4 Sep
2020
4 Sep
'20
2:53 a.m.
Trying to test out an AIRSPY R2 and the signal level v. an RTL is not
even close.
I've got -N options for LNA, MIX, IF, but what is the option for the
MASTER GAIN?
I've tried MAS, MASTER in the -N option, no change in the signal.
I've tried -g as well no joy.
Example:
./rx.py --args 'airspy' -N 'MASTER:50,IF:10,MIX:5,LNA:50' -S 2500000
-f 769.55625e6 -v 7 -T P25PC.tsv -q 2 -V -2 -U -x 2 2>> airspy.log
./rx.py --args 'airspy' -N 'IF:10,MIX:5,LNA:15' -S 2500000 -f
774.55625e6 -v 7 -T P25PC.tsv -q 2 -V -2 -U -x 2 2>> airspy.log
What is the CORRECT method to set the MASTER GAIN of the Airspys,
using something else its set to 14 for a good signal.
Thanks.
4 Sep
4 Sep
3:10 a.m.
I'm not aware of a master gain parameter. LNA, MIX, IF are the three gain
controls. All take value between 0-15.
Graham
On Thu, Sep 3, 2020, 9:00 PM <op25(a)zellners.com> wrote:
Trying to test out an AIRSPY R2 and the signal level v. an RTL is not
even close.
I've got -N options for LNA, MIX, IF, but what is the option for the
MASTER GAIN?
I've tried MAS, MASTER in the -N option, no change in the signal.
I've tried -g as well no joy.
Example:
./rx.py --args 'airspy' -N 'MASTER:50,IF:10,MIX:5,LNA:50' -S 2500000
-f 769.55625e6 -v 7 -T P25PC.tsv -q 2 -V -2 -U -x 2 2>> airspy.log
./rx.py --args 'airspy' -N 'IF:10,MIX:5,LNA:15' -S 2500000 -f
774.55625e6 -v 7 -T P25PC.tsv -q 2 -V -2 -U -x 2 2>> airspy.log
What is the CORRECT method to set the MASTER GAIN of the Airspys,
using something else its set to 14 for a good signal.
Thanks.
12:34 p.m.
Quoting Graham Norbury <gnorbury(a)bondcar.com>om>:
I'm not aware of a master gain parameter. LNA,
MIX, IF are the three gain
controls. All take value between 0-15.
Ummm...mmm...hmmmmmm...
SDRTrunk exposes:
4 CONTROLS and 3 options in a drop down.
A guess is these "modes" are some sort of custom setup? As you can set
CUSTOM MODE and you can then adjust IF,MIX,LNA separately... in
SENSITIVITY or LINEARITY MODES it has a "MASTER" slider which I will
take it that if there really are only 3 real gains must be a custom
adjust to all 3 via that slider???? Which it doesn't reflect in the
GUI that its adjusting them.... but thats not really relevant here.
I am trying to match performance from an RTL to the Airspy, and the
plot on the spectrum is at least 20db down from the RTL (RTL Gain
49)..unless the Airspys are significantly less sensitive which SDRT
doesn't seem to show.
I get -20db power level with the RTL and and the airspy is at
-40db...and playing with those gains didn't seem to budge it... hmmm..
I'll give another whack tonight using only the 3 controls and see what
I get...
Thanks...
5 Sep
5 Sep
1:23 p.m.
Quoting Graham Norbury <gnorbury(a)bondcar.com>om>:
I'm not aware of a master gain parameter. LNA,
MIX, IF are the three gain
controls. All take value between 0-15.
>
> ./rx.py --args 'airspy' -N 'IF:10,MIX:5,LNA:15' -S 2500000 -f
> 774.55625e6 -v 7 -T P25PC.tsv -q 2 -V -2 -U -x 2 2>> airspy.log
I reran my tests on this again, using -N 'IF:,MIX:,LNA:' like above
with 0-15 values.
The spike for the CC, as a test, didn't budge at all, all 15, or
anything in between, no changes.
It is significantly lower to start -20 to -40db lower v. other
programs and depending on antenna.
Its almost like the gains are set to 0 or something and never
change??? ? ? ? ?
Even using a duck direct to the Airspy with another program results in
much higher signals on its spectrum, and gains will adjust accordingly.
Changes will occur in another program with adjustments to all 3
(outside its faked single slider mode, using just the REAL GAINS),
gains shows changes in the signals and noise floor.
In op25, not a bit of change at all in any thing. noise or signal.
Like these are not being sent? Or not taking affect?? ? ? 15 for all,
combos of values, even things like 50 for all three, no changes.
I am not sure what to even try at this point? Other than missing lib
when it was compiled??? I didn't have the airspy then or airspy
pacakges installed when compiled.. does that change anything??? It
seems to work regardless of that, it tunes, it will trunk, voice etc.,
just the gains don't seem to do a thing at all. IF there was something
missing in this, I would expect it to fail to tune, audio etc..
Ideas?????
2:25 p.m.
This happens when the agc is turned on. Bill Becks and I experimented with
it a while back and found a way to enable/disable, but at this moment I
don't recall the magic incantation.
Graham
On Sat, Sep 5, 2020, 7:23 AM <op25(a)zellners.com> wrote:
Quoting Graham Norbury <gnorbury(a)bondcar.com>om>:
I'm not aware of a master gain parameter.
LNA, MIX, IF are the three
gain
controls. All take value between 0-15.
>
> ./rx.py --args 'airspy' -N 'IF:10,MIX:5,LNA:15' -S 2500000 -f
> 774.55625e6 -v 7 -T P25PC.tsv -q 2 -V -2 -U -x 2 2>> airspy.log
I reran my tests on this again, using -N 'IF:,MIX:,LNA:' like above
with 0-15 values.
The spike for the CC, as a test, didn't budge at all, all 15, or
anything in between, no changes.
It is significantly lower to start -20 to -40db lower v. other
programs and depending on antenna.
Its almost like the gains are set to 0 or something and never
change??? ? ? ? ?
Even using a duck direct to the Airspy with another program results in
much higher signals on its spectrum, and gains will adjust accordingly.
Changes will occur in another program with adjustments to all 3
(outside its faked single slider mode, using just the REAL GAINS),
gains shows changes in the signals and noise floor.
In op25, not a bit of change at all in any thing. noise or signal.
Like these are not being sent? Or not taking affect?? ? ? 15 for all,
combos of values, even things like 50 for all three, no changes.
I am not sure what to even try at this point? Other than missing lib
when it was compiled??? I didn't have the airspy then or airspy
pacakges installed when compiled.. does that change anything??? It
seems to work regardless of that, it tunes, it will trunk, voice etc.,
just the gains don't seem to do a thing at all. IF there was something
missing in this, I would expect it to fail to tune, audio etc..
Ideas?????
2:45 p.m.
If you're using rx.py try setting "--gain-mode 0" on the command line.
That parameter is not implemented in multi_rx.py but if you change it in
one app (e.g. gqrx), it will persist in other apps until you power cycle
the airspy dongle.
Graham
On 9/5/20 8:25 AM, Graham Norbury wrote:
This happens when the agc is turned on. Bill Becks
and I experimented
with it a while back and found a way to enable/disable, but at this
moment I don't recall the magic incantation.
Graham
On Sat, Sep 5, 2020, 7:23 AM <op25(a)zellners.com
<mailto:op25@zellners.com>> wrote:
Quoting Graham Norbury <gnorbury(a)bondcar.com
<mailto:gnorbury@bondcar.com>>:
I'm not aware of a master gain parameter.
LNA, MIX, IF are the
three gain
controls. All take value between 0-15.
>
> ./rx.py --args 'airspy' -N 'IF:10,MIX:5,LNA:15' -S 2500000 -f
> 774.55625e6 -v 7 -T P25PC.tsv -q 2 -V -2 -U -x 2 2>> airspy.log
I reran my tests on this again, using -N 'IF:,MIX:,LNA:' like above
with 0-15 values.
The spike for the CC, as a test, didn't budge at all, all 15, or
anything in between, no changes.
It is significantly lower to start -20 to -40db lower v. other
programs and depending on antenna.
Its almost like the gains are set to 0 or something and never
change??? ? ? ? ?
Even using a duck direct to the Airspy with another program
results in
much higher signals on its spectrum, and gains will adjust
accordingly.
Changes will occur in another program with adjustments to all 3
(outside its faked single slider mode, using just the REAL GAINS),
gains shows changes in the signals and noise floor.
In op25, not a bit of change at all in any thing. noise or signal.
Like these are not being sent? Or not taking affect?? ? ? 15 for
all,
combos of values, even things like 50 for all three, no changes.
I am not sure what to even try at this point? Other than missing lib
when it was compiled??? I didn't have the airspy then or airspy
pacakges installed when compiled.. does that change anything??? It
seems to work regardless of that, it tunes, it will trunk, voice
etc.,
just the gains don't seem to do a thing at all. IF there was
something
missing in this, I would expect it to fail to tune, audio etc..
Ideas?????
3:29 p.m.
Gents,
Graham Norbury dug into the Airspy library sometime back and came up with a fix to
enable/disable the various gain modes. I want to recall that he patched some of the
existing code
to allow additional args to control these gain modes. So it’s likely the following will
only apply to the boatbod version of op25.
The yellow highlighted text below in my rx.py command line is an example of how my R2
device was set to manual gain mode whereby the device responds to user specified LNA, MIX,
and IF gain settings.
./rx.py --args "airspy=0,sensitivity=0,linearity=0,bias=0" -N
'LNA:15,MIX:15,IF:10' -S 2500000 -T trunk.tsv ………
Bill
From: op25-dev <op25-dev-bounces(a)lists.osmocom.org> On Behalf Of Graham Norbury
Sent: Saturday, September 5, 2020 7:25 AM
To: op25-dev(a)lists.osmocom.org
Subject: Re: [op25-dev] rx.py Airspy MASTER GAIN Setting option?????
This happens when the agc is turned on. Bill Becks and I experimented with it a while
back and found a way to enable/disable, but at this moment I don't recall the magic
incantation.
Graham
On Sat, Sep 5, 2020, 7:23 AM <op25(a)zellners.com <mailto:op25@zellners.com> >
wrote:
Quoting Graham Norbury <gnorbury(a)bondcar.com <mailto:gnorbury@bondcar.com> >:
I'm not aware of a master gain parameter. LNA,
MIX, IF are the three gain
controls. All take value between 0-15.
>
> ./rx.py --args 'airspy' -N 'IF:10,MIX:5,LNA:15' -S 2500000 -f
> 774.55625e6 -v 7 -T P25PC.tsv -q 2 -V -2 -U -x 2 2>> airspy.log
I reran my tests on this again, using -N 'IF:,MIX:,LNA:' like above
with 0-15 values.
The spike for the CC, as a test, didn't budge at all, all 15, or
anything in between, no changes.
It is significantly lower to start -20 to -40db lower v. other
programs and depending on antenna.
Its almost like the gains are set to 0 or something and never
change??? ? ? ? ?
Even using a duck direct to the Airspy with another program results in
much higher signals on its spectrum, and gains will adjust accordingly.
Changes will occur in another program with adjustments to all 3
(outside its faked single slider mode, using just the REAL GAINS),
gains shows changes in the signals and noise floor.
In op25, not a bit of change at all in any thing. noise or signal.
Like these are not being sent? Or not taking affect?? ? ? 15 for all,
combos of values, even things like 50 for all three, no changes.
I am not sure what to even try at this point? Other than missing lib
when it was compiled??? I didn't have the airspy then or airspy
pacakges installed when compiled.. does that change anything??? It
seems to work regardless of that, it tunes, it will trunk, voice etc.,
just the gains don't seem to do a thing at all. IF there was something
missing in this, I would expect it to fail to tune, audio etc..
Ideas?????
6 Sep
6 Sep
4:28 p.m.
Quoting wllmbecks(a)gmail.com:
The yellow highlighted text below in my rx.py command
line is an
example of how my R2 device was set to manual gain mode whereby the
device responds to user specified LNA, MIX,
and IF gain settings.
./rx.py --args "airspy=0,sensitivity=0,linearity=0,bias=0" -N
'LNA:15,MIX:15,IF:10' -S 2500000 -T trunk.tsv ………
Thanks... I think that may be the
magic,airspy=0,sensitivity=0,linearity=0,bias=0, as those names are
present in the other program, but hmm... I would expect since I nuked
them in that program it would persist? I guess not..
I will try this during some tests today... have to work on a more
mission critical option at first.
Thanks....
4:45 p.m.
Setting the manual gain mode in op25 will take away AGC and more importantly will
remove the false spike in the center of the spectrum. This is quite so that you can
visualize
the "Real" control channel from a figment of the Airspy's imagination.
Note that a full reboot or removal and re-plugging of the SDR into the USB port will be
required to clear the Airspy from previous linearity or sensitivity modes. Changing of
the
rx.py command line arguments and restarting rx.py will not clear the internal registers
of
the device, something that it took me a while to figure out.
I would still recommend starting with (-q 0) while checking for the presence of
TSBK's
coming from the control channel, and/or verification of a legitimate p25 signal by
observing
the constellation or symbols plots. But I think you'll be ok in using FFT once you
have the
AGC gain modes disabled.
Please let us know how you make out. Good luck!
Bill
-----Original Message-----
From: op25-dev <op25-dev-bounces(a)lists.osmocom.org> On Behalf Of op25(a)zellners.com
Sent: Sunday, September 6, 2020 9:29 AM
To: op25-dev(a)lists.osmocom.org
Subject: Re: [op25-dev] rx.py Airspy MASTER GAIN Setting option?????
Quoting wllmbecks(a)gmail.com:
The yellow highlighted text below in my rx.py command
line is an
example of how my R2 device was set to manual gain mode whereby the
device responds to user specified LNA, MIX,
and IF gain settings.
./rx.py --args "airspy=0,sensitivity=0,linearity=0,bias=0" -N
'LNA:15,MIX:15,IF:10' -S 2500000 -T trunk.tsv ………
Thanks... I think that may be the
magic,airspy=0,sensitivity=0,linearity=0,bias=0, as those names are
present in the other program, but hmm... I would expect since I nuked
them in that program it would persist? I guess not..
I will try this during some tests today... have to work on a more
mission critical option at first.
Thanks....
5 Sep
5 Sep
2:26 p.m.
I didn't pay particular attention to the original post but a (-q 2) would really be
unheard of with an Airspy device
unless it is way out of calibration. I suspect that the spike you're seeing in is not
a "real' signal.
Although it's hard to reproduce on demand, I have run into conditions where my FFT
plot displayed a spike at the
center of the spectrum that turned out to be false signal. Removing the antenna and
setting the LNA and Mixer gain
controls to zero made no difference in the amplitude of the spike at the center of the
spectrum.
As a suggestion, retest rx.py using (-q 0) as a starting point but add (-X) to let op25
try to resolve tuning errors to
see if you're actually getting a live signal, and check to see that op25 indicates
it's decoding trunk signaling blocks
and live traffic.
Raising and lowering LNA, MIXER, and IF gains should result in varying signal amplitude as
observed in the FFT plot
Typically, on my Airspy devices the IF gain maxes out at about a setting of 8-10 as far as
increasing signal amplitude
and whereby increasing IF gain only serves to raise the apparent noise floor and sometimes
introducing unwanted
IM products. But LNA and MIXER gains should play a very significant role in the signal
level as observed in the FFT plot
screen.
Bill
-----Original Message-----
From: op25-dev <op25-dev-bounces(a)lists.osmocom.org> On Behalf Of op25(a)zellners.com
Sent: Saturday, September 5, 2020 6:23 AM
To: op25-dev(a)lists.osmocom.org
Subject: Re: [op25-dev] rx.py Airspy MASTER GAIN Setting option?????
Quoting Graham Norbury <gnorbury(a)bondcar.com>om>:
I'm not aware of a master gain parameter. LNA,
MIX, IF are the three gain
controls. All take value between 0-15.
>
> ./rx.py --args 'airspy' -N 'IF:10,MIX:5,LNA:15' -S 2500000 -f
> 774.55625e6 -v 7 -T P25PC.tsv -q 2 -V -2 -U -x 2 2>> airspy.log
I reran my tests on this again, using -N 'IF:,MIX:,LNA:' like above with 0-15
values.
The spike for the CC, as a test, didn't budge at all, all 15, or anything in between,
no changes.
It is significantly lower to start -20 to -40db lower v. other programs and depending on
antenna.
Its almost like the gains are set to 0 or something and never change??? ? ? ? ?
Even using a duck direct to the Airspy with another program results in much higher signals
on its spectrum, and gains will adjust accordingly.
Changes will occur in another program with adjustments to all 3 (outside its faked single
slider mode, using just the REAL GAINS), gains shows changes in the signals and noise
floor.
In op25, not a bit of change at all in any thing. noise or signal.
Like these are not being sent? Or not taking affect?? ? ? 15 for all, combos of values,
even things like 50 for all three, no changes.
I am not sure what to even try at this point? Other than missing lib when it was
compiled??? I didn't have the airspy then or airspy pacakges installed when compiled..
does that change anything??? It seems to work regardless of that, it tunes, it will trunk,
voice etc., just the gains don't seem to do a thing at all. IF there was something
missing in this, I would expect it to fail to tune, audio etc..
Ideas?????
6 Sep
6 Sep
6:33 p.m.
Quoting wllmbecks(a)gmail.com:
I didn't pay particular attention to the original
post but a (-q 2)
would really be unheard of with an Airspy device
unless it is way out of calibration. I suspect that the spike
you're seeing in is not a "real' signal.
The -q 2 for PPM of 2, is based on another programs output of its auto ppm.
I will try with 0 as well. But with the 2 it was producing audio etc..
Although it's hard to reproduce on demand, I have run into
conditions where my FFT plot displayed a spike at the
center of the spectrum that turned out to be false signal.
Removing the antenna and setting the LNA and Mixer gain
controls to zero made no difference in the amplitude of the spike at
the center of the spectrum.
This is not a spur, or anything of the like. Disconnect the antenna,
its gone. I am not any sort of OP25 guru etc.... but lets just say
this ain't my first rodeo in RF.... :) :) ;)
As a suggestion, retest rx.py using (-q 0) as a
starting point but
add (-X) to let op25 try to resolve tuning errors to
see if you're actually getting a live signal, and check to see that
op25 indicates it's decoding trunk signaling blocks
and live traffic.
Op25 does already indicate its a live signal, just 20-40db down. I get
audio, TSBKS, using a -v10 I get the slew of decoded TSBK data, with
an occasional CRC error. Which is related to the low signal.
I am also not working from a guess on the frequencies of the
system(s). Lets just leave it at that I've got more knowledge about
what frequencies and towers these things are using that a certain
other site and the FCC does. :) ;) ;)
Raising and lowering LNA, MIXER, and IF gains should
result in
varying signal amplitude as observed in the FFT plot
Typically, on my Airspy devices the IF gain maxes out at about a
setting of 8-10 as far as increasing signal amplitude
and whereby increasing IF gain only serves to raise the apparent
noise floor and sometimes introducing unwanted
IM products. But LNA and MIXER gains should play a very significant
role in the signal level as observed in the FFT plot
I think in another setup I am about 10-12 for LNA, and 8-7 on the IF
and MIX as I recall. As I played to max signal and reduce the noise
floor. I'll have to find my note on it.. its not on this box.
I think the other post to disable what ever those modes are is the
key.. which when its reset, ie: powered off and moved to another box,
my OP25 setups is not that box since op25 is not Python3 compatible,
yet, and so I move it to the 18.04, with the ulitimate goal to
possibly move it to a Pi(s), which I was hoping to dump, but there is
a bug in another program to use them there. I am guessing the firmware
of the AS's resets it to use these modes??? Where as the other program
stores those settings and likely restores them when it sees the same
tuner... as it does this with RTL's...
We'll see what the tests do with the magic disable commands....
8:28 p.m.
A good tool is to take a look at your symbols and mixer plots to verify if the (-q 2) is
the
right prescription for your particular device. Start with (-q 0) and if you get
TSBK's then
let it run for five to ten minutes before checking the reported frequency error and then
make your corrections accordingly.
However, I have run the calibration utility on all of my Airspy devices using a GPSDO
as a stable and accurate frequency reference. In my case, the corrections added to
the rx.py command line were (-q 0.1) & (-o 30) that results in an average frequency
error of no more than 10-20 Hz as reported by op25.
Even though the R2's and Mini's are TCXO based, they are far from perfect and do
drift
the first five to ten minutes when starting up from cold. So, this has to be taken
into
consideration when running the calibration utility, or in making your PPM and offset
corrections in op25.
Bill
-----Original Message-----
From: op25-dev <op25-dev-bounces(a)lists.osmocom.org> On Behalf Of op25(a)zellners.com
Sent: Sunday, September 6, 2020 11:33 AM
To: op25-dev(a)lists.osmocom.org
Subject: Re: [op25-dev] rx.py Airspy MASTER GAIN Setting option?????
Quoting wllmbecks(a)gmail.com:
I didn't pay particular attention to the original
post but a (-q 2)
would really be unheard of with an Airspy device unless it is way out
of calibration. I suspect that the spike you're seeing in is not a
"real' signal.
The -q 2 for PPM of 2, is based on another programs output of its auto ppm.
I will try with 0 as well. But with the 2 it was producing audio etc..
Although it's hard to reproduce on demand, I have run into
conditions where my FFT plot displayed a spike at the
center of the spectrum that turned out to be false signal.
Removing the antenna and setting the LNA and Mixer gain
controls to zero made no difference in the amplitude of the spike at
the center of the spectrum.
This is not a spur, or anything of the like. Disconnect the antenna,
its gone. I am not any sort of OP25 guru etc.... but lets just say
this ain't my first rodeo in RF.... :) :) ;)
As a suggestion, retest rx.py using (-q 0) as a
starting point but
add (-X) to let op25 try to resolve tuning errors to
see if you're actually getting a live signal, and check to see that
op25 indicates it's decoding trunk signaling blocks
and live traffic.
Op25 does already indicate its a live signal, just 20-40db down. I get
audio, TSBKS, using a -v10 I get the slew of decoded TSBK data, with
an occasional CRC error. Which is related to the low signal.
I am also not working from a guess on the frequencies of the
system(s). Lets just leave it at that I've got more knowledge about
what frequencies and towers these things are using that a certain
other site and the FCC does. :) ;) ;)
Raising and lowering LNA, MIXER, and IF gains should
result in
varying signal amplitude as observed in the FFT plot
Typically, on my Airspy devices the IF gain maxes out at about a
setting of 8-10 as far as increasing signal amplitude
and whereby increasing IF gain only serves to raise the apparent
noise floor and sometimes introducing unwanted
IM products. But LNA and MIXER gains should play a very significant
role in the signal level as observed in the FFT plot
I think in another setup I am about 10-12 for LNA, and 8-7 on the IF
and MIX as I recall. As I played to max signal and reduce the noise
floor. I'll have to find my note on it.. its not on this box.
I think the other post to disable what ever those modes are is the
key.. which when its reset, ie: powered off and moved to another box,
my OP25 setups is not that box since op25 is not Python3 compatible,
yet, and so I move it to the 18.04, with the ulitimate goal to
possibly move it to a Pi(s), which I was hoping to dump, but there is
a bug in another program to use them there. I am guessing the firmware
of the AS's resets it to use these modes??? Where as the other program
stores those settings and likely restores them when it sees the same
tuner... as it does this with RTL's...
We'll see what the tests do with the magic disable commands....
8 Sep
8 Sep
5:05 p.m.
Quoting wllmbecks(a)gmail.com:
A good tool is to take a look at your symbols and
mixer plots to
verify if the (-q 2) is the
Thats why I use OP25 for the constellation etc. that other software
doesn't provide. More accurate to tune.
The 2 ppm is accurate as its confirmed with other programs. Which
start with a 0 and over time it is steady at 2ppm +- a little...
However, I have run the calibration utility on all of
my Airspy
devices using a GPSDO
What is the CLKIN expecting? I'd have to check to see that our GPS
simulcast controllers put out a similar or compatible signal... and I
might drag one to a site when I go to test with...
But the -q 2 setting is accurate as anything or more less, and nothing
decodes, nice tight constellation.
5:32 p.m.
You should be good to go if you have 10 MHz reference clock available. The Airspy's
accept anything from 10 MHz to 100 MHz external clock reference on the MCX connector.
Don't ask me how the internals figure this out or if any configuration is necessary to
specify
the source reference. I haven't tried this but will go back to my shop and connect
a 10 MHz
reference to an R2 to see what if any affect it has on op25 receiving a live p25 system.
Bill
-----Original Message-----
From: op25-dev <op25-dev-bounces(a)lists.osmocom.org> On Behalf Of op25(a)zellners.com
Sent: Tuesday, September 8, 2020 10:05 AM
To: op25-dev(a)lists.osmocom.org
Subject: Re: [op25-dev] rx.py Airspy MASTER GAIN Setting option?????
Quoting wllmbecks(a)gmail.com:
A good tool is to take a look at your symbols and
mixer plots to
verify if the (-q 2) is the
Thats why I use OP25 for the constellation etc. that other software
doesn't provide. More accurate to tune.
The 2 ppm is accurate as its confirmed with other programs. Which
start with a 0 and over time it is steady at 2ppm +- a little...
However, I have run the calibration utility on all of
my Airspy
devices using a GPSDO
What is the CLKIN expecting? I'd have to check to see that our GPS
simulcast controllers put out a similar or compatible signal... and I
might drag one to a site when I go to test with...
But the -q 2 setting is accurate as anything or more less, and nothing
decodes, nice tight constellation.
6:42 p.m.
Update....
I just completed running a few tests with one of my Airspy R2's operating with CLKIN
from an frequency agile GPSDO. The R2 works perfectly while the external reference
is set to 10 MHz but will not run at any other frequency.
The almost nonexistent Airspy literature states the R2 will operate with an external
clock
reference from 10 MHz to 100 MHz. However, from my tests is would seem that the user
must somehow configure the external reference frequency.
Therefore, if the specifications are accurate, then one can only conclude that the
default
external reference is set to 10 MHz where the R2 will initialize and operate when CLKIN
applied to the MCX input connector.
My test configuration with the external GPSDO reference tied to the R2 was tested
with op25 configured to MPSCS RFSS 5-15 (hex) and whereby rx.py was operating at defaults
having removed (-q x), (-o x) and (-d x) arguments from the command line with op25
reporting a frequency error of + 41 Hz on the control channel.
I am fairly confident that the MPSCS base stations (repeaters) at the above referenced
site are
all GTR8000's operating on external GPS referenced clock that if one were to make such
assumptions that the reported frequency error would be zero or very close to it but I
don't
know that I can accurately measure the site off air with my R2670B on external clock.
Further, I am not clear on just exactly how op25 measures frequency but want to recall
that
it takes into consideration symbol rate and spacing of each of the symbols in the
constellation?
Perhaps Max or Graham can shed some light on this aspect. Still in all, 41 Hz is close
enough for
government work that is stable and consistent as opposed to the R2 running on its own
TXCO.
Bill
-----Original Message-----
From: op25-dev <op25-dev-bounces(a)lists.osmocom.org> On Behalf Of op25(a)zellners.com
Sent: Tuesday, September 8, 2020 10:05 AM
To: op25-dev(a)lists.osmocom.org
Subject: Re: [op25-dev] rx.py Airspy MASTER GAIN Setting option?????
Quoting wllmbecks(a)gmail.com:
A good tool is to take a look at your symbols and
mixer plots to
verify if the (-q 2) is the
Thats why I use OP25 for the constellation etc. that other software
doesn't provide. More accurate to tune.
The 2 ppm is accurate as its confirmed with other programs. Which
start with a 0 and over time it is steady at 2ppm +- a little...
However, I have run the calibration utility on all of
my Airspy
devices using a GPSDO
What is the CLKIN expecting? I'd have to check to see that our GPS
simulcast controllers put out a similar or compatible signal... and I
might drag one to a site when I go to test with...
But the -q 2 setting is accurate as anything or more less, and nothing
decodes, nice tight constellation.
4 Sep
4 Sep
8:06 p.m.
Quoting Graham Norbury <gnorbury(a)bondcar.com>om>:
Airspy @ 15,15,15
RTL @ 47
I'll have to rerun the test to see.. I don't think real numbers were
put in as I was expecting to get an option for "MASTER"
I've since disabled that in the other software to use CORRECTLY as the
device provides gain versus some pseudo control which I don't know
what its doing..
I didn't get any movement at all in the signal on any of those gain
settings, but I also don't think I limited to 1-15 either..
I will retry since I've play'd with the other software to see what
settings seem to give the best SNR...
Of course, in the real world you'd tune the
gain(s) to find the best
SNR, which is typically the point just before the noise floor starts
rising appreciably.
Thats what is done, on the production unit. I admit to upping it a
little for rain fade, stray pine needles etc. for some fade margin.
Which does resolve those... I also use dedicated and professional LMR
antenna and cables, ie:LMR400, yagi at site etc.. I try to make up
with things at the antenna not at the other end.
I also use the constellation to get a good pattern and go from there.
With a good pattern there 99% of the time the rest will take of
itself. Mostly.
Now that I know the other is creating a fake setup, and what really
should be done I can test again.
Thanks.
8:10 p.m.
As Graham pointed out, there is no "Master" gain control built into the
interface specification
of Airspy devices. However, In addition to manual gain control, there are
sensitivity, and linearity modes
that apply AGC over the LNA and Mixer stages.
The "Master" gain control it seems is a feature in SDRTrunk whereby some
values are applied to the
LNA, Mixer, and IF gains settings in addition to allow the end user input
specific Tuner gain settings.
That said, there is no need to mimic overall RF amplitude values displayed
on op25 FFT plots.
The fundamental difference between typical RTL SDR devices and the Airspy
R2's and Mini's
is the much lower noise floor and the superior signal handling
characteristics of the Airspy.
At the end of the day it's all about Signal to Noise (S/N) performance of
any given radio receiver
that defines overall usable sensitivity.
Shown below are FFT plots captured from the same P25 system with an Airspy
R2 followed by
a NooElec SMArt. Observe the Airspy exhibits an average noise floor of
approximately -80 while
the RTL exhibits an average noise floor of approximately -63 to -64 that
clearly demonstrates
that the Airspy has a 16 to 17 dB advantage over the RTL device.
In addition to the lower noise performance, the signal handling in crowed
RF spectrums
of the Airspy is also a plus. I happen to live in a rural area where there
are few in-band 800 MHz
signals, but it should be noted that most RTL's suffer from self-induced
intermodulation interference
when operated in crowded RF spectrums.
Airspy R2 ./rx.py --args 'airspy' -S 2500000 -N 'LNA:15,MIX:15,IF:10'
NooElec RTL ./rx.py --args 'rtl' --gains 'lna:49'
The third FFT plot below does demonstrate the relatively poor IM performance
of an RTL SDR
captured from one of my remote instances of op25 tuned to a VHF P25 system
where there
are numerous in-band signals. In this case I am using a five element Yagi
antenna aimed at the
distant RFSS in combination with minimum LNA settings to mitigate as much of
the IM products
as are possible.
Signals shown in the plot below approximately -45 are IM products and are
not real in-band signals
when at times there are legitimate in-band signals that do produce IM
products that cause bit errors
to the desired P25 control or voice channels.
NooElec RTL ./rx.py --args 'rtl' --gains 'lna:49'
Bill
-----Original Message-----
From: op25-dev <op25-dev-bounces(a)lists.osmocom.org> On Behalf Of
op25(a)zellners.com
Sent: Friday, September 4, 2020 5:35 AM
To: op25-dev(a)lists.osmocom.org
Subject: Re: [op25-dev] rx.py Airspy MASTER GAIN Setting option?????
Quoting Graham Norbury < <mailto:gnorbury@bondcar.com>
gnorbury(a)bondcar.com>gt;:
I'm not aware of a master gain parameter. LNA,
MIX, IF are the three
gain
controls. All take value between 0-15.
Ummm...mmm...hmmmmmm...
SDRTrunk exposes:
4 CONTROLS and 3 options in a drop down.
A guess is these "modes" are some sort of custom setup? As you can set
CUSTOM MODE and you can then adjust IF,MIX,LNA separately... in SENSITIVITY
or LINEARITY MODES it has a "MASTER" slider which I will take it that if
there really are only 3 real gains must be a custom adjust to all 3 via that
slider???? Which it doesn't reflect in the GUI that its adjusting them....
but thats not really relevant here.
I am trying to match performance from an RTL to the Airspy, and the plot on
the spectrum is at least 20db down from the RTL (RTL Gain 49)..unless the
Airspys are significantly less sensitive which SDRT doesn't seem to show.
I get -20db power level with the RTL and and the airspy is at -40db...and
playing with those gains didn't seem to budge it... hmmm..
I'll give another whack tonight using only the 3 controls and see what I
get...
Thanks...
8:24 p.m.
On Fri, Sep 4, 2020 at 11:10 AM <wllmbecks(a)gmail.com> wrote:
As Graham pointed out, there is no “Master” gain
control built into the
interface specification
of Airspy devices. However, In addition to manual gain control, there are
sensitivity, and linearity modes
that apply AGC over the LNA and Mixer stages.
The “Master” gain control it seems is a feature in SDRTrunk whereby some
values are applied to the
LNA, Mixer, and IF gains settings in addition to allow the end user input
specific Tuner gain settings.
That said, there is no need to mimic overall RF amplitude values displayed
on op25 FFT plots.
The fundamental difference between typical RTL SDR devices and the Airspy
R2’s and Mini’s
is the much lower noise floor and the superior signal handling
characteristics of the Airspy.
At the end of the day it’s all about Signal to Noise (S/N) performance of
any given radio receiver
that defines overall usable sensitivity.
Shown below are FFT plots captured from the same P25 system with an Airspy
R2 followed by
a NooElec SMArt. Observe the Airspy exhibits an average noise floor of
approximately -80 while
the RTL exhibits an average noise floor of approximately -63 to -64 that
clearly demonstrates
that the Airspy has a 16 to 17 dB advantage over the RTL device.
Er, no.. it means that *after all of the gains have been applied*, the
noise floor measures differently. As you pointed out above, then apparently
immediately forgot, it's SNR that matters. Eyeballing your plots, it seems
like the SNR is similar - somewhere in the 35-40dB range (can't tell more
than that, given the resolution). Note that the vertical scale is not the
same between the two plots. Also, the RF frequency is not the same, so
that's probably not a fair comparison either.
~iain
In addition to the lower noise performance, the
signal handling in crowed
RF spectrums
of the Airspy is also a plus. I happen to live in a rural area where
there are few in-band 800 MHz
signals, but it should be noted that most RTL’s suffer from self-induced
intermodulation interference
when operated in crowded RF spectrums.
*Airspy R2 ./rx.py --args 'airspy' -S 2500000 -N 'LNA:15,MIX:15,IF:10'*
*NooElec RTL** ./rx.py --args 'rtl' --gains 'lna:49'*
The third FFT plot below does demonstrate the relatively poor IM
performance of an RTL SDR
captured from one of my remote instances of op25 tuned to a VHF P25 system
where there
are numerous in-band signals. In this case I am using a five element
Yagi antenna aimed at the
distant RFSS in combination with minimum LNA settings to mitigate as much
of the IM products
as are possible.
Signals shown in the plot below approximately -45 are IM products and are
not real in-band signals
when at times there are legitimate in-band signals that do produce IM
products that cause bit errors
to the desired P25 control or voice channels.
*NooElec RTL** ./rx.py --args 'rtl' --gains 'lna:49'*
Bill
-----Original Message-----
From: op25-dev <op25-dev-bounces(a)lists.osmocom.org> On Behalf Of
op25(a)zellners.com
Sent: Friday, September 4, 2020 5:35 AM
To: op25-dev(a)lists.osmocom.org
Subject: Re: [op25-dev] rx.py Airspy MASTER GAIN Setting option?????
Quoting Graham Norbury <gnorbury(a)bondcar.com>om>:
I'm not aware of a master gain parameter.
LNA, MIX, IF are the three
gain
controls. All take value between 0-15.
Ummm...mmm...hmmmmmm...
SDRTrunk exposes:
4 CONTROLS and 3 options in a drop down.
A guess is these "modes" are some sort of custom setup? As you can set
CUSTOM MODE and you can then adjust IF,MIX,LNA separately... in SENSITIVITY
or LINEARITY MODES it has a "MASTER" slider which I will take it that if
there really are only 3 real gains must be a custom adjust to all 3 via
that slider???? Which it doesn't reflect in the GUI that its adjusting
them.... but thats not really relevant here.
I am trying to match performance from an RTL to the Airspy, and the plot
on the spectrum is at least 20db down from the RTL (RTL Gain 49)..unless
the Airspys are significantly less sensitive which SDRT doesn't seem to
show.
I get -20db power level with the RTL and and the airspy is at -40db...and
playing with those gains didn't seem to budge it... hmmm..
I'll give another whack tonight using only the 3 controls and see what I
get...
Thanks...
1336
days inactive
1340
days old
17 comments
4 participants
participants (4)
-
Graham Norbury -
iain macdonnell - N6ML -
op25＠zellners.com -
wllmbecks＠gmail.com