Unless I'm missing something, this doesn't have a 50ohm output. The voltage only lines up with the scope on a 1M input impedance.

No. I measured the output impedance, it has pretty precise 50 Ohm impedance for all voltage ranges up to 6 Vpp.

I didn't measured output impedance for amplitudes above 6 Vpp, because I'm worry about my RF dummy loads (because they are low power and may be burned out from high power

). But I think it's output impedance the same 50 Ohm up to 25 Vpp.

If you're talking about display value, yes it always displays open output amplitude for internal 50 Ohm impedance. So, you're needs to recalculate it for your load. Since PSG9080 hardware output is 50 Ohm, for 50 Ohm load you can just divide displayed value by 2 to get Vpp (peak-to-peak) amplitude on the load. Or divide displayed value by 4 to get Vpk (peak) amplitude on the load.

Since it displays amplitude for open output, you're needs to apply correction factor for displayed amplitude in order to get Vpp value on specific load:

- for 50 Ohm load Vpp = displayed Vpp * 0.5

- for 75 Ohm load Vpp = displayed Vpp * 0.6

- for 600 Ohm load Vpp = displayed Vpp * 0.923077

- for 1 MOhm load Vpp = displayed Vpp * 0.99995

- for 10 MOhm load Vpp = displayed Vpp * 0.999995

You can look my output impedance measurements

here. It is performed with Siglent SDS1102X oscilloscope. With taking into account oscilloscope measurement error, we can see that PSG9080 has pretty precise output impedance 50 Ohm.

PS: just tested impedance with multimeter Brymen BM867:

500 Hz square wave, 1.000 Vpp setting on the generator.

10 MOhm input = 499.76 mV RMS

49.80975 Ohm input (10 MOhm in parallel with [49.77 Ohm + 0.04 Ohm wires]) = 249.20 mV RMS

Calculated output impedance = 50.08 Ohm