Makes sense, my apologies for the snark.
It would be amazing if this thing worked properly with such a huge dynamic range.
Having messed around with the si5351 myself,
I'm fully on board with the notion that some will have a serious gap when
the si5351 output is pushed to 300 mhz.
And others could show a minor "discontinuity" at 300mhz due only to
the switch to using a harmonic.
Jerry
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On Sun, Aug 25, 2019 at 02:19 PM, Warren Allgyer wrote:
My NanoVNA is operating on the fundamental at 300 MHz and on the third
harmonic for the rest of its range. It has no trouble getting to 300 MHz. It
can, at times, display a spike at 300 MHz but that spike comes and goes
depending upon the span selected, prompting my suspicion that it is not real
but an anomaly based on the discontinuity in Si5351 operation that takes place
at the 300 MHz boundary.
It is not that I do not believe 80 dB of dynamic range. Mine would clearly do
80 dB at lower frequencies if the Si5351 output were increased because there
is at least 10 dB of measured headroom on the receiver. But, with the level of
-17 or so dBm at low frequencies, there is simply not enough excitation level
to realize responses at -80 dBc as that level is below the noise floor.
In order to display 80 dB of dynamic range I would need to see a display with
the reference level moved from ¡°0¡± to at least -20 dB and a capital
¡°C¡± and capital ¡°T¡± in the calibration legend to the left of the
screen. Under these conditions, if the displayed noise floor is more than 60
dB down then the dynamic range is indeed 80 dB. Mine will not do that¡¡.
but I am willing to be shown that other iterations can. I just would like to
be sure the measurement is being done correctly to make that claim.
