[time-nuts] retry: PRS10 has spurious frequencies

[SAIDJACK at aol.com]

In a message dated 4/24/2007 15:14:11 Pacific Daylight Time,  
brooke at pacific.net writes:

>>  It is unclear to me if the spurious is normal or not. The spurious of   
>> my PRS10 is 60dB down the 10MHz so it is strange that you see  no  
>> spurious.
>>


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 supply,  
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 :)
 
bye,
Said



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