www.febo.com

Sulzer Frequency Standards

Sulzer 2.5 Performance Data

In the early 1960s, Sulzer Laboratories produced one of the finest quartz frequency standards ever offered commercially. Even 40 years later, these standards turn in superlative results.

I now own three Sulzers, one of which I've had for over 15 years. I was lucky enough to have that unit evaluated last year by an anonymous friend who has access to the best in frequency analysis tools, including a hydrogen maser. These charts show the performance of this model 2.5 standard as of August, 2001 -- about 40 years after its manufacture.

Aging

Aging is how the crystal frequency changes over a long time period. You'd expect a crystal this old to be well aged by now, and you'd be right. Aging typically decreases with continuous operation, and my friend only had the unit running for a few weeks. Over that time, he saw the aging improve from 1x10^-10/day to 5x10^-11/day. I suspect that after a few months of operation, the aging would be down to only a couple of parts in 10¹¹/day.

Short and Medium Term Stability

This chart and table show thoroughly respectable performance. Stability of <4x10^-12 at one second is excellent. The HP 10811D/E, a very good oscillator of recent vintage, and the Austron 1250A, another fine standard, are both spec'd to perform at <5x10^-12 at one second.

At medium term (minutes to hours), the Sulzer is tremendous; the performance of 1.2x10^-12 at 100 seconds is substantially better than an HP 10811D/E (spec'd at <5x10^-11) or an Austron 1250A (spec'd at 1x10^-11 for 120 seconds).

However, to be fair, the 10811D/E is better for averaging times of less than one second; its specification is <5x10^-12 at 0.1 second, compared to the Sulzer's 9.9x10^-11.

By the way -- although this unit looks pretty good, there are other Sulzer 2.5s out there with even better performance. See Tom Van Baak's www.leapsecond.com site in the undocumented www.leapsecond.com/museum section for performance reports on two pretty fantastic model 2.5C units with 1-second stabilities in the 10^-13s: (a) the first one and (b) the second one.