@Gordon Nichols, Agreed, MOSFETs are versatile! I had nursed an old tube based analog HP scope from my early twenties until it just couldn't keep up with computer timing speeds. I felt like a super geek when my dear wife bought me a digital USB scope for my laptop. I've had it nearly 10 years and have no complaints. It's been superseded by the manufacturer with this scope:
https://www.amazon.com/Hantek-...DCFBMGEPJ5MJMVB6QMQ5
I like the idea of a phone connected scope but always worry about the rapid changes in connectors for phones.