[time-nuts] The 5MHz Sweet Spot

[Bob Camp]

Hi

One of the often seen statements about jumps is that the time between them increases as the oscillator ages. Obviously that’s only going to apply to certain mechanisms. If you OCXO jumps because there is no solder on the varicap, it may not apply. To the extent it’s true, it’s a much bigger issue for those who buy their OCXO’s straight from the factory than for those who buy them surplus. 

Bob

On Nov 9, 2013, at 7:11 PM, Angus <not.again at btinternet.com> wrote:

> Yes, but as with quartz it varies a lot. 
> 
> I have tested a few LPROs, but have never seen a frequency jump in them. Those with more to test might have seen some jumps, but mine have been well behaved whenever they were being logged anyway.
> 
> I don't remember seeing actual  jumps in the FE5680A's either, although the 2 older style 1pps-only ones did often have retrace jumps (like 5-10ppt) even after a short power down.
> 
> The most obvious jumps I have seem were on a Temex LPRO/LPFRS which also had a borderline low peak Rb voltage, whether that had anything to do with it or not. At first it sometimes jumped in steps of 5-20ppt, and tapping it or even touching the connector on the RF cable from it would also often cause a jump. It was at its worst when I first powered it up, but even after many weeks on, they were still there occasionally. 
> 
> I've also tried a couple of the 9.8304MHz Sa.22c things recently, and other than being very basic spec, one had some fast frequency jumps and the other none that I saw - although near the middle of a 7 week test run it decided to change by 3E-11 over 15 hours or so. That is actually very like what I've seen sometimes in quartz where many days of aging happen in a few hours - I have MTI260's particularly keen on this trick.
> 
> I had originally been interested in investigating jumps, but since they were most obvious in the poorer oscillators my interest waned a bit.
> 
> Doing a search on rubidium frequency jumps turns up a fair bit, although much is on the GPS Rb's which unfortunately will not be cheap surplus any time soon - unless someone really messes up!
> 
> Angus.
> 
> 
> 
> From: "Hal Murray" 
> To: "Discussion of precise time and frequency measurement" 
> Sent: November 3, 2013 9:28 PM
> Subject: Re: [time-nuts] The 5MHz Sweet Spot
> 
> Do low cost recycled Rubidiums have any quirks equivalent to frequency jumps 
> in crystals?
> 
> 
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
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