IF Output question
Not sure if this is a good place for this question (I don’t post on Reddit much, but read here often). In the process of getting my general again.
I have an old SDR receiver that was given to me by an RF engineer at a previous job. It’s an AOR SR2200. It doesn’t have an I/Q output but does have an IF Out at 10.7MHz. I recently picked up a tinySA ultra and connected the IF Out to it. I tuned into local broadcast FM stations to see if I could make sense of it. I was surprised to find that the displayed spectrum was reversed. Meaning the high frequency stations (106.5) showed up on the low end of the displayed spectrum and low frequency stations showed up on the high end of the spectrum. When I tune the receiver to, say 106.5, it shows up on the TinySA at the IF frequency of 10.7 which makes sense to me.
My question is why is the spectrum reversed? I expected to tune up and listen to a higher frequency station, but that was not the case.