[time-nuts] Input voltage for Zeeman on 5061A

John Ackermann N8UR jra at febo.com
Sat Jan 22 18:07:45 UTC 2005


The meter readings I'm seeing are valleys of about 18 and the major peak 
of about 22.  The secondary peaks are about 20.  I'm pretty sure I'm 
looking at the close in peaks.

However, when I did that check the loop-closed beam current was about 
17.  After taking those measurements, I bumped the beam I adjustment to 
get it up to 20; the 2nd harmonic was reading 40 both before and after 
that minor adjustment.  I suspect that having slightly higher current to 
begin with might help make the peaks more pronounced.

One thing that's slightly confusing in the manual is the amplitude 
setting of the audio oscillator.  The book says to start with zero and 
increase to the first peak.  Well, when starting at zero there's 
actually a decrease in current as you crank the amplitude up, but I was 
able to spot a small peak at about 800mv RMS, so that's where I left the 
amplitude setting.

At the moment, I'm doing a check against GPS and Loran at the value I 
found (which isn't too far off what Corby set the unit to before 
shipment -- it's at about 4.90 now versus 5.06 before).  I want to let 
that run for at least a few more hours to get a sense of how close it 
is.  After that, I'll go back to experimenting.

John
----
Tom Van Baak wrote:

>John,
>
>Can you quantify that? How many minor divisions
>on the C-field dial and what meter levels do you get
>for the 3 peaks and 2 valleys between the peaks?
>
>Also try recording to 9 or 10 digits the 5 MHz output
>at each peak/valley.
>
>I want to clarify something mentioned a while back.
>The peak(s) and valleys you see when performing a
>Zeeman calibration are the narrow ~500 Hz wide
>center peak. See:
>http://www.leapsecond.com/pages/cspeak/image003.gif
>and
>http://www.leapsecond.com/pages/cspeak/image004.gif
>
>These are not the broad ~40 kHz separated 7 peaks as in:
>http://www.leapsecond.com/pages/cspeak/image001.gif
>
>/tvb
>
>----- Original Message -----
>From: "John Ackermann N8UR" <jra at febo.com>
>To: "Discussion of precise time and frequency measurement"
><time-nuts at febo.com>
>Sent: Saturday, January 22, 2005 08:57
>Subject: Re: [time-nuts] Input voltage for Zeeman on 5061A
>
>
>  
>
>>I tried the 42.82kHz frequency and wasn't able to see any peaks or dips
>>at all.  53.53 gives peaks and dips, but not very pronounced.
>>
>>John
>>----
>>
>>Chuck Harris wrote:
>>
>>    
>>
>>>The Zeeman frequency is a characteristic of the tube.  Most FTS tubes
>>>have their main Zeeman peak at 42.820kHz, and the two peaks on either
>>>side are at 41.800kHz, and 43.800kHz.
>>>
>>>1 Vrms is what the 5061 wants to see (The Zeeman input is a 50 ohm load
>>>IIRC).
>>>
>>>-Chuck
>>>
>>>John Ackermann N8UR wrote:
>>>
>>>      
>>>
>>>>Anyone know how much voltage you need to drive the Zeeman input on
>>>>the 5061A?  I just tried to set mine and found that the maximum
>>>>output from my 3325A (3V RMS) was barely enough to see any wiggling
>>>>at all on the beam current meter  I have another generator that goes
>>>>up to 6V and that got me a bit more, but even then only a few meter
>>>>divisions between peak and dip.
>>>>
>>>>Either I need a heftier generator (or maybe an impedance step-up), or
>>>>we're back to the question of what is the right Zeeman frequency for
>>>>an FTS tube in an HP chassis.
>>>>
>>>>Thanks,
>>>>
>>>>John
>>>>        
>>>>
>
>
>
>
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>  
>





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