Walter said:
"Also on an unrelated topic, I found an HP 59309A HPIB clock on a forgotten
shelf and looked at it, and was surprised to see such a poor primary time
standard oscillator inside, just a 1Mhz crystal using a cmos buffer oscillator.
It can accept an external standard, but it did feel odd for a device that is
meant to provide coordinated system time to be so modestly executed. it's like
an uncorrected PC desktop clock." Doesn't this policy actually help prevent the
"two clocks problem"? If every piece of equipment has its own frequency
standard, then how do you compare anything? OTOH, if you buy one piece of
equipment with a 10811 (or Rb or Cs or GPSDO) and use that to feed the rest,
then even it's wrong, they're all wrong by the same amount.
Bob
From: walter shawlee 2 <[email protected]>
To: [email protected]
Sent: Saturday, January 28, 2017 11:29 AM
Subject: [time-nuts] distribution amp question + hp 59309A
I notice that in the distribution amp being discussed at the moment,
the BNC output connectors are grounded, and tied to the chassis,
which in turn has a grounded emi line filter. this seems like an unavoidable
noise pathway to me.
I notice that some commercial amps are grounded, but more advanced and
transformer coupled units have floating connectors. it makes the most sense to
me to be floating, since this frees the return from line noise and spurious,
and
avoids the significant problem of shifted AC voltages on the return from
distant
units connected to the amp which are on other ac line circuits.
What is the general feeling here about this issue? I confess that if the amp
output is transformer coupled, I see exactly zero benefit in a grounded
connector as the feed from the amplifier.
Also on an unrelated topic, I found an HP 59309A HPIB clock on a forgotten
shelf
and looked at it, and was surprised to see such a poor primary time standard
oscillator inside, just a 1Mhz crystal using a cmos buffer oscillator. It can
accept an external standard, but it did feel odd for a device that is meant to
provide coordinated system time to be so modestly executed. it's like an
uncorrected PC desktop clock.
This same issue pops up in many hp/agilent counters, signal generators and
related objects. I have always been puzzled by the decision to make such
marginal instruments that have time/frequency as their primary parameter, when
so little additional effort would have dramatically improved them. I do get
the
concept of an external standard reference, but it's a pretty weak argument for
making a $5K generator or counter with poor performance. Just curious to know
everybody's thoughts on this.
all the best,
walter
--
Walter Shawlee 2, President
Sphere Research Corporation
3394 Sunnyside Rd., West Kelowna, BC
V1Z 2V4 CANADA Phone: (250) 769-1834
[email protected]
WS2: We're all in one boat, no matter how it looks to you.
Love is all you need. (John Lennon)
But, that doesn't mean other things don't come in handy. (WS2)
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