[time-nuts] WWVB phase modulation test April 15-16
hmurray at megapathdsl.net
Thu Apr 12 03:56:23 EDT 2012
> Just the T and a DC block. 1/4 wave at 60 kHz is far, far longer than any
> cable you have.
This is time-nuts. Somebody is likely to do something most of us would
consider, well, nutty.
It's probably reasonable to make a lumped-circuit approximation of a long
transmission line at 60 KHz or 100 KHz.
Many years ago, when we were working on early 10 Mb Ethernet, a friend rigged
up a good approximation to a long chunk of coax with 1 R and 1 C and a few
clip leads. It looked pretty good on a scope.
I ordered several 500 ft spools of coax so we could test the real thing. 500
ft of Ethernet coax (not thinwire) is a serious spool. A key step was
getting the maintainance guy to build a dolly with serious casters. He was
happy to do something strange. The result was slight overkill which is what
I wanted. It worked great. Every lab should have one. :)
How many of you have used the Tek scope-probe to BNC adapter? I tried a bit
but couldn't find anything on the web. The idea was (roughly) that you put a
BNC Tee in the line you wanted to watch and this magic gizmo on the Tee. One
end was BNC. The other end was a hole where you inserted a scope probe. The
idea was to avoid the inductance on the pigtail for the ground cliplead.
Not quite so many years ago, we built a SONET/OC-3 delay box. It was just a
fiber optic receiver, FPGA, knobs, memory, and fiber optic transmitter. The
FPGA could just barely run at 155 megabits. We used a recycled memory
module. I think it was 36 bits wide with 1 megabit chips. The idea was to
let the software guys test long links in their lab. It worked great. (I
think that size memory covered (roughly) California to Paris.)
These are my opinions, not necessarily my employer's. I hate spam.
More information about the time-nuts