On 08/03/2021 11:08 AM, Marcin Wachowiak wrote:
Hello,
The signals provided at the input have quite low power, far below the
threshold of -20dbm. ( I don't know the exact values but I
additionally even added a 30dB attenuator for safety)
What I also found out is that the distortions are dependent more on
the setting of the RX, TX gain than the value. During live testing I
observed the this harmonic distortion at one channel only, and after
increasing the TX or RX gain it disappeared (what is visible in the
new videos):
usrp_b210_strange_harmonic_distoriton.mp4
<https://drive.google.com/file/d/1hYHfI_oXke5K9PGTz-R88n-DNfaiJUYP/view?usp=drive_web>
usrp_b210_strange_harmonic_distoriton_2.mp4
<https://drive.google.com/file/d/15bq0hmUJFLWskA8qb7w_7-EXPF3oGv7Y/view?usp=drive_web>
Kind regards,
Marcin Wachowiak
Right because distortion in RF components isn't going to start occurring
at a uniform level over each discrete device--there will be variability.
Are you using the same (RX2) antenna inputs in each case? At high gain
levels it doesn't take much to drive things into non-linear operation.
On Mon, 2 Aug 2021 at 18:57, <[email protected]
<mailto:[email protected]>> wrote:
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Today's Topics:
1. Older B100 and associated Daughter cards. (Guy Mengel)
2. Re: Older B100 and associated Daughter cards. (Richard Stanley)
3. One RX channel of B210 presents distorted signal from splitter
(Marcin Wachowiak)
4. Re: One RX channel of B210 presents distorted signal from
splitter
(Marcus D. Leech)
----------------------------------------------------------------------
Message: 1
Date: Mon, 02 Aug 2021 09:47:18 -0400
From: Guy Mengel <[email protected] <mailto:[email protected]>>
Subject: [USRP-users] Older B100 and associated Daughter cards.
To: [email protected] <mailto:[email protected]>
Message-ID: <[email protected]
<mailto:[email protected]>>
Content-Type: text/plain; markup=markdown
Hi All,
I am finally going to get started using an older B100 USRP with
the LFTX, LFRX, WBX daughter boards. I purchased these from a
well known amateur radio op in January of this year. I had played
with it for a short time on Ubuntu 18.04 with the older
unsupported Python2 interface, this was a start. Then the Covid
Pandemic hit.
Well, I am now back.
Are there any users in the group using the B100 USRP with the
LFTX, LFRX, WBX daughter boards using a newer Ubuntu 20.04 with
updated Python 3.X with GNURADIO? I wanted to see if there were
any still using this older SDR. My plans are to experiment with
it and create a rig to be used at HF and possibly UHF to microwave
down the road.
I would also like to have pointers too!
Thanks!
Guy Mengel N1GMM
------------------------------
Message: 2
Date: Mon, 2 Aug 2021 10:37:14 -0400
From: Richard Stanley <[email protected]
<mailto:[email protected]>>
Subject: [USRP-users] Re: Older B100 and associated Daughter cards.
To: Guy Mengel <[email protected] <mailto:[email protected]>>
Cc: [email protected] <mailto:[email protected]>
Message-ID: <[email protected]
<mailto:[email protected]>>
Content-Type: text/plain; charset=us-ascii
(Resent to include mailing list)
Hi Guy,
I've recently used B100s with the LFRX, BasicRX, and (EOL) TVRX2
with the latest UHD and GNU Radio 3.8 on Ubuntu 20.04.
A challenge for me with the LFRX/TX and BasicRX/TX was finding the
correct sub-device specification as they can acquire/transmit an
IQ pair or real-valued signals. In addition, I required a Hilbert
transform to convert real-valued samples in baseband to complex
for some processing in GNU Radio for Rx. There are a lot of
questions about these daughtercards in the mailing list archive
and often the questions seem to be about sub-device specification
and real-valued versus IQ.
Enjoy the B100!
HTH,
Richard
On Aug 2, 2021, at 09:47, Guy Mengel <[email protected]
<mailto:[email protected]>> wrote:
Hi All,
I am finally going to get started using an older B100 USRP with
the LFTX, LFRX, WBX daughter boards. I purchased these from a
well known amateur radio op in January of this year. I had played
with it for a short time on Ubuntu 18.04 with the older
unsupported Python2 interface, this was a start. Then the Covid
Pandemic hit.
Well, I am now back.
Are there any users in the group using the B100 USRP with the
LFTX, LFRX, WBX daughter boards using a newer Ubuntu 20.04 with
updated Python 3.X with GNURADIO? I wanted to see if there were
any still using this older SDR. My plans are to experiment with
it and create a rig to be used at HF and possibly UHF to microwave
down the road.
I would also like to have pointers too!
Thanks!
Guy Mengel N1GMM
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To unsubscribe send an email to [email protected]
<mailto:[email protected]>
------------------------------
Message: 3
Date: Mon, 2 Aug 2021 18:37:08 +0200
From: Marcin Wachowiak <[email protected]
<mailto:[email protected]>>
Subject: [USRP-users] One RX channel of B210 presents distorted signal
from splitter
To: [email protected] <mailto:[email protected]>
Message-ID:
<caofh71xdrz7a+xu89t-6gewy4aa_hmnfb+-0aege6y-f4zv...@mail.gmail.com <mailto:caofh71xdrz7a%2bxu89t-6gewy4aa_hmnfb%[email protected]>>
Content-Type: multipart/alternative;
boundary="000000000000d8512b05c8962e2b"
Hello,
I am working on a phase coherent application using USRP B210. As
the phase
difference between RX channels of B210 is relatively stable I
wanted to see
how it behaves across the whole frequency range. I performed some
measurements and unfortunately for some frequencies I observed strange
distortions. The setup consists of a TX USRP, RF splitter, matched
cables
and a second USRP with both RX channels connected to the splitter.
Screams documenting the distortions:
https://drive.google.com/drive/folders/1DkjrVKz3ywv3ZE0eS1UYeCMTtQwL3Du8?usp=sharing
The received sine wave should have quite similar shape and spectral
properties across both RX channels of USRP.
What I observe instead is a symmetrical harmonic tone at one of
the RX,
when the other does not record it.
There are also random distortions in one of the RX channels
looking as if
the sine signal was split and shifted at some point in time (looks
like a
some sort of buffer issue)
This kind of distortion for some settings persists for some is not
present
or occurs regularly.
To provide some illustiation I attach recordings and screens of the
registered distortions.
usrpb210_sine_rx_distoriton2.mp4
<https://drive.google.com/file/d/1Hif0dZY2Ah7ipC13nfudhoK5HD0JeM9M/view?usp=drive_web>
usrpb210_sine_rx_distoriton.mp4
<https://drive.google.com/file/d/13niyBdl6H4w0Akdf28KeontnZKUsCUaW/view?usp=drive_web>
I tried to debug this problem but it appears to be related to
sample rate,
TX tone frequency, carrier frequency and gains. (I checked dynamic IQ
imbalance or gain controls and changing of the parameters did not
affect
anything)
There are now underflow/overflow flags present while I run the
flowchart.
The signal that is provided to both RX is identical ( RF
mini-circuits RF
splitter), and any outside interferences are limited as the whole
setup is
connected via concentric cables. I tried to set the number of
receive and
sent frames to 1024 to ensure continuity, but that didn't help.
It is strange that for some frequencies this phenomenon occurs
while for
others the phase difference variance is very low and there are no such
distortions.
Could You please explain the cause or propose some kind of
solution to this
issue?
Kind regards,
Marcin Wachowiak
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Message: 4
Date: Mon, 02 Aug 2021 12:39:31 -0400
From: "Marcus D. Leech" <[email protected]
<mailto:[email protected]>>
Subject: [USRP-users] Re: One RX channel of B210 presents distorted
signal from splitter
To: [email protected] <mailto:[email protected]>
Message-ID: <[email protected]
<mailto:[email protected]>>
Content-Type: multipart/alternative;
boundary="------------050204020106080302070102"
On 08/02/2021 12:37 PM, Marcin Wachowiak wrote:
> Hello,
> I am working on a phase coherent application using USRP B210. As
the
> phase difference between RX channels of B210 is relatively stable I
> wanted to see how it behaves across the whole frequency range. I
> performed some measurements and unfortunately for some
frequencies I
> observed strange distortions. The setup consists of a TX USRP, RF
> splitter, matched cables and a second USRP with both RX channels
> connected to the splitter.
> Screams documenting the distortions:
>
https://drive.google.com/drive/folders/1DkjrVKz3ywv3ZE0eS1UYeCMTtQwL3Du8?usp=sharing
> The received sine wave should have quite similar shape and spectral
> properties across both RX channels of USRP.
> What I observe instead is a symmetrical harmonic tone at one of the
> RX, when the other does not record it.
> There are also random distortions in one of the RX channels
looking as
> if the sine signal was split and shifted at some point in time
(looks
> like a some sort of buffer issue)
> This kind of distortion for some settings persists for some is not
> present or occurs regularly.
> To provide some illustiation I attach recordings and screens of the
> registered distortions.
> usrpb210_sine_rx_distoriton2.mp4
>
<https://drive.google.com/file/d/1Hif0dZY2Ah7ipC13nfudhoK5HD0JeM9M/view?usp=drive_web>
> usrpb210_sine_rx_distoriton.mp4
>
<https://drive.google.com/file/d/13niyBdl6H4w0Akdf28KeontnZKUsCUaW/view?usp=drive_web>
>
> I tried to debug this problem but it appears to be related to
sample
> rate, TX tone frequency, carrier frequency and gains. (I checked
> dynamic IQ imbalance or gain controls and changing of the
parameters
> did not affect anything)
> There are now underflow/overflow flags present while I run the
> flowchart. The signal that is provided to both RX is identical ( RF
> mini-circuits RF splitter), and any outside interferences are
limited
> as the whole setup is connected via concentric cables. I tried
to set
> the number of receive and sent frames to 1024 to ensure continuity,
> but that didn't help.
> It is strange that for some frequencies this phenomenon occurs
while
> for others the phase difference variance is very low and there
are no
> such distortions.
> Could You please explain the cause or propose some kind of
solution to
> this issue?
>
> Kind regards,
> Marcin Wachowiak
>
>
> _______________________________________________
> USRP-users mailing list -- [email protected]
<mailto:[email protected]>
> To unsubscribe send an email to [email protected]
<mailto:[email protected]>
What are your signal levels going into the RX USRP?
They need to be well below -20dBm or so to protect against
non-linearity, and even then, that's awfully loud.
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