How about something like this?
A few things I don't know about:
the output pad messes up the output impedance–I'm not sure this is a problem, but if it is, I'll change it to an H pad.
the smallest resistor in the output pad is tiny, 1.2R. I'm planning to use slide switches to keep the cost reasonable. Even with the contact resistance of the switch, the pad should still be accurate within a couple of dB–is this likely good enough, or would it be a better idea to bump up the total resistance of the pad?
This schematic is becoming a bit of a maze. Once everything is more or less as it should be, I'll draw it again for easier reading.
The big news: I picked up my QA400 from the post office today and tried to get it up and running. The computer I'm using it with runs Windows XP SP3. The software and drivers installed without incident. However, the calibration procedure keeps failing. When I try loop-back measurements with the uncalibrated device, the plots look feasible and it seems to be working as it should, but for some reason it won't calibrate; at first, the program crashed, but now the calibration window just spits out a cryptic error message. I'm exchanging emails with the Quantasylum support, and they've been helpful so far. But, we haven't found the solution yet.
It's possible something is just going wrong because I'm using an old computer, but I have no clue. Hopefully I'll know more about this soon.
A few things I don't know about:
the output pad messes up the output impedance–I'm not sure this is a problem, but if it is, I'll change it to an H pad.
the smallest resistor in the output pad is tiny, 1.2R. I'm planning to use slide switches to keep the cost reasonable. Even with the contact resistance of the switch, the pad should still be accurate within a couple of dB–is this likely good enough, or would it be a better idea to bump up the total resistance of the pad?
This schematic is becoming a bit of a maze. Once everything is more or less as it should be, I'll draw it again for easier reading.
The big news: I picked up my QA400 from the post office today and tried to get it up and running. The computer I'm using it with runs Windows XP SP3. The software and drivers installed without incident. However, the calibration procedure keeps failing. When I try loop-back measurements with the uncalibrated device, the plots look feasible and it seems to be working as it should, but for some reason it won't calibrate; at first, the program crashed, but now the calibration window just spits out a cryptic error message. I'm exchanging emails with the Quantasylum support, and they've been helpful so far. But, we haven't found the solution yet.
It's possible something is just going wrong because I'm using an old computer, but I have no clue. Hopefully I'll know more about this soon.