Hi Robin and Marcus,
Thanks for your hints.
UHD 3.14.1.1 work perfectly fine with my X310s. Only the N310s seem to
have problems. I use the default HG FPGA image that ships with 3.14.1.1.
For the moment, I use `VERT2450` antennas. The ones you can order from
Ettus. I transmit/receive @2.484GHz. I mounted antennas on all antenna
ports. So for the N310s that's a total of 8 antennas per device.
So far I did not specify a `Subdev Spec` in GRC.
I tried a few more options. Also, I unmounted the antennas on the RX2
ports on the N310s and made sure the `TX/RX` antenna port is configured.
Here are my observations:
1. X310 -> X310 everything works fine TXgain=20, RXgain=10.
2. N310 -> X310 everything works, though I need to raise TXgain=38 a bit.
3. X310 -> N310 works but it seems like sensitivity is still bad. I need
to raise TXgain=70. RXgain seems to not make a difference at all.
4. N310 -> N310 bad performance but transmission is possible. Need to
raise gains to almost maximum for bad performance.
This is the N310 setup code generated by GRC. I tried different `Subdev
Spec`s for both TX and RX. I obtained the best results with `B:0` for TX
and RX. Though, `best` is still way worse than X310 performance.
uhd.usrp_source(
",".join(("addr=X.X.X.214", "")),
uhd.stream_args(
cpu_format="fc32",
args='',
channels=[],
),
)
self.uhd_usrp_source_0.set_subdev_spec('B:0', 0)
self.uhd_usrp_source_0.set_center_freq(tfreq, 0)
self.uhd_usrp_source_0.set_gain(rgain, 0)
self.uhd_usrp_source_0.set_antenna('TX/RX', 0)
self.uhd_usrp_source_0.set_samp_rate(samp_rate)
Since Option 2 N310 -> X310 does yield good results, I assume that the
N310 RX chain or configuration is the problem. Though, I have no idea
how to debug that and which knobs to turn.
I tried to observe the spectrum with an N310 via `uhd_fft` from
`gr-uhd/examples/grc` and it feels like the N310 just doesn't case about
RXgain settings.
Johannes
On 18.10.19 20:42, Marcus D Leech wrote:
> What antenna are you specifying and which port are you rurally plugged in to.
>
> Are you using offset tuning? That may be necessary for Narrow signals near
> the tuned frequency, due to DC offset removal.
On 18.10.19 16:24, Robin Coxe wrote:
> Hi Johannes. That low response from the N310 sounds fishy. Have you
> tried another channel besides 0 on your N310? It might be that: 1) the
> TX and RX cables are connected backwards (note that the order on the
> panel is funky due to layout constraints with the AD9371 RF IC on the
> daughter cars. 2) signals are actually on the adjacent channel—
> double-check the UHD subdev mappings listed in the Getting Started Guide
> because if memory serves they changed at some point— or 3) or the SMA
> connector center pin connections might be cracked.
>
> Also, I’m not sure how compatible GR3.8 is with UHD 3.14.1. Someone
> who still works on Ettus products mentioned at GRCon that you have to
> use master-next branches, but those use the new RFNoC, which is still
> largely uncharted territory with the N310 as far as I can tell.
>
> -Robin
>
>
> ------------------------------------------------------------------------
> *From:* USRP-users <[email protected]> on behalf of
> Johannes Demel via USRP-users <[email protected]>
> *Sent:* Friday, October 18, 2019 4:06 AM
> *To:* [email protected]
> *Subject:* [USRP-users] N310 sensitivity
> Hi all,
>
> I figured out how to use our new N310s.
>
> I ran into the next issue. Let me describe this one briefly.
>
> With our X310s I set TXgain=20 and RX_gain=10. Both devices are 1-2m
> apart. I observe a really nice RX constellation with gr-gfdm and
> XFDMSync with bursts every 1ms (burst length ~50us). With our N310s I
> set RXgain=60, TXgain=70 and still, the constellation is very noisy.
> My assumption is that some part of the RX chain is not configured
> correctly. But I don't know what the problem is in particular.
> Also, I used an X310 as transmitter and an N310 as receiver. But the
> result is the same, the RX constellation is really noisy.
>
> Another observation is, that my RX sample stream in a GR time sink does
> show quantization artifacts. i.e. I can see discrete steps which I
> assume are due to low RX sensitivity. The RX value amplitude is around
> 0.0005 for the samples that I get of a USRP source. I assume this should
> be a higher value. With the X310s it was more like 0.1.
>
> Do I need to take special care when I only use 1 antenna port?
> Is there another AGC setting that I need to configure for N310s?
>
> Johannes
>
> Software
> UHD: 3.14.1.1
> GR: 3.8
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> USRP-users mailing list
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