[time-nuts] HP 5061Cs reference question

Tom Van Baak tvb at LeapSecond.com
Sat Dec 6 13:18:07 EST 2014

> Now if the device was on one of those side peaks what would that make the offset at 5 MHz be?.
> I think something like 1 Khz divided by 9192631770. I am sure 5 MHz comes into the calculation.
> Pretty small. But may guess thats what I see. Its 44ns slow over 27 minutes as of yesterday.
> The systems been on 4 days.


40 kHz / 9192 MHz is 4e-6, so you're obviously not locked to one of the 6 wrong peaks.

1 kHz / 9192 MHz is 1e-7, or 100 ns per second, so I don't think you're locked to one of the 2 side peaks either. A 1e-7 error translates to 0.5 Hz out of 5 MHz.

44 ns / 27 minutes time drift = 2.7e-11 frequency offset. Maybe all you need to do is adjust the C-field dial. As a quick test measure the 5061A output frequency at min C-field and max C-field to get an idea of your tuning range. HP used two different ranges on the 5061A. Or measure at each turn of the dial, as I did here:

If you want, perform the Zeeman calibration as described in the 5061A manual. It says "an error of 1% in the Zeeman frequency causes an error of 3.6 parts in 10^12 in the 5 MHz output". 


----- Original Message ----- 
From: "Tom Van Baak" <tvb at LeapSecond.com>
To: "Discussion of precise time and frequency measurement" <time-nuts at febo.com>
Sent: Saturday, December 06, 2014 9:04 AM
Subject: Re: [time-nuts] HP 5061Cs reference question


There are 7 peaks total, about 40 kHz apart (on my 5061A). If you're talking about just the central peak, there are two smaller peaks on either side, about 1 kHz apart. The exact value depends on internal magnetic field, which is specific to each beam tube design.

For some measurements of all the peaks, have a look at:

You can play with the C-field in addition to playing with peaks:
http://leapsecond.com/images/cfield.gif  (578 x 4610 pixels)

For more details search the archives for the word Zeeman. For example:

A nice description from hp how a cesium beam standard works:


----- Original Message ----- 
From: "paul swed" <paulswedb at gmail.com>
To: "Time-nuts" <time-nuts at febo.com>
Sent: Saturday, December 06, 2014 6:11 AM
Subject: [time-nuts] HP 5061Cs reference question

>I have a curious question that really applies to all Cs references.
> Its possible to set them on to the wrong peak.
> Typically in the literature it will speak to at least 3 peaks and you want
> to select the highest central peak.
> However if you select the wrong peak, how much would the output frequency
> be off?
> I had read a tech note for the airforce that seems to indicate its pretty
> easy to get on to the wrong peak.
> Regards
> Paul

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