I've looked at doing this a few times. I don't have references handy but there are cheaper atomic oscillators available now, under $1000. Still to expensive for me to justify it but one of these years I'll find one cheap.
A signal distribution box used from eBay is a lot cheaper than a good outdoor GPS antenna!
Though if you have enough cable and enough antennas already, no harm in having a little array like in OP.
Too bad you couldn't hack the Americium module from a smoke detector and create a DIY atomic oscillator. Cesium seems to be preferred. (And I know nothing about this sort of thing.)
(EDIT: chatting with an LLM… I realize I had assumed that "atomic clocks" meant radioactive and so suggested Americium because it is easy to obtain. LLM schooled me and suggested "Rubidium oscillator modules" instead since they come up for a few hundred dollars or so on eBay. Still not the DIY approach I had hoped for—I think I am still channelling the old "Amateur Scientist" column from Scientific American from the day.)
And Americium is not as useful for a timing reference, as it's not as stable as Rubidium and a lot less safe to handle. Otherwise time nuts would hoard cheap smoke detectors :)
So now you have me going to eBay in search one but all it turns up are BM25CSAC carburetors! What are the magic keywords to use in my search?
The photo of the device on the article says "Jackson Labs" which seems to have been the previous name of "Viavi Solutions" and a review video [2] mentioned using Symmetricom atomic clock modules, which was acquired first by Microsemi (2013) and subsequently Microchip (2018)[3].
[1] https://www.viavisolutions.com/en-us/products/chip-scale-ato...
