On 10/10/2018 03:08 PM, Ali Dormiani via USRP-users wrote:
Hello,
We have the exact same problem. My lab is waiting on some sfp+ cables
so in a few days I will share our screenshots, code, and data binary
files in order to provide this thread with a second example of this
issue. For now, all I can say is this problem is not isolated to your
N310 or Windows.
We have two N310's running with the same version of UHD (and GNUradio
3.7.13.4) on Linux kernel 4.18. By using amplitude sliders in GNUradio
we found that there is a very small and strange gain "Goldilocks" zone
around .002 that gives good results. Going higher starts to raise the
noise floor until all signal definition is gone.
Ali Dormiani
UCSD Noiselab
What is your RF gain set to in these examples? Does that change things?
If you raise things to a level where non-linearity is apparent, does
placing a 10dB attenuator in-line fix it (trying to distinguish between
the transmitter being non-linear, and your receiver/spectrum analyser).
On Wed, Oct 10, 2018 at 11:33 AM Mathieu Lizée via USRP-users
<usrp-users@lists.ettus.com <mailto:usrp-users@lists.ettus.com>> wrote:
Hi,
When using the UHD "tx_waveforms" example, I can see that the
signal emitted by my N310 USRP is saturated when it’s not supposed
to be.
Here's a snapshot of the signal when I set the amplitude to 0.003:
|.\tx_waveforms.exe --rate 12.5e6 --nsamps 1250000000 --freq
1575.42e6 --ampl 0.003 --otw sc16 --wave-type SINE --wave-freq
10e3 --channels 2|
tx_waveforms_3e-3_amp
<https://user-images.githubusercontent.com/15334138/46685506-a7424700-cbc3-11e8-926e-b0da5f416652.png>
Here's a snapshot of the signal when I set the amplitude to 0.03:
|.\tx_waveforms.exe --rate 12.5e6 --nsamps 1250000000 --freq
1575.42e6 --ampl 0.03 --otw sc16 --wave-type SINE --wave-freq 10e3
--channels 2|
tx_waveforms_3e-2_amp
<https://user-images.githubusercontent.com/15334138/46685468-9265b380-cbc3-11e8-9ce7-42908cf9bf2e.png>
As you can see from the pictures above, it seems that there's a
saturation in the signal when the amplitude is set to 0.03 (which
is unexpected with such a small amplitude). We have double-checked
with a X300 device, and the signal is normal in both cases.
Do you have an idea of what could be wrong, or a suggestion to try
on our side?
Technical Information:
* Windows 10
* USRP N310
* UHD 3.13.0.3-rc1
Thank you!
--
*Mathieu Lizee*
/Software Development Intern/
*Skydel Solutions*
WeWork 5th Floor (Skydel)
1275 Av des Canadiens-de-Montreal
Montreal, QC
H3B 0G4
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