Hi Anish - I think I may have found the problem.
When the complex rational resampler is on the out put of the WBFM,
it bothered me later that I couldn't see the top of the signal.
The scale on QT GUI SINK was clipping the signal but not the
computational noise.
In the QT GUI SINK, if I set the Y-min to be -99 and Y-max to be 0,
the signal looks perfect.
And if the receiving RTL dongle has noise while listening, it may be
a DC offset problem.
-- Cinaed
On 3/18/21 6:58 AM, Anish Mangal wrote:
Here are two debug logs from LimeSuite GUI. In one, I load
the settings that gnuradio does to the limesdr and see the
debug log. The other is the settings file which the sdrangel
writes.
If I diff them, among other differences, this is what I see
in the end of the sdrangel-debug-log
DEBUG: Selected: VCOL
DEBUG: csw 169; interval [166, 172]
DEBUG: M=195, N=3, Fvco=1300.000 MHz
And this is what I see in the gnuradio-debug-log
DEBUG: Selected: VCOM
DEBUG: csw 174; interval [171, 177]
Now, I'm *very* new to this.. but could it mean that
different VCOs are used in both cases, and in the case of
gnuradio, it maybe has some issues to stabilize to some freq?
Hi all
There is something wrong in this simulation.
Attached is a flowgraph with a selectable Lime SDR
Source, and a RTL-SDR dongle as receiver. I tested this
with a Lime SDR Mini.
- I was suspecting a Lime SDR issue, however this is not
so clear.
- As Anish I also tested a const source.
- The flowgraph is running fluently and I dont' see any
error message about transmission to Lime SDR
Conclusion of my simulations :
- with a const source (=1) at Lime input : everything is
OK, the received signal is frequency shifted (normal)
and the SNR is correct if LimeSDR Gain is sufficient
- Using ratioanal resampler followed by WBFM Transmit
Same reslt, everything is OK
- First source+ WBFM + Rational resampler (this is a
sample file found on LimeSDR website
- the spectrum is not correct (look like a modulated
signal
- the received signal magnitude is not constant
- BUT the send signal on the Time Sink look like
correct. ( I.E =1+j0 as for others sources, whitout
any glicht)
How can we further investigate this?
On 18/03/2021 13:13, Anish Mangal wrote:
And, if I try the attach gnuradio file,
which is just a constant source of value '1' going to
the limesdr sink block, I actually see a sine-ish wave
without the glitchy behavior.
I tried your grc and got the same result.
See the waveform's envelope in this
oscilloscope capture. Note the timebase.
This isn't happening in SDRAngel.
I moved the rational
resampler block from the output side to the
input side of the WBFM.
The output of WBFM block needs to match the
input of your LimeSDR.
I don't have the LimeSDR software installed so I
couldn't look inside the sink block.
-- Cinaed
P.S - yes, you can post GRC's on the mailing
list - they're text based.
On 3/17/21 4:14 AM, Anish Mangal wrote:
I linked
the grc file in the original email.
Attaching it here as well. (Don't know if
the mailing list allows attachments)
Hi Anish - since this is a gnuradio
mailing list, the starting point would
be to post your GRC - which is an yaml
or text file.
-- Cinaed
On 3/16/21 11:19 PM, Anish Mangal
wrote:
Hi! Any pointers to where I can
start debugging this?
Maybe run gnuradio-companion in
debug mode?
Do more simpler tests?
Any other suggestions?
I have a HackRF One and will
try the exact same comparison
there too ... SDRAngel & grc
Hi,
To properly explain the
issue I'm facing, I recorded a
video showing Oscilloscope
waveforms.
The gnuradio flowgraph is
here:
The various versions of the
software/hardware involved are
the following.
gnuradio-companion: 3.8.2.0
(Python 3.6.9)
gr-limesdr: branch gr-3.8
(last commit
47511dd58de1695b70e1028366411bada85eb60f)
sdrangel: 4.12.1
OS: Linux Mint 19.1
CPU: Intel© Core™ i7-4900MQ
CPU @ 2.80GHz × 4
RAM: 16GB
H/w: Thinkpad T440p
tl;dr
I'm trying a simple test to
create a sinewave output from
a WFM modulator block. If
there is no audio input, its
WFM modulated signal should be
a simple sinewave. If I test
this with SDRAngel, I see a
clean-ish actual sinewave in
time domain on the
oscilloscope. But if I try to
do the same with gnuradio, it
seems to produce a glitchy
signal.
Could I have any advice on
what I might be doing wrong?
Thanks,
Anish // VU2TVE
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