[time-nuts] Sub Pico Second Phase logger

Bruce Griffiths bruce.griffiths at xtra.co.nz
Sun Dec 21 22:08:30 UTC 2008


Joe

Joe Gwinn wrote:
> Bruce,
>
> At 9:50 PM +0000 12/19/08, time-nuts-request at febo.com wrote:
>   
>> Message: 8
>> Date: Sat, 20 Dec 2008 10:50:46 +1300
>> From: Bruce Griffiths <bruce.griffiths at xtra.co.nz>
>> Subject: Re: [time-nuts] Sub Pico Second Phase logger
>> To: Discussion of precise time and frequency measurement
>> 	<time-nuts at febo.com>
>>
>> Joe
>>
>> Joe Gwinn wrote:
>>     
>>>  Bruce,
>>>
>>>  At 3:54 AM +0000 12/19/08, time-nuts-request at febo.com wrote:
>>>  
>>>       
>>>>  Message: 6
>>>>  Date: Fri, 19 Dec 2008 16:54:12 +1300
>>>>  From: Bruce Griffiths <bruce.griffiths at xtra.co.nz>
>>>>  Subject: Re: [time-nuts] Sub Pico Second Phase logger
>>>>  To: Discussion of precise time and frequency measurement
>>>>         
>>  >>	<time-nuts at febo.com>
>>     
>> [snip]
>>  >> I'll breadboard an oscillator over the holidays and take some samples.
>>     
>>>>    
>>>>         
>>>  A rainy-day activity for sure.   In the Boston area, the issue is
>>>  snow - a noreaster is just now starting, with a foot of snow expected.
>>>
>>>  Joe
>>>
>>>  
>>>       
>> AFAIK it has never snowed here.
>>     
>
> So it instead rains heavily?
>
>
>   
Yes, it does rain heavily from time to time but nothing like a monsoon.
>> It does snow on the central NI Plateau but not usually in December.
>>     
>
> Well, I've just dug out of 1.5 feet of snow already, and it continues 
> to snow.  The threat is that later we will get rain, and then it will 
> all freeze into solid ice.  This in the Boston area.
>
>
>   
>> I'll start with a diode limited (soft clamps - resistance in series with
>> diodes) oscillator and move to a lower distortion one if necessary.
>>     
>
> What distortion level do we need?  Given that the parts cost nothing, 
> I'd be tempted into some overkill.
>   
At some stage we need to emulate the distortion level that is likely
from the mixer output which could be as high as a few percent depending
on the RF input level.
Saturating the Mixer RF port as is usually recommended will increase the
distortion.

May build a quadrature oscillator as this then allows testing with the 2
sound card channels either driven in quadrature or in phase.
Can either use diode soft clamping or a photoresistor based AGC to
control the output level.
> Joe
>
>   
Bruce




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