On 8/28/21 7:13 PM, AC0XU (Jim) wrote:
Thanks to all the posters. Especially to Dana - That is exactly what I was
looking for - suggestions for parts and/or circuits to do the job. I was
originally thinking that I would go with a digital circuit (sine to square to
sine), but maybe analog/sinewave would be simpler and perform about as well.
Anyway, I have ordered some of the recommended optical transceivers. We'll see
how that works out.
One or two posters mentioned that phase noise and/or thermal stability may be
issues. The referenced research papers don't seem to indicate that phase noise
is a problem. I don't think that thermal effects will be a big problem for me -
I just need to check the phase calibration from time to time. Certainly there
are expensive commerical optical clock distribution systems with excellent
properties. Maybe the devil is in the details...
My specifical application at the moment is putting several SDRs at diverse
antenna locs and feeding the IF via ethernet-converted-to-optical to my
computer. I may want to transmit at some point but receiving is all I want to
do for now. Still need a way to get a stable ref clock to each radio to provide
phase coherence.... I only need 50-60 meters but an optical solution with
single mode fibers can go many km if I ever wanted to scale up. Anyway, my plan
is to have only power carried by copper.
I don't want to go with coax, twisted pair, or any other copper solution
because of high ambient noise levels in my area and a desire to avoid adding to
it. Stringing several 100 meters of copper about my yard, carrying 10 MHz clock
signals, no matter if the cables are well shielded, doesn't seem like a great
idea.
This is totally the thing that OVRO LWA dealt with.. Not only is fiber a
LOT cheaper than coax, it solves a lot of problems.
Ethernet to fiber is really cheap ($20 for an endpoint from TP-link )
$20 from newegg
https://www.newegg.com/tp-link-mc100cm/p/N82E16833704015?item=N82E16833704015
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