19 PM, Fred Castello
wrote:
Hi there,
My goal here is to ultimately develop a telemetry system but I
am starting very simply by building a GMSK encoder using a file
sync fed directly to a decoder. It seems to be working as I can
see the constellation diagram (which eventually goes away-dont
know why) and on the scope sync I can see the phase transitions
but in the FFT sync it appears that the bandwidth is huge. From
what I understand, I would not want to filter the results going
from the modulator to the demodulator, but I may not understand
that correctly. I know I have a long way to go, but I am just
trying to learn as I go and try to figure out the theory and see
how it applies as I build using GNU radio. Thank you anyone for
your help!! I am including the Flow Graph as well as the test
file that I am using for the file sync. Much appreciated.
Fred
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