[time-nuts] My Racal-Dana 1992

Chuck Forsberg WA7KGX N2469R caf at omen.com
Sun Dec 18 11:54:58 EST 2011


The fine frequency control on my 1992 with 9462 has a range of 1 Hz.
It is multiple turns end to end, which I did not count.
There is noticeable friction on the fine freq adjustment.
The slight end play (backlash) between screwdriver and the adjustment makes
fine adjustment difficult.

It has not occurred to me that either the coarse or fine adjustment has 
detents.

The accuracy spec is based on three months of continuous operation.
Not likely in this day and age.

On 12/18/2011 06:17 AM, Ed Palmer wrote:
> I haven't seen a capacitor with detents.  Could the fine adjustment be 
> a multi-turn pot?  I've seen detents with those.  I looked at mine but 
> couldn't tell.  A pot would mean voltage control.  Maybe we could 
> build a GPSDC (GPS Disciplined Counter).  Yes, I'm kidding.  I think.....
>
> Ed
>
>
> On 12/18/2011 1:21 AM, Charles P. Steinmetz wrote:
>> It turns out that I unfairly maligned the 1992 (and the 9462 
>> oscillator, option 04E) when I accused it of poor oscillator 
>> "settability."  I was inspired by the recent discussions to have 
>> another crack at mine, and they can, in fact, be set very 
>> accurately.  One of mine has been reading "000.000000 E-3" for about 
>> 24 hours now, hooked to a Thunderbolt and using the 10-second gate.  
>> The other has been toggling between "999.999999 E-3" and "000.000000 
>> E-3."  (This is how mine are used --- perpetually reading the shop 
>> standards to give an independent reality check on their condition.)
>>
>> Walking the oscillators to 0 is tedious and time-consuming, but not 
>> difficult.  I think I must not have been sufficiently patient in the 
>> past.  The fine adjustment has detents -- if you adjust it slowly, 
>> you can count the clicks.  On both of mine, each click adjusts the 
>> oscillator frequency about 3 mHz (CW lowers the oscillator 
>> frequency/raises the displayed frequency).  Interestingly, when you 
>> are close to zero and adjusting the oscillator only a few clicks at a 
>> time, it takes off in the opposite direction and peaks at a MUCH 
>> greater offset than the eventual increment, then returns and 
>> overshoots in the direction of the adjustment (again, quite a bit 
>> further than the eventual increment), and finally settles to its new 
>> value, with another cycle or two of smaller +/- overshoots around the 
>> final value.  It takes at least 1/2 hour to settle within a count or 
>> two of the eventual final value, and several hours before you can be 
>> confident that it has settled to its new value.
>>
>> Best regards,
>>
>> Charles
>>
>
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-- 
Chuck Forsberg WA7KGX N2469R     caf at omen.com   www.omen.com
Developer of Industrial ZMODEM(Tm) for Embedded Applications
   Omen Technology Inc      "The High Reliability Software"
10255 NW Old Cornelius Pass Portland OR 97231   503-614-0430





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