Or option C? I'm spitballing a bit, but it looks like an absolutely-correct antenna for your clock might be a Symmetricom 140-615. There's a couple (literally

Or option C? I'm spitballing a bit, but it looks like an absolutely-correct antenna for your clock might be a Symmetricom 140-615. There's a couple (literally two) on the ebay right now that look minty-fresh; they're not the cheapest things, but they're cheap compared to many other things in the low-volume RF world. :) If that's the right antenna (just because I think it is doesn't mean that you should agree), then that would certainly simplify the RF side of the project. No hardware mods required at all. It takes 12v and does internal downconversion to the right frequencies. After that, you only have the daunting task of patching firmware -- if it turns out (from testing) that it patching is even required. (IIRC, you speculated in the video that it might already be patched and I don't disagree with that outlook at all.) Both legs of this thing represent interesting projects. I find that time is strangely rewarding to get exactly-right even when that doesn't really matter for the application at-hand. It's a good kind of weird. (I really need to fire up my own little GPS-sourced Pi Zero NTP server some day soon. Chasing temperature-based clock deviations on that was actually kind of fun.)