Just today I have managed a small checkup of my brand-new DSO Quad, testing it with some signals and a pro scope.
Well, I have connected a HP signal generator 0 dbm (sine wave approx 0.5Vpp) on a 50 Ohms load, together with the Quad (ch-A) and a LeCroy scope (5GHz bandwidth).
So far so well, the first test is with frequency 1.0 MHz: clearly quite far from the 72 MHz analog bandwidth declared for the Quad.
The wave is well reproduced, having almost the same amplitude (no noticeable failures).
The first problem: by setting the trigger to AUTO (ch-A), the waveform displayed is totally wrong. It is not a sine wave but somewhat cut randomly: it is a clear firmware problem, I guess.
OK, never mind, let’s use the trigger set to NORM (rising slope).
Second problem, using a time/div under 1uS often the waveform freezes. I must turn off and on again to restore the activity.
However, during this situation the menus/switches are working fine (I can navigate, but the wave does not care about what I do).
I never noticed by using time/divs above 1 ms. I don’t know using from 1us to 1ms.
The second test wanted to measure the frequency at 10 MHz, even far from the 72 MHz.
One the LeCroy scope the signal is 10 MHz still showing the same amplitude of 0.5 Vpp (0dbm).
On the Quad the waveform is almost a straight line.
So I have tried to start from 1 MHz back, then step 1 MHz at time…just at 2 MHz the sine amplitude showed on the Quad is about 75% of the actual, that is -3 dB of bandwidth.
Over the problems above, my question is: how did you measured that 72 MHz of bandwidth?..As my test, I have detected just 2 MHz!