----- Original Message ----- From: "Matt Ettus" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]>; "Discussion of precise time and frequency measurement" <time-nuts@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 _______________________________________________ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
