On 03/23/2016 03:14 PM, Tom Golden wrote:
Here's my flow-graph along with a snapshot of the constellation and FFT.
Thanks!!
-Tom
What output level is the RF modem producing? Are you using attenuators
between it and the RF input of the USRP?
I note that you have the RF gain on your capture set to 0.
Also, I don't recall whether the polyphase resampler requires that the
input already be Nyquist-limited before it gets resampled.
I know some of the other resamplers do that, otherwise, you get
aliases in your output passband.
Since you're looking at a 9600BPS signal, you should probably have
sampled this at 250ksps--the lowest rate possible with the N210--
that makes filtering later less computationally intensive.
On Wed, Mar 23, 2016 at 1:01 PM, Marcus D. Leech <mle...@ripnet.com
<mailto:mle...@ripnet.com>> wrote:
On 03/23/2016 02:48 PM, Tom Golden wrote:
Hi,
I'm a novice gnu radio user. I'm using gnuradio with an Ettus
N210 cabled to a modem transmitting GMSK 9600bps. This is
just for a test to verify the modem transmit bits.
I'm having issues with resampling. The N210 clock can't be
set to a multiple of 9600, so I'm attempting to resample. I've
tried various mechanisms but the output after resampling to
96000 is too noisy to successfully decode bits. I've tried
the GMSK demod block as well as the combination of Quadrature
Demod->Clock Recovery MM->Binary Slicer - and neither works.
I've also played with the Polyphase clock sync but I don't see
any noticeable difference. Can anyone recommend a solution?
Thanks!!
-Tom
For a first step, it would be useful for you to share your
flow-graph with the list.
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