[time-nuts] HP 5334 oscillator performance

John Ackermann N8UR jra at febo.com
Thu Dec 7 16:40:33 EST 2006


But I should say that despite the bad oscillator (I think all of four or
five of them I own came with the high-stability option; maybe that's
why!), the 5334A/B is a really capable counter, and with eBay prices
sometimes below $100, they are a great value for money.  The fact that
there's no fan noise is just a bonus. :-)

John
----

Rick Karlquist said the following on 12/07/2006 04:15 PM:
> I was the project manager of the 5334B, which was a reduced
> factory cost replacement for the 5334A.  Of course I thoroughly
> evaluated the 5334A before deciding what changes to make.  I will
> apologize on behalf of the company for that oscillator
> in the 34A.  It is a really poor design.  Giving the 5334A project
> team the benefit of the doubt, I guess the philosophy was that
> the built in oscillator is for very non-critical applications and
> they didn't want to increase the cost to those users but putting
> a decent oscillator in the standard counter.  Many users were like
> us and had a house frequency standard, so we never used a built in
> oscillator in a counter.  Due to time and cost pressures, we unfortunately
> inherited the same oscillator in the 5334B.
> 
> So in both products, please plan on getting a 10811 or using an
> external frequency reference.
> 
> Rick Karlquist N6RK
> Project manager, 5334B, circa 1986
> 
> 
> 
> Colin Bradley wrote:
>> I recently took one of my 5334A's off of the house standard to lend to a
>> friend. I thought it a good idea to check the onboard oscillator before
>> lending it out. Both of my 5334A's lack Opt 10 oscillators. This
>> particular unit was almost 40Hz high in frequency. I tried to set it to
>> frequency and had trouble getting it closer than 2Hz. The set-ability was
>> very poor. I checked the service manual and found that HP only specified a
>> final frequency within 8Hz. I can now see why. I then turned the
>> instrument off for 12 hours. The next day I powered the unit back up. The
>> oscillator was 20Hz higher than where I had measured it at shutdown the
>> night before. It took well over an hour for it to re-stabilize and
>> overshot the previous set point by 2Hz. At this point I decided to lend a
>> Heathkit IM-2420 to the friend and continued experiments with the 5334A.
>>
>> I now took the second 5334A down and ran the same tests on it. This
>> instrument was somewhat better but still shared many of the problems the
>> first unit.
>> 1)                  60+ minutes to stabilize after power-up. Oscillators
>> would start out 9 -- 19Hz high and settle in at +- 1Hz.
>> 2)                  Poor retrace at turn on. Final settling frequency can
>> vary by 1Hz.
>> 3)                  Poor set-ability due to the ceramic trimmer.
>> 4)                  Oscillator pulling of 2 -- 3Hz when I connected another
>> counter to the rear panel oscillator jack. The oscillator buffer is on the
>> same ECL chip as the oscillator.
>> After looking at the circuit I decided that a new TCXO would be a better
>> solution than trying to modify the existing circuit for better
>> performance. Since these units are used at room temp most of the time, I
>> need not worry about a wide temp range specification.
>>
>> I set the following goals for the replacement oscillator.
>> 1)                  Improvement of stability by an order of magnitude and
>> set-ability of two orders of magnitude.
>> 2)                  Replacement to be built on a circuit board that would
>> mount in the oven oscillator connector on the main circuit board.
>> 3)                  Use of the full time 24vdc at this connector to power
>> the oscillator at all times. Use of an on-card battery supply for
>> oscillator backup.
>> 4)                  Cheap
>> 5)                  Use of readily available TCXO oscillator module. After
>> checking Mouser and Digi-Key I settled on a Mouser supplied FOX801BE 10mHz
>> unit @ $13.46. to start my experiments. This oscillator draws only 2ma.
>> and frequency is set by an external trim pot.
>>
>> I would be interested in the experiences of others with respect to the
>> performance of their non-oven 5334's (or 5328's) and ideas that support
>> the design goals. Thanks
>> Colin
>>
>>
>>
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> 
> 
> 
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