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<DIV><FONT face=Arial size=2>Here are the Mercury performance figures measured
on the prototype systems. Greg, ZL3IX,<BR>has a similar prototype and has
measured similar figures.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=Arial size=2>Unlike a conventional analogue radio an DDC
receiver will have a sudden overload point<BR>as the ADC reaches full scale.
This overload point is the limiting factor in terms of <BR>performance. In the
case of the ADC used in Mercury the LT2208 is a saturating ADC so <BR>increasing
the input signal beyond the overload point does not produce a sudden
catastrophic <BR>degradation in performance. </FONT></DIV>
<DIV><FONT face=Arial size=2><BR>Pre-amp off</DIV>
<DIV> </DIV>
<DIV>MDS - 117dBm, IP3 +50dBm, Blocking Dynamic range
125dB, overload +8dBm</DIV>
<DIV> </DIV>
<DIV>Pre-amp on </DIV>
<DIV> </DIV>
<DIV>MDS -135dBm, IP3 +30dBm, Blocking Dynamic
range 125dB, overload -10dBm</DIV>
<DIV> </DIV>
<DIV>The IP3 at +50dBm is approximate since its at the limit of my test
equipment.</DIV>
<DIV> </DIV>
<DIV>The MDS was measured in a 500Hz bandwidth. The IP3 is INDEPENDENT of tone
spacing.</DIV>
<DIV><BR>Blocking Dynamic Range was measured at 100kHz and 5 kHz for 1dB gain
compression with similar results.</DIV>
<DIV>The DBR is set by the overload point of the ADC rather than being phase
noise limited.</DIV>
<DIV> </DIV>
<DIV>Greg estimates the phase noise of the 125MHz clock at -149dBc/Hz which is
very <BR>good for a packaged crystal oscillator (NOTE: the 125MHz oscillator was
not phase<BR>locked to a 10MHz reference for these tests).</DIV>
<DIV> </DIV>
<DIV>My pre-amp consisted of a noiseless feedback power FET with 2dB noise
figure and 8dB of<BR>gain driving a Norton BJT stage with 12dB of gain. Greg
used a two stage Norton BJT preamp. </DIV>
<DIV> </DIV>
<DIV>The MDS with the pre-amp off is a little high, most receivers give about
-127dBm. In which<BR>case we may need to use a little pre-amp gain at all times
to reach this level. </DIV>
<DIV> </DIV>
<DIV>Very good figures for a fully digital receiver that should give excellent
performance for<BR>many users.</DIV>
<DIV> </DIV>
<DIV>Thanks to Greg for assisting with these measurements.</DIV>
<DIV> </DIV>
<DIV>73's Phil....VK6APH </FONT></DIV></BODY></HTML>