<html><body><div style="color:#000; background-color:#fff; font-family:times new roman, new york, times, serif;font-size:12pt">Hi Phil,<br>Thanks for confirming that the adc overload is triggered by the ADC overflow output pin, as I suspected. As you say its going to be literally 0dBFS!<br>Yes, Powersdr is fully calibrated and the s meter reads spot on in dBm with a sig gen applied to the input.<br>So are you seeing the same ~7dB difference I noted?<br>Really my question is I suppose, what is the meter indicating when set to ADC L or ADC R, it looks like the power in the decimated bandwidth I and Q?<br>How is it calculated?<br>KISS Konsole reads spot on also (in dBm) but does not display wideband total power i.e. ADC dBFS, might be a nice thing to add?<br>Thanks,<br>Andrew<br>G4XZL<br><div><span><br></span></div><div><span></span></div><div><br></div> <div style="font-family: times new roman, new york, times, serif; font-size: 12pt;"> <div
style="font-family: times new roman, new york, times, serif; font-size: 12pt;"> <div dir="ltr"> <font face="Arial" size="2"> <hr size="1"> <b><span style="font-weight:bold;">From:</span></b> Phil Harman <phil@pharman.org><br> <b><span style="font-weight: bold;">To:</span></b> Andrew <irbsurfing@yahoo.co.uk>; hpsdr@lists.openhpsdr.org <br> <b><span style="font-weight: bold;">Sent:</span></b> Wednesday, 17 October 2012, 11:53<br> <b><span style="font-weight: bold;">Subject:</span></b> Re: [hpsdr] Problem with Powersdr 2.2.3 and Hermes<br> </font> </div> <br><div id="yiv1936885895">
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<div style="FONT-STYLE:normal;DISPLAY:inline;FONT-FAMILY:'Calibri';COLOR:#000000;FONT-SIZE:small;FONT-WEIGHT:normal;TEXT-DECORATION:none;"><font face="Arial" size="2">Hi Andrew,</font></div></div>
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<div style="FONT-STYLE:normal;DISPLAY:inline;FONT-FAMILY:'Calibri';COLOR:#000000;FONT-SIZE:small;FONT-WEIGHT:normal;TEXT-DECORATION:none;"><font face="Arial" size="2">In answer to your questions:</font></div></div>
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<div><br>What triggers the overload warning, is it the actual ADC overflow
output or triggered by the input level exceeding a certain <span id="yiv1936885895misspell-6" class="yiv1936885895mark">dBFS</span> level determined in
software (if so, what is it -1<span id="yiv1936885895misspell-7" class="yiv1936885895mark">dBFS</span> or 0<span id="yiv1936885895misspell-8" class="yiv1936885895mark">dBFS</span> etc??)</div>
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<div><font face="Arial" size="2">There is a pin on the LTC2208 that gets set when
the ADC overloads. It’s this pin state the gets sent to the PC via the C&C
data bits in the USB protocol. Not sure exactly when this gets triggered
but I would expect at +/- full scale. </font></div>
<div><br>Incidentally, I notice that there is about as far as I can estimate a
-7dB (maybe its 6dB, can't tell) difference between ADC input level (<span id="yiv1936885895misspell-9" class="yiv1936885895mark">dBFS</span>) and the level
indicated on the <span id="yiv1936885895misspell-10" class="yiv1936885895mark">Powersdr</span> s meter set to read ADC level.</div>
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<div><font face="Arial" size="2">Have you calibrated PowerSDR with a known signal
level at the antenna socket?</font></div><font face="Arial" size="2"></font>
<div><br>Is there any way to observe the actual ADC <span id="yiv1936885895misspell-11" class="yiv1936885895mark">wideband</span> level in <span id="yiv1936885895misspell-12" class="yiv1936885895mark">dBFS</span>??</div>
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<div><font face="Arial" size="2">KISS Konsole will display either the actual I and Q
data being sent to the PC (after filtering and decimation) or an FFT of a 16k
block of contiguous samples taken directly out of the ADC – i.e. the
wideband 0-55 MHz bandscope display. At least with my Hermes and Mercury
boards the displayed level is within 0.5dB of a signal from my HP8640B signal
generator. </font></div>
<div><font face="Arial" size="2"></font> </div>
<div><font face="Arial" size="2">73 Phil...VK6APH
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