[time-nuts] Ultra High Stability Time Base Options for 53132A

[Magnus Danielson]

Hi,

The buffer transistors has not AC-bypass of the emitter resistance, so 
that the DC current becomes large and thus contributes flicker noise.

The comparator at the bottom isn't doing a beutifull work of squaring 
things up without contributing noise, considering the sine output of the 
10811.

Was that it, Rick?

Cheers,
Magnus

On 04/12/2015 06:50 PM, Tom Van Baak wrote:
> Hi Rick,
>
> It is our good fortune that some years ago Agilent/Keysight released the schematics to the 53131A/53132A counters:
> http://literature.cdn.keysight.com/litweb/pdf/5989-6308EN.pdf
>
> Have a look and see if you can recreate the details that you remembered.
>
> I too have noticed on some tests that the counter seems to ruin the benefit of a good external timebase. This is even more true of the newer 53230-series counters. Maybe get rid of the PLL and use a int/ext toggle switch like the 70's.
>
> So it would be nice if you or other circuit experts on the list could point out the flaw(s) -- I'm sure a couple of time nuts would even be willing to mod their 53132A boards based on some suggestions on what to try.
>
> Thanks,
> /tvb
>
> ----- Original Message -----
> From: "Richard (Rick) Karlquist" <richard at karlquist.com>
> To: "Discussion of precise time and frequency measurement" <time-nuts at febo.com>
> Sent: Sunday, April 12, 2015 8:30 AM
> Subject: Re: [time-nuts] Ultra High Stability Time Base Options for 53132A
>
>
>> On 4/12/2015 1:03 AM, Adrian Godwin wrote:
>>> What caused that degradation ? I'm interested in dos/don'ts for best use of
>>> a 10811.
>>>
>>
>> I don't remember the details much after 25 years, but
>> basically they have a distribution amplifier that
>> allows for internal or external 10 MHz and what I
>> remember is that I looked at the schematic and
>> concluded that no one with a background in precision
>> time and frequency would design it that way.  And
>> it turned out that the person who designed it did
>> not have any such background.  I vaguely require
>> some measurement that had disappointing results that
>> caused me to want to look at the schematic of it
>> in the first place.
>>
>> Rick
>
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