[time-nuts] How Rubidiums make their frequency

Dave Brown tractorb at ihug.co.nz
Wed Apr 19 17:13:08 EDT 2006


----- Original Message ----- 
From: "Matt Ettus" <boyscout at gmail.com>
To: <K3IO at verizon.net>; "Discussion of precise time and frequency 
measurement" <time-nuts at febo.com>
Sent: Thursday, April 20, 2006 7:55 AM
Subject: Re: [time-nuts] How Rubidiums make their frequency


> Since we can now make DDS's with arbitrary frequency resolution, 
> could
> you make an Rb oscillator without the magnetic field adjustment?

 snip---

I suspect the FEI 5650 series does just that- a 50.255+ MHz VCXO is 
'locked' at 1/136 of the 6.8GHz Rb resonance and there is no 'user' 
adjustment provided for the physics package.  I suspect the magnetic 
field IS preset in the factory but thereafter intended to be left well 
alone.
 The 50.255+ VCXO drives an AD9830-all fine tuning of the output 
frequency takes place by setting the DDS.
Can anyone comment further on this?

On a related issue- the physics package in these units draws a 
significant current at startup- I'm considering current limiting the 
suppy until the current drops back to a lower value-I guess this 
delays the warmup somewhat but it would reduce the current required 
from the supply to the steady state value, for example, thus allowing 
a smaller power supply rating.
 But is this a practicable idea and if so, is it likely to have a 
detrimental effect on the physics package?

DaveB, NZ




-- 
No virus found in this outgoing message.
Checked by AVG Free Edition.
Version: 7.1.385 / Virus Database: 268.4.4/318 - Release Date: 18/04/2006





More information about the time-nuts mailing list