[time-nuts] Frequency distribution isolation transformers YCL 20F001n arrived

[ed breya]

I investigated those 10b-t isolation modules a while back, and have 
saved every module from every network card and router/hub/switch that 
I have junked out. The very old 10b-t stuff is the best for getting 
LPFs and individual per-channel (port) type parts. When they started 
making 10/100 Mb/sec, the 17 MHz filters were eliminated, and the 
parts got integrated to ever-higher levels, with multiple channels in 
each module.

You have to be able to find the data sheets to be sure of what's in 
them - some are transformers only, and some also have LPFs and 
common-mode chokes in various combinations. The filter sections can 
also be cascaded for even sharper cutoff, but there's quite a bit of 
crosstalk, so a lot of higher frequency stuff gets through, 
especially above 100 MHz, so it's mostly effective from around 20-100 
MHz. It has been mentioned before that very sharp filters will tend 
to have more phase noise (phase shift with temperature/component 
variations), but the negative effects depend on the application - I 
only care about frequency reference distribution to SAs and 
synthesizers, for example, so I don't worry about exact phase and 
timing between equipment.

There is a nice variety of magnetic parts from all types of network 
devices, including DSL an ISDN.

Ed