[time-nuts] HP5370A vs B version

[Bob kb8tq]

Hi

If you have a pile of 10811’s a fun experiment is to put them on power for a couple months.
Log the frequency once a day or so and watch how they “drift in” to whatever the final 
frequency is. Because they are an un-sealed unit, power off storage is not kind to them.
Some take a long time to recover. A few never really seem to settle down. Since the ones
that don’t settle are not of a lot of use, they often head off to eBay and get passed from 
hand to hand over the years. In some cases you *can* find a problem component. There
aren’t a lot of people who dig that deep *and* get it right. 

Bob

> On Jul 20, 2019, at 11:35 AM, Taka Kamiya via time-nuts <time-nuts at lists.febo.com> wrote:
> 
> Thank you.
> I really do not want to buy from eBay.  So far, none showed up with zero problems.   There's always something.  My intent is to lock it to house standard which is a GPSDO.  I have lots of 10811 here but I don't know when they were made.  All I know is they are all 10811-6011.  You are right - especially for an instrument like this, standard is extremely important.
> 
> --------------------------------------- 
> (Mr.) Taka Kamiya
> KB4EMF / ex JF2DKG
> 
> 
>    On Saturday, July 20, 2019, 11:02:19 AM EDT, Bob kb8tq <kb8tq at n1k.org> wrote:  
> 
> Hi
> 
> If you are buying them on eBay, it is not at all clear which OCXO your A or B will show up 
> with. The 10811’s get swapped back and forth with earlier units in a lot of used gear. One
> might *think* it’s a one way exchange, but I’ve seen it go both ways. 
> 
> If you lock the counter to an external standard, it really does not matter a lot which OCXO
> is in it. 
> 
> Bob
> 
>> On Jul 20, 2019, at 4:21 AM, Frank Stellmach <frank.stellmach at freenet.de> wrote:
>> 
>> Hi Mr. Taka Kamiya,
>> 
>> the B version has a 500MHz front end, copied from the HP5345A, with a matched pair of amplifier / Schmitt trigger hybrids.
>> The A version has separate amplifier and Schmitt trigger ICs.
>> 
>> There were also changes on the trigger circuit.
>> 
>> Then the B version has a simplified µP board, has the OCXO (10811-60111), which is a must for absolute T.I. and frequency measurements.
>> 
>> Maybe the firmware was also improved a bit, I think mainly concerning the GPIB steering of the trigger circuit.
>> 
>> This T.I. counter is supposed to be superior over others of that era, because this special time interpolator was more linear.
>> 
>> I really love mine, so I don't want to sell it.
>> 
>> Frank
>> 
>> 
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> 
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