[time-nuts] [Fwd: Re: What is the best counter for a Time Nuts?]

hasweb at has.org.nz hasweb at has.org.nz
Tue Oct 14 03:58:45 UTC 2008


Quoting Mike Monett <XDE-L2G3 at myamail.com>:

> hasweb at has.org.nz wrote:
>>
>> Mike Monett wrote:
>>>   > So, assuming my known timebase is "bang on", I know  the frequency
>>>   > of the unknown 10 MHz source to an accuracy of roughly 3e-10  or 3
>>>   > parts in 10 billion.
>>>
>>>   > To get  a  more precise measurement  of  the  frequency difference
>>>   > between the two 10 MHz clocks, I supply the known 10 MHz  clock to
>>>   > the Channel  A  input  of an HP  3575A  Gain-Phase  meter  and the
>>>   > unknown 10  MHz  clock to the channel B  input  of  the Gain-Phase
>>>   > meter.
>>>
>>>   Another very  difficult instrument to find any data on.  The  best I
>>>   could find shows it has an accuracy of ± 0.5 degree and resolution
>>>   of 0.1 degree.
>>>
>> Try the agilent website for the manuals not yet readily available
>> For directions visit:
>> www.hparchive.com <http://www.hparchive.com>
>>
>> There is a 3575A manual for downloading at the Agilent ftp link.
>> If you read it you will find that the specified error with 10MHz
>> inputs is much larger: 10-20 degrees or so.
>>
>> Bruce
>
> There is nothing in the hparchive site, and I don't have the Agilent ftp
> site url.
>
> Could you give a direct link to the 3575A manual?
>
> The basic principle is sound. It should be very easy to make a simple PWM
> circuit to measure phase accurately at 10MHz. You mentioned the same thing
> earlier. Why not post the schematic so we can take a look?
>
> Mike Monett
>
> _______________________________________________
>

Mike

I did some time ago, for some examples (other implementations are also  
possible ) see:

http://www.ko4bb.com/~bruce/LinearPhaseComparators.html

HP used to make the K345991A phase comparator for this purpose.
They also produced other variants for use with their caesium beam standards.


The quickest and easiest is to use the AD9901 phase detector as it  
only has a few ns of non linearity at the end of the range. For higher  
resolution just add a sigma delta ADC.


The Agilent link link:

ftp://ftp.agilent.com/pub/manuals/

is actually at the bottom of the text at the top of the equipment page  
on the hparchive site

Sorry I cant post the site as a link as I am temporarily using a  
backup email server as the regular one can't yet find the new time  
nuts server.


Bruce




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