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" <[email protected]>
To: "Discussion of precise time and frequency measurement" <[email protected]>
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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