Cheap UHF spectrum analyzer (and RC tx rx) using RFM22 module

just few questions to clarify if what im seing is correct.
below is a picture of a test running currently running on the bench.

if you look at the picture with only the RF22 switched on that is working as the receiver it would appear that there is a very high signal detected in the UHF range where i stay ? or am I seing it wrong ?

also the labeling of the dBs on the left hand side would it not make more sence if it started form -120 at the top and -20 at the bottom? I arleady made the mistake at looking at the spike but in reality if i understand it correct is actually the lowest detected frequency that im looking at , can it be swapped ?

other question is , I have a 17cm antenna on my receiver this would offcourse make a differences for freq. in the 800 or 900 range . what then ? or is this meant to be used with Rf probes only and not general area scanning ?

thanx for any advice , really keen on useing this more