Well that is great news, congratulations. I will be going ahead also of course, but I have to wait a few days due to a family medical issue. In the meantime it would be nice to see your before/after spreadsheet data. It is encouraging to hear that you were able to successfully complete the process. Thank you for describing your method and offering to share your data with us.
Ted,
As promised, here's a plot of my pre-cal / post-cal (for Channel 1, Channel 2 is similar) after I hacked my DG4102 to a DG4202. As you can see, it looks DANG good after the cal.
Here's a little more description of the steps I did (I didn't do things in the cleanest way, but it gave good results, so...)
1) Set cal item to AC amplitude (all measurements here are at 1kHz if I recall correctly.)
2) Go through and record each voltage value (RMS) using DM3068 and DS2202 ("DS2302"). I set each value in the DG using the DM3068 measurement.
3) Fit a line through DS2302 vs DM3068 measurements (needed to do this so that I could correct my scope measurements since it had a small offset)
4) Save and set cal item to LF flat.
5) Set each point value to the measured value on the DM3068.
6) Save and set cal item to HF flat. (DG will automatically set output to 50-ohm for this cal item.)
7) Connect a 50-ohm through terminator to the scope.
Use the corrected RMS value from the DS2302 (using the relationship in step 3) and calculate dBm. dBm=10*LOG10(Vrms^2/(50*0.001)) Record this value into the DG for each point.
9) Save and enjoy flat response from DG.
The only problem I have is that I have quite a bit of drop off when I get to low frequencies, say at 1Hz and below. (Is this normal? - Probably not. I'm redoing my channel 2 to see if this problem exists on channel 2.)
EDIT: Added channel 2 plot. Again, below 10 Hz, I'm seeing rapid fall-off (maybe something wrong with my cal method.) At 1 Hz, I've got around -4 dB (the plots start at 10 Hz, so this isn't shown.)
10 Hz and above is very flat, though.
Thanks,
Clayton