[time-nuts] Oscilloquartz 4532 GPS receiver
John Miles
jmiles at pop.net
Fri May 18 00:42:22 UTC 2012
> I saw that on eBay, it is great to see a fellow Time Nut won it. I would
think
> Phase Noise is excellent with the 8663, although I would prefer a version
with
> discrete SMA's on the outputs.
It's not very quiet, unfortunately, but I'll bet this one would look better
if I were to remove it from the board. Note the slight elevation in the
noise trace that begins around 500 Hz and continues through 10 Hz, obscuring
the usual 1/f corner. That suggests that either the close-in noise is
artificially high, or the broadband floor is... or perhaps both.
OSA's specifications for the 8662/8663 appear to be unusually conservative.
The data sheet calls for -80 dBc/Hz at 1 Hz, and it would be surprising if
it were really that noisy, or even close.
Another artifact you can see is a small spur that can probably be blamed on
the flashing LED. The LED and its associated PCB traces is not far from the
DB-9 output jack. I actually thought it seemed to be blinking a little bit
faster than 1-pps, and sure enough you can see a small bump around 0.9 Hz.
Not a smoking gun but it does look suspicious.
-- john
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