[time-nuts] WWVB phase modulation test April 15-16
Hal Murray
hmurray at megapathdsl.net
Thu Apr 12 07:56:23 UTC 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.
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