[time-nuts] Re: Query about List and about 10 MHz Distro

[Anders Wallin]

FWIW we've played with various SMA-to-SFP converter boards in the lab for
10MHz or 100MHz distribution.

A bare-bones SFP board is e.g.
https://github.com/aewallin/SFP-Breakout-Board
That interfaces directly to the differential AC-coupled TX and RX pins of
an SFP.

If you want some buffering (and limited bandwidth at the same time) you can
put an op-amp as a buffer and a transformer to convert to/from the
differential TX/RX.
Here's a design I've used https://github.com/aewallin/SFP2SMA_2018.03
We also made a box around that board:
http://www.anderswallin.net/2020/12/sfp-board-in-a-box/

If your requirements are somewhere in 1e-14 or worse then this type of
passive frequency distribution should work fine for maybe a few km fiber
runs.

Anders


On Mon, Aug 30, 2021 at 8:13 AM Poul-Henning Kamp <phk at phk.freebsd.dk>
wrote:

> --------
> David I. Emery writes:
> > On Sun, Aug 29, 2021 at 10:43:51AM -0400, paul swed wrote:
>
> > Not completely clear what the common
> > mode  Z of the things is at 10 MHz...
>
> Twisted pair is 135 Ohm.
>
> --
> Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
> phk at FreeBSD.ORG         | TCP/IP since RFC 956
> FreeBSD committer       | BSD since 4.3-tahoe
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