[time-nuts] Wavecrest noise measurement hardware
jmiles at pop.net
Wed Apr 25 14:43:30 EDT 2007
As an aside, how do the Wavecrest machines work? Do they just run the
signal into a low-jitter ADC with a high-quality clock and derive all the
timing information digitally, or is the box full of low-noise tunable
synthesizers, mixers, filters, and the usual stuff?
-- john, KE5FX
> Hi Henk,
> try running your PRS10 from a Pb battery, with nothing else
> connected (no
> RS232 etc).
> The plot I sent you was from a PRS running from a switching power
> with RS-232 connected to some other stuff.
> Also, try making the sine wave of the PRS10 into a nice, fast edge rate
> square-wave with a Fairchild NC7SZ04 driver inverter for example.
> The Wavecrest
> units don't work as well with sine waves as with square waves. On
> the SZ04, put
> a 10nF cap in series to the input, and a 1 MEG resistor from
> it's input pin
> to it's output pin. Feed the chip from a very low noise 5V power source.
> Insert a 40-50 Ohm resistor into the output path going to the
> coax. Put an
> attenuator/AC-coupler into the coax so the Wavecrest doesen't get
> overloaded by
> the 2.5Vpp DC signal. Result: low noise comparator/buffer :)
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