Generating Functions

Ok it's not actually generating functions, but instead a function generator.

I picked up an HP 8904A off of FleaBay because I really don't like my cheap Chinese function generator. The latter has a shitty UI, and despite having two channels it's incapable of modulating one with the other. It does have outputs on the front, though, which this one curiously lacks.

But if we peek around back, there they are.

Routing the IO on the back of an instrument is quite common in rack mounted setups where you arrange a bunch of instruments in a fixed configuration, but for more ad-hoc usage it's really a pain. Luckily, the connectors are just routed inside pretty simply with a pair of coax leads.

So it's just a matter of unscrewing them from the back and screwing them in at the front.

And of course we'll transfer the blanking plugs to the rear, though I had to heat them up with my hot air station to get the little plastic catches to stretch back into place after decades of being compressed.

But with everything back together, we get a lovely 1kHz sine wave at 1v peak-to-peak.

Which is, of course, configurable for amplitude, frequency, and so on, as are the many other wave shapes it can generate.

What we don't get, though, is modulation. You see, that's an option that you have to pay HP to enable, and whoever owned this instrument in the past never paid HP to enable it, which means the HP tech never came out and pressed the power button (on), shift, service, shift, f4, 092448, shift, service, next, next, next, f1, 3ffc, f2, ff, f4, f4, power button (off), which would have allowed the instrument to perform amplitude modulation like this.

Or frequency modulation like this.

Or many other types of more complex modulations.

What a shame, I guess I'll have to just live without.