errr. how the principle works? can rigol be input with greater than 100MHz signal and read correctly?
A frequency mixer will take two signals of frequency f1 and f2 and output the sum and difference frequencies, (f1 - f2) and (f1 + f2), plus a bunch of other products like (2*f1 - f2) etc.
If your test signal f1 is 433 MHz and your local oscillator signal f2 is, for example, 432 MHz, the mixer will output a signal at (433-432) = 1 MHz as well as (433+432) = 865 MHz. Normally you would low-pass filter the output of the mixer, and maybe band-pass filter the input depending on the kind of transmitter. The 1 MHz signal would be easily visible on your oscilloscope.
You'd get away with 125 MHz into the 100 MHz Rigol, but 433 MHz would be infeasible. Attenuation aside, you'll have some nasty aliasing to contend with.