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View all threadsb210 tx power
Hello!
There were a few topics about b210 TX power. And mentioned value about 50mW. But...We got a very small output power on the different frequencies.
We using an agilent spectrum analizer for power measurement.
GNUradio DBPSK flowgraph running on the host PC, with gain power control via UHD Sink block, carrier frequency 433MHz, sample rate 500k. On max gain 89dB we see the spectrum with average power -3 dBm.
B210 and analizer connected via cable with loss about 0.5 dB. Input impedance of analizer 50 Ohm.
To check the analizer we filed it with almost the same signal from generator with power 10 dBm and the analizer measured 9.5 dBm (0.5dB loss in cabel).
The message includes the screenshot in case of Tx_gain=75dB.
Maybe someone spent such measurements and got something like that? What measurement tools u use? What kinds of signal u use? What power value u get?
Thanks in advance.
Dmitry.
First of all you need to know that your signal occupies a large bandwidth,
so the energy is spread and does not reach the 20dBm line on your analyzer.
To see the real peak power the easiest way is to transmit an unmodulated
carrier and watch this with the analyzer.
Then of course the PA does not have identical gain over the whole frequency
range, you can get an idea by having a look at the data sheet of the MMIC.
So it will drop with higher frequency. Without having measured it, I expect
a remarkable drop when going above 1 GHz. My quick comparison with OpenBTS
using 900 and 1800 MHz for GSM transmissions seems to prove this.
Ralph.
-----Original Message-----
From: USRP-users [mailto:usrp-users-bounces@lists.ettus.com] On Behalf Of
Dmitry via USRP-users
Sent: Thursday, October 30, 2014 7:27 AM
To: usrp-users@lists.ettus.com
Subject: [USRP-users] b210 tx power
Hello!
There were a few topics about b210 TX power. And mentioned value about
50mW. But...We got a very small output power on the different frequencies.
We using an agilent spectrum analizer for power measurement.
GNUradio DBPSK flowgraph running on the host PC, with gain power control
via UHD Sink block, carrier frequency 433MHz, sample rate 500k. On max
gain
89dB we see the spectrum with average power -3 dBm.
B210 and analizer connected via cable with loss about 0.5 dB. Input
impedance of analizer 50 Ohm.
To check the analizer we filed it with almost the same signal from
generator
with power 10 dBm and the analizer measured 9.5 dBm (0.5dB loss in cabel).
The message includes the screenshot in case of Tx_gain=75dB.
Maybe someone spent such measurements and got something like that?
What measurement tools u use? What kinds of signal u use? What power
value u get?
Thanks in advance.
Dmitry.
Hi Ralph, Hi Dmitry,
I don't have measurements for the b210, but the ones for the b200 tx
(which should be pretty identical to the b210) indicate that the
variation of TX power between 100MHz and 2GHz is about 6dB max (for the
30dB gain case). So, depending on what you consider to be remarkable,
you might call this a remarkable drop; however, I don't think TX power
is that critical for GSM; what are the operational differences you see
at 1.8GHz?
Regarding Dmitry's Measurements:
DBPSK might not be the measurement tool of choice, here, as sending
modulated data with (I'm assuming two samples per symbol, no further
filtering), 250k symbols/s cannot work well if your analyzer measures
the energy per frequency spot for only 20µs at best.
As Ralph said, you should go for something easier to recognize sprectrally.
UHD comes with a handy example, tx_waveforms, which you can use like:
tx_waveforms --rate 0.5e6 --gain 75 --wave-type SINE --wave-freq 1e3
--freq 433e6
If you're already using GNU Radio, you could also generate noise (using
the noise source) and feed that directly into your USRP sink, and that
should give you something broad.
Another thing that happened to me a few times and made me question my
sanity was connecting to the wrong port of my USRP (that was with N210s,
though).
Greetings,
Marcus
On 30.10.2014 08:19, Ralph A. Schmid, dk5ras via USRP-users wrote:
First of all you need to know that your signal occupies a large bandwidth,
so the energy is spread and does not reach the 20dBm line on your analyzer.
To see the real peak power the easiest way is to transmit an unmodulated
carrier and watch this with the analyzer.
Then of course the PA does not have identical gain over the whole frequency
range, you can get an idea by having a look at the data sheet of the MMIC.
So it will drop with higher frequency. Without having measured it, I expect
a remarkable drop when going above 1 GHz. My quick comparison with OpenBTS
using 900 and 1800 MHz for GSM transmissions seems to prove this.
Ralph.
-----Original Message-----
From: USRP-users [mailto:usrp-users-bounces@lists.ettus.com] On Behalf Of
Dmitry via USRP-users
Sent: Thursday, October 30, 2014 7:27 AM
To: usrp-users@lists.ettus.com
Subject: [USRP-users] b210 tx power
Hello!
There were a few topics about b210 TX power. And mentioned value about
50mW. But...We got a very small output power on the different frequencies.
We using an agilent spectrum analizer for power measurement.
GNUradio DBPSK flowgraph running on the host PC, with gain power control
via UHD Sink block, carrier frequency 433MHz, sample rate 500k. On max
gain
89dB we see the spectrum with average power -3 dBm.
B210 and analizer connected via cable with loss about 0.5 dB. Input
impedance of analizer 50 Ohm.
To check the analizer we filed it with almost the same signal from
generator
with power 10 dBm and the analizer measured 9.5 dBm (0.5dB loss in cabel).
The message includes the screenshot in case of Tx_gain=75dB.
Maybe someone spent such measurements and got something like that?
What measurement tools u use? What kinds of signal u use? What power
value u get?
Thanks in advance.
Dmitry.
USRP-users mailing list
USRP-users@lists.ettus.com
http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
Hello Dmitry,
what you see from your analyzer is the power at a particular frequency
(for example marker 1 is at 432.974 MHz) over a bandwidth equal to your
resolution bandwidth (18 kHz) and that value is -8dBm.
But your signal is much wider than 18 kHz (it seems about 360 kHz) so
you are not measuring the full power transmitted by the radio but only a
tiny fraction of it.
Please check if your analyzer has a channel power meter option such that
you can calculate the integral of the power over the full signal
bandwidth or make your resolution bandwidth wider such that you account
for all the power transmitted.
From what I see, I would say that your output power is close to few dBm
(approximating your signal to have a flat power output over 360 kHz).
Furthermore, what is the absolute accuracy in power of your analyzer?
Generally it's quite bad on analyzers that do not have a dedicated power
meter (sometimes up to 1-2 dB).
Regards,
Stefano
On 10/30/2014 07:27, Dmitry via USRP-users wrote:
Hello!
There were a few topics about b210 TX power. And mentioned value about 50mW. But...We got a very small output power on the different frequencies.
We using an agilent spectrum analizer for power measurement.
GNUradio DBPSK flowgraph running on the host PC, with gain power control via UHD Sink block, carrier frequency 433MHz, sample rate 500k. On max gain 89dB we see the spectrum with average power -3 dBm.
B210 and analizer connected via cable with loss about 0.5 dB. Input impedance of analizer 50 Ohm.
To check the analizer we filed it with almost the same signal from generator with power 10 dBm and the analizer measured 9.5 dBm (0.5dB loss in cabel).
The message includes the screenshot in case of Tx_gain=75dB.
Maybe someone spent such measurements and got something like that? What measurement tools u use? What kinds of signal u use? What power value u get?
Thanks in advance.
Dmitry.
USRP-users mailing list
USRP-users@lists.ettus.com
http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
Hi,
I don't have measurements for the b210, but the ones for the b200 tx
(which
should be pretty identical to the b210) indicate that the variation of TX
power
between 100MHz and 2GHz is about 6dB max (for the 30dB gain case). So,
depending on what you consider to be remarkable, you might call this a
My estimation was near 10dB, but OK, 6dB are possible, too.
remarkable drop; however, I don't think TX power is that critical for GSM;
what are the operational differences you see at 1.8GHz?
At least the operational range drops significantly, even on line of sight.
The Rangenetworks SDR1 delivers at 1.8GHz about the same downlink range like
the B210 at 900 MHz, while the B210 at 1.8GHz only has half or a third of
the SDR1 range. Of course with identical antennae, identical location,
identical phone.
This discussion makes me curious, I will measure it with my old HP and tell
about the results.
Another thing that happened to me a few times and made me question my
sanity was connecting to the wrong port of my USRP (that was with N210s,
though).
Oh, yes, you are mentioning here a not so bright spot of my experiments,
when coverage ended at the door of my office. WTF?! Took me a while to
figure out. This resulted in putting red caps onto the usually unused ports
of my B210 :-)
Greetings,
Marcus
Ralph.
On 10/30/2014 07:21 AM, Ralph A. Schmid, dk5ras via USRP-users wrote:
Hi,
I don't have measurements for the b210, but the ones for the b200 tx
(which
should be pretty identical to the b210) indicate that the variation of TX
power
between 100MHz and 2GHz is about 6dB max (for the 30dB gain case). So,
depending on what you consider to be remarkable, you might call this a
My estimation was near 10dB, but OK, 6dB are possible, too.
remarkable drop; however, I don't think TX power is that critical for GSM;
what are the operational differences you see at 1.8GHz?
At least the operational range drops significantly, even on line of sight.
The Rangenetworks SDR1 delivers at 1.8GHz about the same downlink range like
the B210 at 900 MHz, while the B210 at 1.8GHz only has half or a third of
the SDR1 range. Of course with identical antennae, identical location,
identical phone.
This discussion makes me curious, I will measure it with my old HP and tell
about the results.
Another thing that happened to me a few times and made me question my
sanity was connecting to the wrong port of my USRP (that was with N210s,
though).
Oh, yes, you are mentioning here a not so bright spot of my experiments,
when coverage ended at the door of my office. WTF?! Took me a while to
figure out. This resulted in putting red caps onto the usually unused ports
of my B210 :-)
Greetings,
Marcus
Ralph.
You can't reliably use "communication range experiments" to measure power.
Also, don't forget, that the path-loss laws scale with wavelength.
You can easily see this with on-line path-loss caclulators.
--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org