Hi Anish - I would argue the flowgraph is a potentially a model
for a broken audio device :).
That is, the input signal to the WBFM block is not a 48 kHz signal -
it's a null source, but you're telling the WBFM block to expect an
input frequency of 48 kHz.
If you were to add a signal source of 48 kHz, you would need to add
a rational sampler in front of the WBFM block for a quadrature rate
of 480 kHz.
And the typical bandwidth for a WBFM signal is roughly 200 kHz.
A mismatch in sampling rates in a flowgraph is a common problem.
And there are other resamplers.
What I did previously was kludge so I could see the sine wave better
without any hardware. If the other devices are actually using a null
source, then they must be clipping the side bands.
-- Cinaed
On 5/15/21 5:34 AM, Anish Mangal wrote:
Hi. I performed some more tests and report the results on
this thread.
I'd love some advice with which I can produce a simple FM
modulated sinewave with gnuradio and limesdr. If someone on
this mailing list has a limesdr, and some bandwidth to test
this out, I'll be more than happy to provide my flowgraphs.
Thanks!
So far as I am able to tell with my limited knowledge
of limesdr and gnuradio, it seems like some kind of issue
with the right settings to me.
The gr-limesdr provides a sink block that allows one to
use an .ini file instead of the settings done via the
block's settings. I will have access to the radio in a few
days' time and am thinking i'll copy over the .ini file
that was used in sdrangel and use the exact same one in
gnuradio and see what happens.
Hi Anish - yes, I removed the
LImeSDR block from the flow graph.
I inserted a throttle instead since I didn't have any
front end hardware available at the time.
I do have a WBFM receiver using gnuradio running on a
HackRF which works great.
But I'm using low pass filter taps in the complex
rational resampler which leads the WBFM receiver.
-- CInaed
On 3/20/21 7:52 PM, Anish Mangal wrote:
Hi Cinaed,
But this is without the actual LimeSDR sink
block? Or with it?
Because, I can produce a clean sinewave with a
HackRF, but not the LimeSDR.
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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