Hi The gotcha with transformer coupled coax is keeping it terminated over a wide range of frequencies. If the coax is miss terminated and the end of the cable is floating, you have a pretty good opportunity for noise to get into the system. Floating shields are also a pretty good way to get crosstalk. In many situations, isolation between outputs is a pretty big deal.
Bob > On Jan 28, 2017, at 12:29 PM, walter shawlee 2 <walt...@sphere.bc.ca> wrote: > > 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 > walt...@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) > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
