[time-nuts] Lucent RFTG-XO performance...
John Ackermann N8UR
jra at febo.com
Thu Nov 6 13:12:49 UTC 2008
Hi Bill --
I haven't done any more testing, but I'm pretty convinced that there is
something wrong with my hardware, though the monitoring software didn't
indicate any obvious problems. I need to go back and revisit, but due
to a bunch of health problems earlier this year (now just about over
with), I haven't gotten very much done in the basement for a while.
John
----
Bill Hawkins wrote:
> John,
>
> Back in February, you looked at the Lucent GPSDO and declared it the
> worst you'd seen.
>
> Did you ever update that opinion? Is the complete set for $400 not worth
> buying if you
> have a pair of Z3801s that perform some heroic jumps? This is just a
> hobby, not long
> baseline interferometry.
>
> Bill Hawkins
>
>
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> Behalf Of John Ackermann N8UR
> Sent: Sunday, February 03, 2008 7:18 PM
> To: Discussion of precise time and frequency measurement
> Subject: [time-nuts] Lucent RFTG-XO performance...
>
> Has anyone here done any performance measurements of the Lucent RFTG-XO
> unit? I am testing one now and getting extremely unimpressive results,
> and wonder if anyone else has looked closely at these things.
>
> What I'm seeing is almost flat ADEV in the low to mid 10s from 1 second
> out to 40,000 seconds. At 100,000 seconds, it drops to the high 11s.*
> To this point I haven't seen anything that looks like the normal GPSDO
> characteristic of a rapid ADEV improvement from around 1000 seconds or
> so. In fact, this is about the flattest ADEV plot I've ever seen from
> an oscillator.
>
> The frequency difference plot** shows a bang-bang effect of about
> 1.6x10e-9 over the course of a few minutes. This seems to go on
> continuously (at least over the 4 days of data so far). That certainly
> explains the mediocre ADEV performance.
>
> The thing does appear to be locked to GPS, but if my unit is working
> properly, it's about the worst performing GPSDO I've seen.
>
> By the way -- to do this test, I started with both the -XO and -RB units
> online and interconnected the way they were supposed to be. After a
> couple of days of operation, I pulled the interconnect cable and the -RB
> went off line, while the -XO came on. I then started data collection.
> After I'm satisfied with the amount of XO data I have, I'll reconnect
> the cable and do the same test on the -RB side. The full set of plots
> is at http://www.febo.com/pages/oscillators/rftg/ and will be updated as
> I get more data.
>
> John
>
> * http://www.febo.com/pages/oscillators/rftg/rftg-xo_cs1-adevplot.png
> ** http://www.febo.com/pages/oscillators/rftg/rftg-xo_cs1-freqdiff.png
>
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