<div dir="ltr"><span style="font-size:12.8px">Dear Marcus D. Leech:</span><div style="font-size:12.8px"><br></div><div style="font-size:12.8px">Thank you very much! I will think about this.</div><div style="font-size:12.8px"><br></div><div style="font-size:12.8px">Regards,</div><div style="font-size:12.8px">Kyeong Su Shin</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Nov 14, 2017 at 7:37 PM, Marcus D. Leech <span dir="ltr"><<a href="mailto:mleech@ripnet.com" target="_blank">mleech@ripnet.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
  
    
  
  <div bgcolor="#FFFFFF" text="#000000"><span class="">
    <div class="m_-1392143735149349282moz-cite-prefix">On 11/14/2017 10:31 PM, Kyeong Su Shin
      wrote:<br>
    </div>
    <blockquote type="cite">
      <div dir="ltr">Dear Marcus D. Leech:
        <div><br>
        </div>
        <div>Thank you for the reply. </div>
        <div><br>
        </div>
        <div>Is the only advantage of the TwinRX the pre-selector filter
          bank? Or, can the superheterodyne design of the radio also
          affect the data quality in some ways?</div>
      </div>
    </blockquote></span>
    A Low-IF superhet design has some advantages, but the UBX has the
    same overall architecture.  With a Zero-iF design, mixer balance is
    extremely<br>
      important, and not always easy to achieve "perfectly".  In the
    end, it's a matter of where your mixer images end up.<span class=""><br>
    <blockquote type="cite">
      <div dir="ltr">
        <div><br>
        </div>
        <div>We do turn down the gain to get optimal results. (The
          'noise figure' that I mentioned was the noise figure that is
          observed by us, after such adjustments). We will definitely
          try adding filters.</div>
      </div>
    </blockquote></span>
    Keep in mind that filters "out front" necessarily add to the noise
    figure of your receiver, since they aren't loss-free.  RF system
    design is all about<br>
      trade-offs.<div><div class="h5"><br>
    <br>
    <br>
    <blockquote type="cite">
      <div dir="ltr">
        <div><br>
        </div>
        <div>Regards,</div>
        <div>Kyeong Su Shin</div>
      </div>
      <div class="gmail_extra"><br>
        <div class="gmail_quote">On Tue, Nov 14, 2017 at 7:12 PM, Marcus
          D. Leech via USRP-users <span dir="ltr"><<a href="mailto:usrp-users@lists.ettus.com" target="_blank">usrp-users@lists.ettus.com</a>></span>
          wrote:<br>
          <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
            <div bgcolor="#FFFFFF" text="#000000">
              <div>
                <div class="m_-1392143735149349282h5">
                  <div class="m_-1392143735149349282m_3387366616527522229moz-cite-prefix">On
                    11/14/2017 10:00 PM, Kyeong Su Shin via USRP-users
                    wrote:<br>
                  </div>
                </div>
              </div>
              <blockquote type="cite">
                <div>
                  <div class="m_-1392143735149349282h5">
                    <div dir="ltr">
                      <div>
                        <div>Hello Everyone:<br>
                        </div>
                        <div><br>
                        </div>
                        <div>We are using USRPs for spectrum sensing (on
                          pretty much any frequencies). Before asking my
                          faculty to order a TwinRX daughterboard,
                          however, I would like to see if there are any
                          ways to improve the sensitivity of the
                          hardware that we currently own
                          (UBX/SBX/CBX/WBX). <br>
                        </div>
                        <div><br>
                        </div>
                        <div>Our USRP + UBX configuration works well,
                          except that we cannot really increase the gain
                          level much without putting the RF frontend
                          into the nonlinear region. Because of this,
                          the noise figure of our data is about ~30dB in
                          the worst case. I believe that the main
                          problem is that we are using a wideband
                          outdoor discone antenna for this - dumping
                          quite a lot of RF energy to the RF frontend. <br>
                        </div>
                        <div><br>
                        </div>
                        <div>In this case, what could I try to improve
                          the sensitivity of the radio? I think one
                          option could be adding additional filters to
                          the chain (when we know that we are only
                          looking at a certain frequencies), but I
                          wonder if there are anything else that I can
                          try. <br>
                        </div>
                        <div><br>
                        </div>
                        <div>Also, I wonder what differences we can
                          expect if we switch our daughterboard to a
                          TwinRX. Would it be worth it? What noise
                          figures did people experience when a wideband
                          outdoor antenna was connected to the board?<br>
                        </div>
                        <div><br>
                        </div>
                        Regards,<br>
                      </div>
                      Kyeong Su Shin<br>
                    </div>
                    <br>
                    <fieldset class="m_-1392143735149349282m_3387366616527522229mimeAttachmentHeader"></fieldset>
                    <br>
                  </div>
                </div>
                <pre>______________________________<wbr>_________________
USRP-users mailing list
<a class="m_-1392143735149349282m_3387366616527522229moz-txt-link-abbreviated" href="mailto:USRP-users@lists.ettus.com" target="_blank">USRP-users@lists.ettus.com</a>
<a class="m_-1392143735149349282m_3387366616527522229moz-txt-link-freetext" href="http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com" target="_blank">http://lists.ettus.com/mailman<wbr>/listinfo/usrp-users_lists.<wbr>ettus.com</a>
</pre>
              </blockquote>
              In the case of overload, the noise-figure is NOT the
              dominating factor in determining system sensitivity.<br>
              <br>
              If you are "sensing" across a limited band, then a filter
              that covers that band, and that band only, will definitely
              help keep the very first gain stages,<br>
                which are "wide open" from going into overload.<br>
              <br>
              The TwinRX has some significant advantage here, since it
              has pre-selector filters, but those filters may or may not
              have band edges that correspond<br>
                adequately to the band that your are "sensing".<br>
              <br>
              Basically, there's a "tension" in small-signal RF
              amplifiers.   They can either have very high dynamic
              range, or they can have very-low noise figure.<br>
                That general axiom still applies, although things are
              getting somewhat better in this regard.    But taking the
              output of an outdoor disc-cone antenna<br>
                in a normal urban environment is pretty-much begging for
              non-linearity.    You might try turning *down* the gain.<br>
              <br>
              <br>
              <br>
              <br>
            </div>
            <br>
            ______________________________<wbr>_________________<br>
            USRP-users mailing list<br>
            <a href="mailto:USRP-users@lists.ettus.com" target="_blank">USRP-users@lists.ettus.com</a><br>
            <a href="http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com" rel="noreferrer" target="_blank">http://lists.ettus.com/mailman<wbr>/listinfo/usrp-users_lists.<wbr>ettus.com</a><br>
            <br>
          </blockquote>
        </div>
        <br>
      </div>
    </blockquote>
    <br>
  </div></div></div>

</blockquote></div><br></div>