I connected a rf signal generator to the PSCU1000, freq set to 7 Mhz, set level to 500 mv peak and I see see many peaks to the right of the fundamental, I am assuming that the first peak is the second harmonic, and if it is, it's freq should be about 14 Mhz.
You must use the oscilloscope display to see that there is no clipping of the waveform. The waveform should look nice sine wave on the oscilloscope screen.
From your screen shot, you marked the second peak from the fundamental and if I am reading it right, it is 62.81 db down from the fundamental peak level. Is there a reason why you did not use the first peak instead of the second?
I selected the second peak just as an example to show how you can use the markers (cursors) on the screen to make measurements. You can freely move the marker lines by the mouse and measure the other peaks displayed, e.g. the first or the second harmonic.
I have a couple of more questions to asked, what does f21.10 Mhz at the base line represent?
It is the frequency of the position of the vertical marker on the screen.
how do I determine the freq's of the fundamental and harmonics by looking at the display?
Just move the vertical marker using the mouse. You'll see the frequency at the base line.
and finally what does setting the freq range to 25 Mhz accomplish?
It is the displayed frequency range on the screen.