Debugging osmo-trx constellation on XTRX SDR

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Alexander Chemeris alexander.chemeris at gmail.com
Thu Dec 22 14:37:22 UTC 2016


Hi Thomas,

We're porting osmo-trx to our XTRX and we see some weird
constellation (https://goo.gl/photos/1KycUsv26Z6T6aN97). It looks like
a normal GMSK circle is there, but there is also a square like if a
signal is clipped. Do you have any idea what could cause this from
your previous experience?

We're running osmo-trx at 4 SPS. Then we double sample rate in
software (XTRX can't handle sample rates below 2 MSPS yet) and then
transmit. See first image above.

Then we tried to increase sample rate and enabled 4x interpolation in
LMS7 - that led to a distorted cicrle + square constellation
(https://goo.gl/photos/zMZRecxmZsqiCYMHA).

-- 
Regards,
Alexander Chemeris.
CEO, Fairwaves, Inc.
https://fairwaves.co



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