[time-nuts] distribution amp question + hp 59309A

walter shawlee 2 walter2 at sphere.bc.ca
Sat Jan 28 12:29:13 EST 2017

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 Shawlee 2, President
Sphere Research Corporation
3394 Sunnyside Rd.,  West Kelowna,  BC
V1Z 2V4  CANADA  Phone: (250) 769-1834
walter2 at sphere.bc.ca
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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