[USRP-users] b210 tx power

Ralph A. Schmid, dk5ras ralph at schmid.xxx
Thu Oct 30 03:19:34 EDT 2014


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 at lists.ettus.com] On Behalf Of
> Dmitry via USRP-users
> Sent: Thursday, October 30, 2014 7:27 AM
> To: usrp-users at 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.





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