Thanks
I will own the fact that I didn't read every line of the DG900 datasheet I quote below in a jpeg attachment
(not sure how to make it inline). I think you could see why after viewing the imaged snippet that I was satisfied that I
could use the modulation feature at 100 kHz. There were duplicate sets of lines after that referencing Internal/External
and a 1 MHz BW over and over, and I had already read something about the input impedance in another place. I had
seen what I was looking for already and didn't find my way down to the "catch" where they say the BW is 50 kHz. I'm
not sure that I would like the results of modulation at 50 kHz either but at the end of the day I would agree that the
fault is mine. Caveat Emptor.
About the sampling, here is the content of the current advertisement on Amazon:
100MHz Function Generator, 2 Channel, 250MSa/sec, 16Bit Resolution, 16M Memory
100 MHz function / arbitrary waveform generator
16 Mpts memory depth per channel for arbitrary waveforms
and here is what is at the top of the data sheet mentioned by thm_w:
----------------------------------------------------------------------------------------
Unique SiFi II (Signal Fidelity II) technology: generate the arbitrary
waveforms point by point; recover the signal without distortion; sample
rate accurate and adjustable; jitter of all the output waveforms (including
Sine, Pulse, etc.) as low as 200 ps
16 Mpts memory depth per channel for arbitrary waveforms
Standard dual-channel with the same performance, equivalent to two
independent signal sources
...
Sample rate up to 250 MSa/s, vertical resolution 16 bits
Arbitrary waveform sequence editing function available; arbitrary
waveforms also can be generated through the PC software
--------------------------------------------------------------------------------------
I don't remember, but I must have read the material below that and perhaps
wondered what they meant by:
Basic Waveforms Sine, Square, Ramp, Pulse, Noise, DC, Dual-tone
Advanced Waveforms PRBS, RS232, Sequence
Built-in Arbitrary Waveforms 160 types of waveforms, including Sinc, Exponential Rise, Exponential Fall, ECG, Gauss, HaverSine,
Lorentz, etc.
.....
Sequence 2 k to 60 MSa/s
Noise (-3 dB) 100 MHz bandwidth
Arbitrary Waveform 1 μHz to 15 MHz 1 μHz to 20 MHz 1 μHz to 20 MHz
It looked like what they meant by ARB waveform was their collection of functions so I chose, perhaps correctly,
to connect the 20 MHz limit with those things, believing that they referred to a limit for playing out predetermined
lists of points. And that may not be wrong.
What I should have understood is that, by their terminology what I was doing was an "Advanced" "Sequence"
to which the limit 2 k to 60 MSa/s applies.
Well, all right.
In the end, I made a generous interpretation based on the headlines and what I wanted it to be. I didn't call them
because it was likely to be a waste of time. Very few companies anymore let you talk to people who aren't reading
canned scripts. I have bought exactly two pieces of Rigol gear and was very favorably impressed with their capabilities
so this time when the item provided less value than I expected rather than more it made me unhappy.
Unfortunately I didn't know that there was a big thread about this unit before I bought it and I think reading that might
have stayed my hand. I am not a regular reader of EEVBLOG, shame on me!