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    On 12/02/2014 10:06 AM, khalid.el-darymli wrote:
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cite="mid:CACdmG=xo5LGUgM_XW5BHuSpSme667oYe0sh3mo9xpv9w+bdT6w@mail.gmail.com"
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            <div>Hi Marcus,<br>
              <br>
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            Is there a temperature sensor on-board the N200 unit? If
            not, does it support installing any such sensor?<br>
            <br>
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          Thanks.<br>
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    No, and no.<br>
    <br>
    But there are a tonne of USB-based temperature sensors out there. 
    Google is your friend, etc.<br>
    <br>
    <br>
    <br>
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cite="mid:CACdmG=xo5LGUgM_XW5BHuSpSme667oYe0sh3mo9xpv9w+bdT6w@mail.gmail.com"
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        Best regards,<br>
        Khalid<br>
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                    <div class="gmail_quote">On Fri, Nov 28, 2014 at
                      5:44 PM, Marcus D. Leech <span dir="ltr"><<a
                          moz-do-not-send="true"
                          href="mailto:mleech@ripnet.com"
                          target="_blank">mleech@ripnet.com</a>></span>
                      wrote:<br>
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                            class=""> On 11/28/2014 03:41 PM,
                            khalid.el-darymli wrote:
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                                <div><span style="color: rgb(0, 0,
                                    255);">Back to my original question,
                                    what should I do to correct for
                                    this?<br>
                                    <br>
                                  </span></div>
                                <div><span style="color: rgb(0, 0,
                                    255);">Thanks in advance.<br>
                                    <br>
                                  </span></div>
                                <div><span style="color: rgb(0, 0,
                                    255);">Best,<br>
                                    Khalid</span><br>
                                  <br>
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                          </span> Khalid:<br>
                          <br>
                          Thanks very much for the very-extensive data. 
                          My main concern, as one of the Ettus support
                          team, was that there was something wrong with<br>
                            the hardware, but the magnitude of both the
                          apparent phase and magnitude drift is entirely
                          consistent with analog-hardware temperature<br>
                            effects, unrelated to clock stability, etc.<br>
                          <br>
                          Coax cables, for example, will change their
                          loss characteristics and *effective length*
                          with temperature, so with precise hardware
                          like USRPs, it's<br>
                            easy to see these effects.<br>
                          <br>
                          FMCW radar isn't my area of expertise, so
                          hopefully others can comment on RX-processing
                          strategies to deal with this, as it *must*
                          also be a problem<br>
                            with non-SDR FMCW radar implementations.<span
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                                <div class="gmail_extra"><br>
                                  <div class="gmail_quote">On Fri, Nov
                                    28, 2014 at 12:08 PM, <span
                                      dir="ltr"><<a
                                        moz-do-not-send="true"
                                        href="mailto:mleech@ripnet.com"
                                        target="_blank">mleech@ripnet.com</a>></span>
                                    wrote:<br>
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                                        <p>What is the magnitude of the
                                          frequency drift?</p>
                                        <p>What is the magnitude of the
                                          gain drift?</p>
                                        <p>What are you measuring
                                          backscatter *from*?</p>
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                                            <p> </p>
                                            <p> </p>
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                                            <p>On 2014-11-28 10:14,
                                              khalid.el-darymli via
                                              USRP-users wrote:</p>
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                                                  <div>Hi,<br>
                                                    <br>
                                                  </div>
                                                  Given a set of synced
                                                  <i>(i.e., using
                                                    external GPS
                                                    REF/PPS)</i>,
                                                  time-commanded and
                                                  calibrated <i>(i.e.,
                                                    through compensating
                                                    for the phase/mag
                                                    offset between
                                                    digital Tx chirp
                                                    prior to
                                                    transmission and
                                                    ADC'ed Rx signals) </i>N200
                                                  devices with LFTX/LFRX
                                                  daughterboards, that
                                                  work with coherent
                                                  LFMCW chirps, I am
                                                  still seeing a tiny
                                                  drift (both in the
                                                  magnitude and
                                                  frequency) of the
                                                  calibrated 
                                                  back-scatter Rx chirp
                                                  received at time t1
                                                  when compared to an Rx
                                                  chirp received at an
                                                  earlier time t0. <br>
                                                  <br>
                                                </div>
                                                <div>The more the N200
                                                  device runs (e.g., 5
                                                  hours), the greater
                                                  the drift is.
                                                  Obviously, this drift
                                                  is pertinent to both
                                                  the DAC and ADCs and
                                                  the GPS referenced
                                                  clocks of the N200
                                                  devices.</div>
                                                <div><br>
                                                  My questions are:<br>
                                                  <br>
                                                </div>
                                                <div>1- Why I still see
                                                  such drift although my
                                                  devices are synced
                                                  with an external GPS?
                                                  and how do I correct
                                                  for it?</div>
                                                <div><br>
                                                  2- Can the <b>PLL
                                                    Carrier Tracking </b>block

                                                  in GRC be used to
                                                  track and correct for
                                                  such a drift? If so,
                                                  how do I set the
                                                  max/min freq inputs
                                                  for this block?<br>
                                                  <br>
                                                </div>
                                                <div>3- Can <b>AGC2</b>
                                                  or <b>AGC3 </b>block
                                                  be useful in this
                                                  regard? If so, are
                                                  there any examples to
                                                  explain how the input
                                                  parameters of these
                                                  blocks can be set up?<br>
                                                  <br>
                                                  <br>
                                                </div>
                                                <div>Thanks.<br>
                                                  <br>
                                                </div>
                                                <div>Best regards,</div>
                                                <div>Khalid<br>
                                                  <br>
                                                </div>
                                              </div>
                                              <br>
                                            </div>
                                          </div>
                                          <pre>_______________________________________________
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</pre>
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                              <pre cols="72">-- 
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
<a moz-do-not-send="true" href="http://www.sbrac.org" target="_blank">http://www.sbrac.org</a>
</pre>
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    <pre class="moz-signature" cols="72">-- 
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
<a class="moz-txt-link-freetext" href="http://www.sbrac.org">http://www.sbrac.org</a>
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