[time-nuts] Allan Deviation -> continuing saga...

Dr Bruce Griffiths bruce.griffiths at xtra.co.nz
Mon Oct 30 04:49:44 EST 2006

John Miles wrote:
> Definitely an interesting chart.  I don't know how much stock I'd put in it,
> though.  The figures cited are, in some cases, much worse than those
> published elsewhere and observed personally.
> I didn't look at all of the test circuits, but there are more things wrong
> with the LT1016 test circuit on page 19 than in the entire QEX article that
> caught so much flak recently. :-)
> -- john, KE5FX
>> -----Original Message-----
>> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com]On
>> Behalf Of Richard H McCorkle
>> Sent: Sunday, October 29, 2006 10:33 PM
>> To: Discussion of precise time and frequency measurement
>> Subject: Re: [time-nuts] Allan Deviation -> continuing saga...
>> I had been using the Shera HC4046 input circuit for my 10811
>> GPSDO input until I read the test results in the LPRO manual
>> http://www.symmetricom.com/media/pdf/manuals/man-lpro.pdf
>> (Table 3-1 on Pg 18) showing the results of testing various TTL
>> converters for relative phase noise. The conversion techniques
>> document at http://www.wenzel.com/documents/waveform.html
>> has a circuit for using a tuned LC network to increase the sine
>> output from an oscillator to drive a biased gate input. I did some
>> testing of my own and found that using a biased AC04 gate using
>> the Wenzel circuit with no input resistor, C = 100pf, L = 2.7uh,
>> input directly from the 10 MHz 10811 gave the lowest phase noise
>> combination for my GPSDO input.
>> You may want to give this a try.
>> Enjoy!
>> Richard
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The MC10ELT21D circuit depicted in figure 3.4 on P19 will not work if 
wired as shown.
The 47.5 ohm resistor to ground disturbs the dc biasing at the input.
Attempting to sink about 45mA from the Vbb reference pin is probably not 
a good idea.
If the 47.5 ohm resistor is replaced by a 200 ohm resistor from ground 
to the other side of the 0.1uF input coupling capacitor, then the dc 
biasing will be correct and the circuit RF input impedance will also be 
approximately 50 ohms.


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