[time-nuts] Couple of questions for Racal 1992 owners

iovane at inwind.it iovane at inwind.it
Thu Aug 27 07:39:31 UTC 2009


I have two 1992, and actually one has to terminate the output to see the real waveform.
They have both the 04E option, that I believe is a nice one. In long term measurements, I've found that mine have an aging rate in the range of 1x10E-10 per day, or better (compared to Rb). The crystal is cut to 5 MHz, then doubled.
The time required to stabilize after power on is normal.
Antonio I8IOV


> My 1992 has a similarly ugly reference output - until I terminate it.  
> Then it's a fairly nice square wave between 0 and 1 volt.  Rise & fall 
> times are in the range of 5 ns.  The manual doesn't state what the wave 
> shape is, only that it's > 600 mVp-p into 50 ohms. I have a brochure 
> that says "TTL levels giving approx. 1Vp-p into 50 ohms".  My phase 
> measurements also have a similar amount of 'noise' to yours.
> 
> Which timebase does yours have?  I've got option 4E (similar to 4B).  
> Although the timebase appears to be stable, I've noticed that the 
> counter drifts about 5e-9 during warmup, even when the oscillator has 
> been on standby for many days.  It takes a couple of hours to settle 
> down.  Does yours do anything similar?
> 
> Ed
> 
> John Green wrote:
> > Just acquired a used 1992 off eBay. Excellent, almost like new with manual
> > and even spare fuses. I noticed that the internal reference's waveform is
> > more like a nasty sawtooth than a nice sine wave. Is that normal? Also, when
> > I hook my GPSDO through a two way splitter and two different length cables
> > and measure phase, I get a +\- 3 LSD ambiguity. Is that about right?
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