On Tue,9/1/2015 2:52 PM, Rick Stealey wrote:
Jim,
I'm duplicating your slide 8 test with my K3 going into a flex 6300.
25 watts
At 80 db down I'm seeing a little over 400 cycles, and a pedestal.
This is K3 with the original synthesizer.
Studying this measurement, I have several thoughts. First, the
resolution bandwidth appears to be about 30-40 Hz at -70 dBc, compared
to 60 Hz for the K3 with P3SVGA. That's very good. Also, those peaks
that show up in the range of 260-310 Hz either side of the carrier are
visible in the waterfall and are moving in the waterfall, so I suspect
they are some sort of modulation. Note that they are not visible earlier
in the waterfall.
Do you know, when you say you see X dbc what effective bandwidth that
is? i.e. how to translate that into signal power in a 1 hz bandwidth
like ARRL does?
No, I don't know, because we don't know the effective bandwidth of our
measurement systems.
Because with the FFT spectrum analyzers there is no fixed bandwidth
filter sweeping across the spectrum.
Right. We've been working with both swept measurement systems like TDS
(Time Delay Spectrometry) and dual channel FFT since 1980. I had a TDS
system in 1982. Cost me $12K.
ex: at 1 khz offset (14051= 5 divisions) phase noise is ~-95 dbc. but
what would that be in a 1 hz bw?
No good answer, for the reason noted above. But this measurement shows
that this test setup is very good for measurement occupied bandwidth as
long as you stay out of non-linearity (that is, either too close to the
top or bottom of the A/D).
By all means save this measurement and compare it with what you see with
the new synth board.
73, Jim K9YC
Rick K2XT
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