On 03/25/2021 06:27 PM, Jerrid Plymale wrote:
Yes, moving TX out of the RX band has no affect on the noise level
increase.
Best Regards,
Jerrid
OK, so, let's get Gnu Radio out of the way.
Using the tx_waveforms UHD example (usually in
<prefix>/lib/uhd/examples) try sending a CW tone with a --ampl 1.0e-7,
and see what
happens.
Here's the --help output for tx_waveforms:
UHD TX Waveforms Allowed options:
--help help message
--args arg single uhd device address args
--spb arg (=0) samples per buffer, 0 for default
--nsamps arg (=0) total number of samples to transmit
--rate arg rate of outgoing samples
--freq arg RF center frequency in Hz
--ampl arg (=0.300000012) amplitude of the waveform [0 to 0.7]
--gain arg gain for the RF chain
--ant arg antenna selection
--subdev arg subdevice specification
--bw arg analog frontend filter bandwidth in Hz
--wave-type arg (=CONST) waveform type (CONST, SQUARE, RAMP, SINE)
--wave-freq arg (=0) waveform frequency in Hz
--ref arg (=internal) clock reference (internal, external, mimo,
gpsdo)
--pps arg PPS source (internal, external, mimo, gpsdo)
--otw arg (=sc16) specify the over-the-wire sample mode
--channels arg (=0) which channels to use (specify "0", "1",
"0,1",
etc)
--int-n tune USRP with integer-N tuning
*From:*Marcus D Leech <patchvonbr...@gmail.com>
*Sent:* Thursday, March 25, 2021 2:29 PM
*To:* Jerrid Plymale <jerrid.plym...@canyon-us.com>
*Cc:* USRP-users@lists.ettus.com
*Subject:* Re: [USRP-users] Strong noise added to signal transmitted
by X310 with a UBX 40 daughterboard
If you move the TX out of band with respect to the RX do you still see
the noise when the TX graph starts?
Sent from my iPhone
On Mar 25, 2021, at 3:57 PM, Jerrid Plymale
<jerrid.plym...@canyon-us.com
<mailto:jerrid.plym...@canyon-us.com>> wrote:
So I was able to test setting up both USRPs with the same 10 MHz
reference signal, and there was no improvement to the noise being
added.
If the flowgraph just emits a CW tone, we see a similar response,
the added noise is still there and at the same level, we just have
the added spike of the CW tone at the frequency we set it to.
Best Regards,
Jerrid
*From:*Marcus D Leech <patchvonbr...@gmail.com
<mailto:patchvonbr...@gmail.com>>
*Sent:* Wednesday, March 24, 2021 5:01 PM
*To:* Jerrid Plymale <jerrid.plym...@canyon-us.com
<mailto:jerrid.plym...@canyon-us.com>>
*Cc:* USRP-users@lists.ettus.com <mailto:USRP-users@lists.ettus.com>
*Subject:* Re: [USRP-users] Strong noise added to signal
transmitted by X310 with a UBX 40 daughterboard
You don’t need 1PPS for this. Having an external high quality
reference may help, assuming my guess about your issue is correct.
What happens if your flow graph just simply emits a Cw tone, using
the mute function perhaps tied to a GUI control or some such.
Sent from my iPhone
On Mar 24, 2021, at 7:13 PM, Jerrid Plymale
<jerrid.plym...@canyon-us.com
<mailto:jerrid.plym...@canyon-us.com>> wrote:
Ok, if that’s the case, would it help to have both USRPs
connected to the same 10 MHz reference signal and PPS? In this
situation, would I need to provide a secondary source for the
PPS, or can that use the 10 Mhz reference as well?
Best Regards,
Jerrid
*From:*Marcus D. Leech <patchvonbr...@gmail.com
<mailto:patchvonbr...@gmail.com>>
*Sent:* Wednesday, March 24, 2021 2:23 PM
*To:* Jerrid Plymale <jerrid.plym...@canyon-us.com
<mailto:jerrid.plym...@canyon-us.com>>
*Cc:* USRP-users@lists.ettus.com
<mailto:USRP-users@lists.ettus.com>
*Subject:* Re: [USRP-users] Strong noise added to signal
transmitted by X310 with a UBX 40 daughterboard
On 03/24/2021 05:10 PM, Jerrid Plymale wrote:
The devices are operating using direct connection via coax
cables.
You absolutely need to put a 30dB attenuator in-line to
prevent RX destruction in the case of "ooops" moments from
setting the TX
power output too high.
The target frequency is 1.57542 GHz, and our current
bandwidth is 4 MHz. We will need to increase the bandwidth
to 20 MHz soon for further system development.
The TX and RX gain are maxed on the receiving hardware.
The TX gain of the transmitting hardware is set to 0, as
at max the noise strength increases to ~ 20 dB.
Attached are images of the FFT provided by the Frequency
Sink in Gnuradio. Hopefully these give a visual aid for
the problem at hand. When I have the transmitter USRP
turned off (image 1), it would seem like the noise floor
coming into the USRP is around -94 dB. When the
transmitter is turned on and the flowgraph is started with
the transmitted signal muted (I am using a python block
with code to create custom signals that is then connected
to a mute block that then connects to the UHD USRP sink
block to be able to mute the signal during runtime), the
noise floor increases to around -78 dB.
Best Regards,
Jerrid
You are likely just seeing the LO leakage, along with the
inevitable phase-noise curve of the LO.
*From:* Marcus D Leech <patchvonbr...@gmail.com>
<mailto:patchvonbr...@gmail.com>
*Sent:* Wednesday, March 24, 2021 11:58 AM
*To:* Jerrid Plymale <jerrid.plym...@canyon-us.com>
<mailto:jerrid.plym...@canyon-us.com>
*Cc:* USRP-users@lists.ettus.com
<mailto:USRP-users@lists.ettus.com>
*Subject:* Re: [USRP-users] Strong noise added to signal
transmitted by X310 with a UBX 40 daughterboard
Is the j B is over-the-air or direct connection?
What frequency? Bandwidth?
Do you have TX and RX gain turned all the way up?
Can you share your flow-graphs, or minimum
Graphs that show the problem?
Sent from my iPhone
On Mar 24, 2021, at 12:20 PM, Jerrid Plymale
<jerrid.plym...@canyon-us.com
<mailto:jerrid.plym...@canyon-us.com>> wrote:
Hello All,
I have been running tests in which I am transmitting a
signal from one USRP X310 that’s using a UBX 40
daughterboard, and that signal is being received by
another USRP X310 using a UBX 40 daughterboard. I have
noticed that when I have the receiving USRP running
with the Gnuradio flowgraph active, as soon as I start
the transmitting USRP’s Gnuradio flowgraph, there is a
jump in the noise floor as it is seen by the receiving
USRP, and its roughly a 14 dB increase. This occurs
even if I have the signal being transmitted muted.
Does anyone have any idea what the source of this
added noise could be? It is something that I need to
mitigate as much as possible for the tests I am
running using these USRPs. Any feedback will be
greatly appreciated, thanks!
Best Regards,
Jerrid
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