@Johnny B Good. Thank you for your generous input. Your knowledge of OCXOs and GPS is way ahead of me. I am a novice here so am happy to take baby steps for the time being. That is why I was attracted to the apparent simplicity of @AndrewBNC's GPSDO. If I can get this to work, it may lead to other similar projects - who knows?
I was pretty much in that position about four and a half years back myself with regard to ocxos and gpsdos. You'd be surprised as to where even a vague fascination in "Electronics" (to give the subject its generic all encompassing label) will lead you to these days.
I started with a one valve (vacuum tube) radio kit based on the DK91 (90v HT and 1.5v heater) that had been donated/sold to my dad by one of his workmates (probably an unwanted gift) when I think I must have only been 11 or 12 years old way back in the early sixties. As to whether I managed to get it working is now lost in the mists of time.
However my one abiding memory of what had sparked off my interest in electronics is of a "child safe" 3 volt powered transistor based multiproject electronics kit I'd received as a Christmas present shortly thereafter which was based on a hardboard pegboard which used schematic overlay sheets with holes matching the pegs on the plastic mountings onto which the components had been soldered to spring clips allowing solderless assembly (an early form of plug in solderless breadboard if you will). ISTR it having 7 such schematic overlays all of which I tried out, inventing a few extra variations of my own into the bargain, mostly in the (fascinating to me) subject of wireless communication.
Afterwards, I gained an (one might say unhealthy) interest in the technical section of my local library on the subject of electronics, specifically, transistor based material (well, there was much less risk of electrocution than that inherent in the more classic thermionic valve based technology). From then on, I was doomed to a lifelong interest in the rapidly evolving subject of electronics (audio amps opamps, simple logic, hybrid valve/transistor MF transmitters, audio magnetic tape technology, microprocessors (of the Z80 kind) and so on. I won't go into any more detail since this almost certainly echoes the experience of many, if not most of this forum's membership.
Suffice to say that, despite my lifelong experience, I'd still had something new to learn when I strayed into this particular rabbit hole of metrology. I too had to take 'baby steps' when I moved onto upgrading the crappy 50MHz smd oscillator in my much modified Feeltech FY6600 arbitrary wave generator to a 50MHz 0,1ppm tcxo board that had been my first step onto this particular road to 'metrology madness' (the second step being the upgrade to an ocxo that I could frequency inject stabilise to an external 10MHz reference), followed of course, by an inevitable search for 'perfection' in the form of building gpsdos and purchasing a couple of rubidium oscillators.
![Face Palm :palm:](https://www.eevblog.com/forum/Smileys/default/facepalm.gif)
You can take this relatively short (by my standards) missive as a hint as to what you may be letting yourself in for with this recently acquired interest in this project. Don't say you haven't been warned.