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

WarrenS warrensjmail-one at yahoo.com
Thu Aug 27 19:33:12 UTC 2009


My typical  Dana 1992 performance with the good OXCO is: (sample size of ONE) 

 4 year average aging rate 0.2 e-10 /day  (Attached)
Day to Day uncertainty around 3 e-10 (same conditions each day, morning at same room temp, reading 1 min after turn-on from standby)
Turn on warm-up drift  First 15 sec =1e-10,  First 1 min = 2 e-10
Warm up 1+ hr about =1e-9
OSC stability throughout the day after 1 hr turn (due to changing line, room temp, etc about 5e-10)
Time interval noise measurement of less than 1 ns (no 1 count jitter about 1/2 the time as the delay between signals change). 
(Using two Square wave inputs from separate low noise sources , the first is 100 Hz the second is 100KHz, so max of 100us delay.)
Turn on data above is Always from standby, and When not using the unit,  it is always in standby, except for a couple of times per year when power fails.

For your ambiguity test to eliminate LOTS of possible external noise sources, 
try  feeding it a single good square wave in the range of 10 Hz to 10MHz, (Rise & fall times in the 5ns range)
Trigger on common, start slope to positive, stop slop set to neg, 
Use and the trigger level of each channel to cause fine delay adjustment of  + - 5ns between signals.
Mine has noise mostly under 1 ns count. i.e can adj the trigger level so jitter is less than or equal to 1ns.

I have not looked at OSC out for a long time, most data above is from measuring the 10 sec freq average of a 10MHz. GPS tracked Osc
 
ws
***********
From: <iovane at inwind.it


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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