The good news is that I can finally measure the fast and/or short pulses I've been working to make. The bad news is that they're not what they should be. The laser-driver pulse generator from a few logs ago measures out around 150 ps fall time. It should be much less than this - less than 40 ps, ideally. I haven't managed to measure the rise time yet.

There could be any number of reasons for this, including my use of inexpensive - and physically large - passive components instead of high-frequency types. My PCB design probably doesn't help. There's a list of rise-times of various connectors and cables in the "black magic" book - I should add up the contributions from all the junk I have in the signal path, too.

There is also a lot of jitter - I'm not actually sure I'm seeing the edge associated with the trigger here. If it were some later edge, that might explain much of the jitter.

It's a little disappointing that the thing didn't "just work," but still exciting that I can see what's going on and iterate until it works.

The machine behind the new measurements is this Tektronix 11801B with four SD-24 sampling heads. It arrived today from ebay, and I just finished a first test - all eight 20 GHz channels seem to work fine. The thing is a 60-pound monster, and I'm going to need to find something to put it on, because it takes up half my bench.

I was in college around 1990 when this was new. It sold for around the same price as my entire education. We are so amazingly lucky to live in the time of ebay.