# Re: TX characterisation of USRPN210 with SBX daughterboard **URL:** \ **Category:** GNU Radio\ **Created:** [March 24, 2014, 11:00pm UTC](https://www.ruby-forum.com/t/re-tx-characterisation-of-usrpn210-with-sbx-daughterboard/240019 "2014-03-24T23:00:53Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![musicdenotation](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/ea666f/32.png) [@musicdenotation](https://www.ruby-forum.com/u/musicdenotation)\ **Post date:** [March 24, 2014, 11:00pm UTC](https://www.ruby-forum.com/t/re-tx-characterisation-of-usrpn210-with-sbx-daughterboard/240019/1 "2014-03-24T23:00:53Z")
Hi Ron Sorry about that. Please find attached the modified graph. The two curves seems more consistent in this graph. I am assuming the DAC should have reached saturation at Ampl =1. However my reading don’t seem to depict that so well. Would it have been better to started at such lower values of Amplitude? I understand for a SBX board, the Tx’d o/p power range is +16 -20 dbm ( 1.5 to 2.2 V) with a 32 dB gain control range, which I understand that I can vary the Tx’d power from -16 dBm to +16 dBm (0.035 V ~ 1.5 V). Is my understanding correct?. So should I vary my ampltude from 0.035 V untl 1.5 V? is that within the usrpN210’s working levels? Thanks On Mon, Mar 24, 2014 at 3:48 PM, Ron E. [via GnuRadio] \< removed\_email\_address@domain.invalid\> wrote: > > SBX board. > > Amplitude change 921MHz 2.456GHz > > converge at a higher ampl and o/p power. [http://gnuradio.4.n7.nabble.com/TX-characterisation-of-USRPN210-with-SBX-daughterboard-tp47157p47165.html](http://gnuradio.4.n7.nabble.com/TX-characterisation-of-USRPN210-with-SBX-daughterboard-tp47157p47165.html) > To unsubscribe from TX characterisation of USRPN210 with SBX > daughterboard, click > here[http://gnuradio.4.n7.nabble.com/template/NamlServlet.jtp?macro=unsubscribe\_by\_code&node=47157&code=Z3JhbWFzdWJAdnQuZWR1fDQ3MTU3fDEzNjkyOTkyNzY=](http://gnuradio.4.n7.nabble.com/template/NamlServlet.jtp?macro=unsubscribe_by_code&node=47157&code=Z3JhbWFzdWJAdnQuZWR1fDQ3MTU3fDEzNjkyOTkyNzY=) > . NAML[http://gnuradio.4.n7.nabble.com/template/NamlServlet.jtp?macro=macro\_viewer&id=instant\_html!nabble%3Aemail.naml&base=nabble.naml.namespaces.BasicNamespace-nabble.view.web.template.NabbleNamespace-nabble.view.web.template.NodeNamespace&breadcrumbs=notify\_subscribers!nabble%3Aemail.naml-instant\_emails!nabble%3Aemail.naml-send\_instant\_email!nabble%3Aemail.naml](http://gnuradio.4.n7.nabble.com/template/NamlServlet.jtp?macro=macro_viewer&id=instant_html%21nabble%3Aemail.naml&base=nabble.naml.namespaces.BasicNamespace-nabble.view.web.template.NabbleNamespace-nabble.view.web.template.NodeNamespace&breadcrumbs=notify_subscribers%21nabble%3Aemail.naml-instant_emails%21nabble%3Aemail.naml-send_instant_email%21nabble%3Aemail.naml) > Tx\_waveforms\_plot1.PNG (32K) [http://gnuradio.4.n7.nabble.com/attachment/47168/0/Tx\_waveforms\_plot1.PNG](http://gnuradio.4.n7.nabble.com/attachment/47168/0/Tx_waveforms_plot1.PNG) ---
**Author:** ![Gayathri\_Ramasubram](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/g/9fc29f/32.png) [@Gayathri\_Ramasubram](https://www.ruby-forum.com/u/Gayathri_Ramasubram)\ **Post date:** [March 25, 2014, 12:04pm UTC](https://www.ruby-forum.com/t/re-tx-characterisation-of-usrpn210-with-sbx-daughterboard/240019/2 "2014-03-25T12:04:41Z")
I took a look at the SBX schematic. The final output uses a Mini-Circuits PHA-1+ MMIC amplifier that’s rated at +22 dBm output power at 1 dB compression. It would seem that the gain distribution of the SBX is arranged so that the PHA-1+ cannot be overdriven, even at DAC full-scale and 0 dB attenuation. That is, you cannot saturate the SBX. So your measurements are showing that the SBX is quite linear over it’s operating range. BTW, I’m not really familiar with the USRP (I’m a bladeRF user), but the amplitude value in tx\_waveforms is most likely just a relative amplitude (with 1 equal to DAC full-scale), and not an actual voltage. Ron ---
**Author:** ![Gayathri\_Ramasubram](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/g/9fc29f/32.png) [@Gayathri\_Ramasubram](https://www.ruby-forum.com/u/Gayathri_Ramasubram)\ **Post date:** [March 25, 2014, 12:35pm UTC](https://www.ruby-forum.com/t/re-tx-characterisation-of-usrpn210-with-sbx-daughterboard/240019/3 "2014-03-25T12:35:42Z")
Ron, thanks for the input! On 03/25/2014 12:02 PM, Ron E. wrote: > quite linear over it’s operating range. > > BTW, I’m not really familiar with the USRP (I’m a bladeRF > user), but the amplitude value in tx\_waveforms is most > likely just a relative amplitude (with 1 equal to DAC > full-scale), and not an actual voltage. That is correct. If you were using GNU Radio, and connected that to a USRP, this would be amplitude of the digital signal going into the USRP sink. Martin