Sensitive VHF reciever/scanner under 200$?

Hi, I am not sure if this is the right section to post this so pardon me if this was wrong. I am working in a lab and making a series of experiments inside and outside buildings. I want to pick up various very weak signals at specific frequencies above 100mhz. NOTE: I am going to connect the receiver to a spectrum analyzer to analyse the transmission carrier wave itself. I wonder if you could help me pick the best one for the job under 200$ , that would be really appreciated



Requirements:

-detect very weak signals in the range around between 100mhz to 200mhz(higher than 200mhz is fine ofcourse too)

- high sensitivity/ good signal to noise ratio

- selectivity:very narrow bandwidth if possible



I read amplifying nowadays is not a problem and that you could install various antennas and preamps etc. But the most crucial thing is the sensitivity and signal to noise ratio if I understand correctly. So sensitivity is a priority I guess to pick weak signals?

I searched the net and ebay and there is a plethora of instruments, there are all from modified usb dongles, unknown unmarked smaller boxes without specifications on ebay, to handheld wideband small scanners, and stationary wideband receivers and scanners.



Which should I look for?

What is the best bang for buck to fulfill my requirements above do you think?

thx

Karl