Digital oscilloscope

[Mike Watterson]

Just realised that I forgot my usual pithy line:

Digital 'scopes complement analogue 'scopes, not replace them.

Personally, I'd hate to only have a digital 'scope.

Indeed X -Y mode doesn't work on cheap ones.
Cheap ones have a useless input attenuator and poor trigger control
You'd want nearly 1GHz sample rate to be as useful as a dual channel 20MHz scope, which certainly will show signals, but at rubbish accuracy to nearly 100MHz if a Tek, not so much if a Hameg. Divide quoted sample rate, not by 2 for Nyquist limit, but by 10, so you know if it's not a sinewave! Divide again by number of channels.

A decent Digital scope to replace a good 100 MHz analogue one might be the price of a car. One of my sons has digital "scope" they bought "ex demo" so as to look at HDMI galvanic isolator performance. A big multinational. Of course it does stuff an ordinary digital scope or analogue one can't do.

I'd sooner have 100MHz Tek analogue scope than a digital one, but both would be nice as long as it was a "real" digital scope. Meanwhile I have the 20MHz Hameg, a Dual IF Meguro Geniscope (Analogue sweep 460 kHz and 10.7MHz IF) and an HP141T spectrum analyser with three different RF plugins. If the storage tube dies, it's possible to drive a regular scope at normal sweep rates and a sound card at slow sweeps or dumb plotter at very slow sweeps.

I don't have the companion tracking generator for the HP141T, though maybe my DDS based sig gen can. I made a wide band noise source with a wide band power amp to drive filters etc and see response on the HP141.