[time-nuts] Sound Card Spectrum Analyzer

Gerhard Hoffmann dk4xp at arcor.de
Fri Feb 19 13:16:03 UTC 2010

Bruce Griffiths wrote:
> Not necessarily, it depends on the phase detector circuit details.
> What phase detector output termination network did you use?
> Aren't BF862's somewhat noisier than 2SK369's at low frequencies?
SRA-3H because I had them,  49R9 in series with 3n9 for sum termination.
LC low pass with fairly large capacitance, high load impedance.
as recommended in Crawford, Frequency Synthesize Design Handbook page 11.
he cites
Fisher, M.C. "Frequency Domain Measurement Systems",
10th Annual Precise Time an Time Interval Applications and Planning Meeting
as the source.

I could not see much of a difference between NXP BF862 and Toshiba 2SK369.
BUT  ---  the BF862 has MUCH smaller input capacitance, so one could at 
parallel 3 times as many of them for the same input load.

Now that I have some access to an Agilent signal source analyzer on a 
my own phase noise measurement capability has dropped in importance, so 
I can
concentrate in oscillators. I could re-use them as a clock for a digital 
PN solution with
2* Inphi S&H, 2* state of the art ADCs and FPGA, which is more on my 
home turf.
I think that the Wavecrests use the Inphi S&H, too.


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