What I want to do is measure the bandwidth of a wireless video transmitter. I know for a fact that this is going to be at least 8 MHz if not much more as it gives a good video image with an OSD which has a pixel clock exceeding 4 MHz. (I'm trying to repurpose the transmitter to send other analog data.) Since I have no access to a high frequency signal generator (10 MHz+) to directly verify the -3dB point, is it possible to measure, say, the -1dB point and derive the frequency of the -3dB point from this?
Electronic – measure the -3dB point of a wireless link with a lower frequency
frequency
Best Answer
Assuming your transmitter is NTSC, you have 4.2MHz to play with, according to Wikipedia.
To answer the original question, yes, it is possible to measure a signal at a lower frequency (using aliasing), but you must be able to sample at atleast twice the bandwidth of interest, and the signal band must start at a multiple of your sampling rate.