[time-nuts] Re: Custom Quartz crystals

[Brooke Clarke]

Hi:

IEC 444 is a PI-Netowrk measurement method for crystals.  It is supposed to me more accurate than the method that uses a 
physical CL.
The HP 41900A has the look and feel of the linked PI-Network fixture so may just be a re-branded version.
https://prc68.com/I/4395A.shtml#E5100

-- 
Have Fun,

Brooke Clarke
https://www.PRC68.com
axioms:
1. The extent to which you can fix or improve something will be limited by how well you understand how it works.
2. Everybody, with no exceptions, holds false beliefs.

-------- Original Message --------
> Hi
>
> Thanks to a bit of off list coaching from those who’s memory (obviously)
> better than mine :) :
>
> This is the magic test set that Motorola (and many others) got pretty
> heavily into:
>
> https://isolalab.com/pinetwork.html <https://isolalab.com/pinetwork.html>
>
> The gizmo is right at the top of the page. There’s a nice paragraph next
> to it and a diagram of what’s inside.
>
> The original outfit that made it ( Cathodeon / Pye ) has been out of business
> for quite a while. They apparently made the fixture to support their
> crystal manufacturing business. Just how many fixtures they sold to
> their competitors …. no idea.
>
> Bob
>
>> On Aug 17, 2022, at 8:17 AM, Bob kb8tq <kb8tq at n1k.org> wrote:
>>
>> Hi
>>
>> One “interesting” way to look at this is a “delta F” test.
>> It’s based on a system that (essentially) always measures
>> things at series. You put the (maybe) 20 pf  load cap in series
>> with the crystal and zip off it goes to measure the net result
>> of the crystal at a 20 pf load.
>>
>> Typically you did this by pushing a paddle on a fixture. Yes
>> that’s very specific to one rig up. Turns out that Motorola
>> decided it was a fun thing and we tested a *lot* of crystals
>> that way. It’s been “a while” … but .. fundamental crystals
>> came in at > 400 ppm. Third overtones might be around
>> 30 ppm. Fifth overtones might be around 3 to 5 ppm.
>>
>> No this isn’t for the same crystal or even the same crystal
>> package. It also isn’t for SC cuts, these all where AT’s.
>>
>> … and yes, if I could remember the name if the UK outfit
>> that made the test heads, I’d give them credit for their cute
>> little gizmo.
>>
>> One interesting outcome of testing this way was to spec
>> crystals as some number of PPM off series rather than
>> with a load. Changing the load cap in the fixture was “not
>> done”.  AFIK that was very specific to internal Motorola
>> documents. The only time I saw it used elsewhere was
>> on crystals that operated below series.
>>
>> Bob
>>
>>> On Aug 17, 2022, at 5:28 AM, Richard (Rick) Karlquist via time-nuts <time-nuts at lists.febo.com> wrote:
>>>
>>> It is hard to answer your question.  The tuning range
>>> depends on the varactor(s) used in the respective
>>> oscillators, and the range of the tuning voltages.
>>> I think I could roughly say from memory that putting
>>> in a crystal meant for the other oscillator would
>>> probably result in not being able to reach 10.000000
>>> MHz.  Or just barely reaching it and having no
>>> aging margin.  I had to apply a lot of arm twisting
>>> to Jack Kusters to get him to make the series
>>> resonant (at 10 MHz) crystals.  I made sure that
>>> this was really necessary before going to war on it.
>>>
>>> Rick N6RK
>>>
>>> On 8/14/2022 3:35 PM, Hal Murray via time-nuts wrote:
>>>> Richard (Rick) Karlquist said:
>>>>> We actually used the upper turnover because the E1938 had to operate at
>>>>> ambient up 85  degrees.  BTW, the E1938 crystals had to be calibrated for
>>>>> 10.000000 MHz at series resonance, unlike the 10811 crystals which were
>>>>> calibrated for 20 pF (IIRC).
>>>> How big is the difference between series and 20pF compared to the tuning range?
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