Re: [Discuss-gnuradio] dB or dBm

[GNUBeginner]

I am already aware of what the maximum allowable receiver power which is -5
dBm. That is why I am starting from 0 dBm with 20 dB attenuator before
injecting it to the HackRF One.



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Re: [Discuss-gnuradio] dB or dBm

[lists]

You can get a soft failure by overloading a receiver input, let alone a hard 
failure. If you are testing a $15 dongle, no big loss. If you are testing a 
real receiver, I would check to see what is the maximum allowable input power. 

Using a signal generator is a matter of RTFMing.

  Original Message  
From: GNUBeginner
Sent: Wednesday, June 21, 2017 11:57 AM
To: Discuss-gnuradio@gnu.org
Subject: Re: [Discuss-gnuradio] dB or dBm

How could I generate this simple sinusoidal signal with fixed frequency and
amplitude using Anritsu MG3710A?



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Re: [Discuss-gnuradio] dB or dBm

[GNUBeginner]

How could I generate this simple sinusoidal signal with fixed frequency and
amplitude using Anritsu MG3710A?



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Re: [Discuss-gnuradio] dB or dBm

[Gilad Beeri (ApolloShield)]

Yes - he meant a constant tone, a simple sinusoidal signal with fixed
frequency and amplitude (Acos(wt)).

And you can't measure the power directly. What you can measure is the graph
(function) between the injected power (as determined in your signal source)
to those strange dB values. After you get to the best function you can get,
you conclude power of other signals by comparing those dB values. As said,
you need to be aware of the different frequencies and gain values.



On Wed, Jun 21, 2017 at 9:04 PM GNUBeginner  wrote:

> Also, how could I measure power? The program is giving some strange dB
> values...
>
>
>
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Re: [Discuss-gnuradio] dB or dBm

[Ron Economos]

-20 dBm is a pretty strong signal. You're probably over driving your SDR 
into compression. I would use a larger value attenuator or reduce the 
levels from the signal generator.


Ron

On 06/21/2017 08:55 AM, GNUBeginner wrote:

Thank you for your detailed message. Please correct me if I am on the wrong
path.

I am injecting 802.11g signal using Vector Signal Generator at different
power levels (0 dBm, -5 dBm, -10 dBm, -15 dBm and -20 dBm) using 20 dB
attenuator. After running gr-scan with RF gain 0 dB option at the first
center frequency for this OFDM signal which is 2412 MHz, I am seeing the
following dB results respectively:

-49.37 dB
-49.54 dB
-50.23 dB
-53.58 dB
-58.52 dB

I am also planning to continue the same experiment using the other two
center frequency options which are 2437 MHz and 2462 MHz.

I would appreciate if you could please tell me what I am doing wrong. I am
using modified gr-scan code which has the RF Gain option included by zelfie.

Thanks



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Re: [Discuss-gnuradio] dB or dBm

[GNUBeginner]

Also, how could I measure power? The program is giving some strange dB
values...



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Re: [Discuss-gnuradio] dB or dBm

[GNUBeginner]

When you say constant tone, you mean some sinusoidal signal with fixed
frequency using Anritsu vector signal generator? Any suggestions generating
this signal with VSG?



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Re: [Discuss-gnuradio] dB or dBm

[Julian Arnold]

Hey,

as has been said previously, it depends on the type of signal you are
observing how you would need to characterize and measure its power.
For example, your signal will change over time depending on your payload
data which you need to consider. You would also need to consider the
bandwidth of the signal as it is not just made up of one peak in the
frequency domain.

I would try something simpler at the beginning. Generate a constant tone
at a fixed frequency and try to measure its power first.
Than, you can think about more complex signals.

Cheers,

On 06/21/2017 05:55 PM, GNUBeginner wrote:
> Thank you for your detailed message. Please correct me if I am on the wrong
> path.
>
> I am injecting 802.11g signal using Vector Signal Generator at different
> power levels (0 dBm, -5 dBm, -10 dBm, -15 dBm and -20 dBm) using 20 dB
> attenuator. After running gr-scan with RF gain 0 dB option at the first
> center frequency for this OFDM signal which is 2412 MHz, I am seeing the
> following dB results respectively:
>
> -49.37 dB
> -49.54 dB
> -50.23 dB
> -53.58 dB
> -58.52 dB
>
> I am also planning to continue the same experiment using the other two
> center frequency options which are 2437 MHz and 2462 MHz.
>
> I would appreciate if you could please tell me what I am doing wrong. I am
> using modified gr-scan code which has the RF Gain option included by zelfie.
>
> Thanks
>
>
>
> --
> View this message in context: 
> http://gnuradio.4.n7.nabble.com/dB-or-dBm-tp64323p64327.html
> Sent from the GnuRadio mailing list archive at Nabble.com.
>
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-- 
Julian Arnold, M.Sc.

Institute for Networked Systems
RWTH Aachen University

Kackertstrasse 9
52072 Aachen
Germany


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Re: [Discuss-gnuradio] dB or dBm

[GNUBeginner]

Thank you for your detailed message. Please correct me if I am on the wrong
path.

I am injecting 802.11g signal using Vector Signal Generator at different
power levels (0 dBm, -5 dBm, -10 dBm, -15 dBm and -20 dBm) using 20 dB
attenuator. After running gr-scan with RF gain 0 dB option at the first
center frequency for this OFDM signal which is 2412 MHz, I am seeing the
following dB results respectively:

-49.37 dB
-49.54 dB
-50.23 dB
-53.58 dB
-58.52 dB

I am also planning to continue the same experiment using the other two
center frequency options which are 2437 MHz and 2462 MHz.

I would appreciate if you could please tell me what I am doing wrong. I am
using modified gr-scan code which has the RF Gain option included by zelfie.

Thanks



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[Discuss-gnuradio] Changing transmit gain

[Tellrell White]

Hello Guys
I have a flowgraph attached where I'm trying to generate BER curves for
different transmit gain values. Right now, I have gui slider that allows me
to adjust the gain values, however, I would like to know if it's possible
to have the gain values adjust automatically by changing the python script
for the flowgraph. If so, I would appreciate any ideas or examples on how
to do this.

Thanks
Tellrell White
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Re: [Discuss-gnuradio] dB or dBm

[Gilad Beeri (ApolloShield)]

Marcus explained it better than me in your previous email, but in general,
those SDR devices aren't calibrated devices, as in you (the user) can't
infer from the sample value the signal power, so the apps (e.g.,
QSpectrumAnalyzer) can't tell you anything about dBm (power) values, only
dB values relative to some point (full scale according to Marcus).

If you want to measure the power values with those SDR devices, you need to
calibrate them by fixing the center frequency and the gain, then injecting
different levels of power, measuring the dB values you get, and inferring
the "dBm vs. dB-level" function (which depends on the center frequency and
gain, and possibly other factors).


On Wed, Jun 21, 2017 at 5:09 PM GNUBeginner  wrote:

> Hello Everybody,
>
> Could anyone please try to explain to me why I am seeing dB values instead
> of dBm in the spectrum analyzer GUIs such as QSpectrumAnalyzer or spectrum
> scan programs such as gr-scan or hackrf_sweep.
>
> Because when I inject a signal with -15 dBm power using 20 dB attenuator
> (no
> loss - just a short cable from the Vector Signal Generator to the HackRF
> One) to the HackRF One, somehow I see -53 dB as peak power.
>
> Thanks
>
>
>
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[Discuss-gnuradio] dB or dBm

[GNUBeginner]

Hello Everybody,

Could anyone please try to explain to me why I am seeing dB values instead
of dBm in the spectrum analyzer GUIs such as QSpectrumAnalyzer or spectrum
scan programs such as gr-scan or hackrf_sweep. 

Because when I inject a signal with -15 dBm power using 20 dB attenuator (no
loss - just a short cable from the Vector Signal Generator to the HackRF
One) to the HackRF One, somehow I see -53 dB as peak power.

Thanks 



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Re: [Discuss-gnuradio] Rational Resampler no output.

[Cor Legemaat]

Hi:

Sorry for the late replay... The intel pc call filter.firdes.low_pass
with the same values but return 768 proper float values, not like the
's on the AMD pc.

Tried to debug with "nemiver /usr/bin/python2.7 -u
/fm_receiver.py" and the breakpoint at firdes.cc line 100 witch
get triggered and I can read the function parameters but when I try to
step true the function it jumps to the assembly of pthread. If I put
more breakpoints in firdes.cc I get back to the function but cant read
any variables any more. Also tried exporting "export GR_SCHEDULER=STS"
but the same symptoms.

Don't know if Ubuntu will trigger the bug it's probably compiled more
generic...

Regards:
Cor

On Wed, 2017-06-07 at 04:26 -0400, Anon Lister wrote:
> > > I have an AMD system with the same chip running Ubuntu 16.xx. I can
probably try to duplicate this weekend, if Cor doesn't get to it, as
another data point. 
> 
> > > On Jun 5, 2017 3:14 PM, "Marcus Müller" 
wrote:
> 
>   
> 
>   
>   
> Hi Cor,
> 
> 
> Excuse the language, but frk. Ok, looks like we have a bug in
>   low_pass. Or in GCC. Or SWIG (which does the python-wrapping of
>   the code in firdes.cc). yay.
> So, let's narrow this down: on intel and amd64, same number of
>   taps, right?
> Then: If I asked you to use GDB to verify the C++ low_pass
>   function in gr::filter::firdes::low_pass actually returned the
> >   right float values, would you feel that, with a few hints, be
able
>   to do that?
> Best regards,
> Marcus
> 
> 
> 
> 
> On 01.06.2017 07:20, Cor Legemaat
>   wrote:
> 
> 
> 
> >   Hi:
> > 
> > filter.firdes.low_pass get called with:
> >  * fractional_bw = 0.4
> >  * trans_width = 0.1
> >  * mid_transition_band = 0.45
> >  * interpolation = 24
> > 
> > But return: (nan, <788 times nan>)
> > 
> > Regards:
> > Cor
> > 
> > On Tue, 2017-05-30 at 00:06 +0200, Marcus Müller wrote:
> > 
> > > Hi Cor,
> > > 
> > > >    * When using 1 as "taps" there is output.
> > > > 
> > >  Aha!!
> > > > > > So, here's the thing: something might be going wrong in the
python
> > > code that sets up the taps automatically if you don't set them
> > > explicitly. 
> > > > > > Maybe you can figure out where things go wrong; the interesting
part
> > > (maybe add some `print`s here?) from [1]:
> > > 
> > > > > >     # If we don't have user-provided taps, reduce the interp
and
> > > > > >     # decim values by the GCD (if there is one) and then
define
> > >     # the taps from these new values.
> > >     if taps is None:
> > >     interpolation = interpolation // d
> > >     decimation = decimation // d
> > >     taps = design_filter(interpolation, decimation,
> > > fractional_bw)
> > > 
> > > and
> > > 
> > > 
> > > def design_filter(interpolation, decimation, fractional_bw):
> > >     """
> > > > > >     Given the interpolation rate, decimation rate and a
fractional
> > > bandwidth,
> > >     design a set of taps.
> > > 
> > >     Args:
> > >     interpolation: interpolation factor (integer > 0)
> > >     decimation: decimation factor (integer > 0)
> > > > > >     fractional_bw: fractional bandwidth in (0, 0.5)  0.4
works
> > > well. (float)
> > >     Returns:
> > >     : sequence of numbers
> > >     """
> > > 
> > >     if fractional_bw >= 0.5 or fractional_bw <= 0:
> > > > > >     raise ValueError, "Invalid fractional_bandwidth, must be
in
> > > (0, 0.5)"
> > > 
> > >     beta = 7.0
> > >     halfband = 0.5
> > >     rate = float(interpolation)/float(decimation)
> > >     if(rate >= 1.0):
> > >     trans_width = halfband - fractional_bw
> > >     mid_transition_band = halfband - trans_width/2.0
> > >     else:
> > >     trans_width = rate*(halfband - fractional_bw)
> > >     mid_transition_band = rate*halfband - trans_width/2.0
> > > 
> > > > > >     taps =
filter.firdes.low_pass(interpolation,
> > > # gain
> > > > > >  
interpolation,
> > > # Fs
> > > > > >  
mid_transition_band,  
> > > # trans mid point
> > > > > >  
trans_width,  
> > > # transition width
> > >   filter.firdes.WIN_KAISER,
> > > > > >  
beta) 
> > > # beta
> > > 
> > >     return taps
> > > 
> > > 
> > > 
> > > Best regards,
> > > Marcus
> > > 
> > > > > > [1] https://github.com/gnuradio/gnuradio/blob/master/gr-filter/py
thon
> > > /filter/rational_resampler.py
> > > 
> > > On 29.05.2017 19:01, Cor Legemaat wrote:
> > > 
> > > >   Hi:
> > > > 
> > > >  * The only warning is about the thread priority but that's on
> > > > both.
> > > >  * Type "Complex->Complex (Complex Taps)"
> > > >  * When using 1 as "taps" there is output.
> > > > 
> > > > 

Re: [Discuss-gnuradio] Audio Source Sound Card L and R Channels

[Rob]

Thank-you Marcus the Audio Source is happy with 2 channels now.




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