[time-nuts] Zeeman frequencies

jim_johnson at agilent.com jim_johnson at agilent.com
Sat Jan 15 02:21:21 UTC 2005


Hi John,

   Just thought I'd add a little to this discussion.
The Zeeman frequency "belongs" to the tube, not the
electronics.  The Zeeman frequency and the C-field setting
are closely interrelated and in the 5061A/B the setting
of the Zeeman frequency to the value specified in the
manual allows the C-field to be the proper value to put 
the tube on the correct frequency.  Frequency adjustments
(small) are made in the 5061 with the C-field knob, but
that is not the best way to do it as changing it moves
the "operating point" away from the optimum point, where
secondary effects are least able to pull the frequency
away from the place where the second is defined in a 
primary standard.  In the 5071A the Zeeman frequency is
a fixed value and the C-field is servoed so that it never
moves.  The frequency of the 5071A is changed (steered)
by changing a DDS (synthesizer) value, a modern electronic
luxury that was not available in the 1960's when the 5061
was designed.  So to put a different tube, say an FTS tube,
into a 5061A/B requires the C-field and Zeeman frequency
to match the tube manufacturer's requirements as closely
as possible.  Hope this helps rather than muddy the waters
even further.  :-)

73,
Jim
Agilent Laboratories
Precision Instrumentation Lab
Palo Alto, CA
jim_johnson at agilent.com



>-----Original Message-----
>From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com]On
>Behalf Of John Ackermann N8UR
>Sent: Wednesday, January 12, 2005 5:44 PM
>To: time-nuts at febo.com
>Subject: [time-nuts] Zeeman frequencies
>
>
>Hi --
>
>I just got off the phone with Corby Dawson who was helping me through 
>the power-up of my newly acquired 5061A.  (The replacement FTS 
>tube had 
>slipped during shipment, breaking the HV connector for the ion pump.  
>It's fixed now, and I have a nice green "Continuous Operation" light.)
>
>Anyway, I asked him about the Zeeman frequency for an FTS vs HP tube.  
>His answer was that the proper frequency depends on the electronics in 
>the chassis, not the tube.  HP specified two different frequencies, 
>42.82 (in the early manuals) and 53.53kHz.  Either one will work, but 
>the higher frequency gives slightly better accuracy (maybe a sharper 
>peak, so better resolution?).  The 5061B manual says that 100Hz of 
>Zeeman offset is equal to 1x10e-12.
>
>John
>
>
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