<div dir="ltr"><div><div><div>Hello Marcus Müller,<br><br></div>Thank you, I will give it a shot.<br><br></div>Regards,<br></div>Kyeong Su Shin<br></div><div class="gmail_extra"><br><div class="gmail_quote">On Thu, Jul 27, 2017 at 6:34 AM, Marcus Müller 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">
    <p>Dear Kyeong Su Shin,</p>
    <p>so, when things already get "seriously overloaded" at 15dB gain,
      and you're running at 0 dB, I think the likeliest explanation is
      that at 0 dB, you're already seeing the effects of overloading.
      Try with something like 40 dB attenuation between antenna and LNA.</p>
    <p>Best regards,</p>
    <p>Marcus<br>
    </p><div><div class="h5">
    <br>
    <div class="m_-8907372910987454456moz-cite-prefix">On 07/27/2017 09:41 AM, Kyeong Su Shin
      via USRP-users wrote:<br>
    </div>
    <blockquote type="cite">
      <div dir="ltr">Hello Marcus Müller,
        <div><br>
        </div>
        <div>I have no control to the TX power, as it is attached to an
          outdoor discone antenna (sorry, I forgot to mention that). I
          am cross-checking the measured spectrum against an Aglient
          spectrum analyzer. I am also using 0dB RX gain now, although
          maybe I can go and attach more attenuators to achieve lower
          gain levels.</div>
        <div><br>
        </div>
        <div>I tried increasing the RX gain (instead of decreasing it),
          and the relationship was apparently linearly dependent. (5dB
          increase in gain -> approx. 5dB increase in the power level
          in dBFS, 10dB increase in gain -> approx. 11dB increase in
          the power level in dBFS). The LNA got seriously overloaded
          when I tried 15dB RX gain (noise increase). The strength of
          the spurious signal was quickly varying, so I could have had
          mismeasured it, though. <br>
        </div>
        <div><br>
        </div>
        <div>Attached is the PSD estimates collected using a Agilent SA
          (somewhat coarse version). <br>
        </div>
        <div><br>
        </div>
        <div>Regards,</div>
        <div>Kyeong Su Shin</div>
        <div class="gmail_extra"><br>
          <div class="gmail_quote">On Wed, Jul 26, 2017 at 1:07 PM,
            Marcus Müller 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 text="#000000" bgcolor="#FFFFFF">
                <p>Hello Kyeong Su Shin,</p>
                <p>what's the RF power reaching the USRP? Does this get
                  better when you reduce the RX gain or the TX power?</p>
                <p>Best regards,</p>
                <p>Marcus<br>
                </p>
                <div>
                  <div class="m_-8907372910987454456m_6730431007461864832m_-3678133588834184649h5">
                    <br>
                    <div class="m_-8907372910987454456m_6730431007461864832m_-3678133588834184649m_1092481168663392528moz-cite-prefix">On
                      26.07.2017 16:52, Kyeong Su Shin via USRP-users
                      wrote:<br>
                    </div>
                  </div>
                </div>
                <blockquote type="cite">
                  <div>
                    <div class="m_-8907372910987454456m_6730431007461864832m_-3678133588834184649h5">
                      <div dir="ltr">Hello,
                        <div><br>
                        </div>
                        <div>I observe a spurious signal in the PSD
                          estimates that are obtained using a USRP,
                          which I cannot identify the cause. Could
                          someone help me identifying the cause of this?
                          <br>
                          <br>
                        </div>
                        <div>Plots are shown below.<br>
                        </div>
                        <div><br>
                          <div><u>Hardware</u>:<br>
                          </div>
                          <div>-USRP N200 r4 + UBX-40 v1<br>
                          </div>
                          -Agilent FieldFox SA, as the reference.<br>
                          <br>
                          <div><u>Software</u>:<br>
                          </div>
                          <div>-Windows Server 2012 <br>
                          </div>
                          <div>-UHD 3.9.3<br>
                          </div>
                          <div>-GNURadio 3.7.10.1<br>
                            <div><br>
                              ..and also on a UHD-based (non-GNU Radio)
                              spectrum scanner script that I am working
                              on.<br>
                            </div>
                            <div><br>
                            </div>
                          </div>
                          <div><u>Setting</u>:<br>
                          </div>
                          <div>Gain : 0<br>
                          </div>
                          <div>lo offset : 0<br>
                          </div>
                          <div>Samp rate : 25MS/s (100e6/4)<br>
                          </div>
                          Antenna: RX2<br>
                          <br>
                        </div>
                        <div><u>The Spurious Signal:</u><br>
                        </div>
                        <div><br>
                        </div>
                        <div>@ fc = 641.25 MHz (reproducible at 642 /
                          641 MHz)<br>
                        </div>
                        <div><img src="cid:part2.BB5D4C52.7AC6A7AD@ettus.com" width="532" height="399"><br>
                          ​<br>
                        </div>
                        <div>Goes away @ fc = 630MHz.<br>
                        </div>
                        <div><img src="cid:part3.30B8D0D2.036541B3@ettus.com" width="532" height="399"><br>
                          ​<br>
                        </div>
                        <div><u>+- 25MHz</u>:<u> <br>
                            <br>
                          </u>No, I don't see any signal that could get
                          aliased; I believe this is not due to the
                          aliasing from the DDC.<u><br>
                            <br>
                          </u></div>
                        <div><img src="cid:part4.32CC0FB1.F2AE046C@ettus.com" width="532" height="399"><br>
                          <img src="cid:part5.81CE7EB7.CF8D836D@ettus.com" width="532" height="399"><br>
                          ​<br>
                        </div>
                        <div><u>1/2 fc (315MHz):</u> Clean (no signal
                          observed).<br>
                          <br>
                          <img src="cid:part6.7DF4CBBD.CAF9ACBA@ettus.com" width="532" height="399"><br>
                          ​<br>
                        </div>
                        <div><br>
                          <div>Regards,</div>
                          <div>Kyeong Su Shin</div>
                        </div>
                      </div>
                      <br>
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                      <br>
                    </div>
                  </div>
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