Yea I have been wondering if I could use the 900Ghz with my 2.4 but I really don't know if it will work
900Ghz, that would be worse than 5.8Ghz.
Now if we are talking 900Mhz that would be more like it.
You do need to be careful that whatever you use, it is legal to do so where you are.
Also the lower the frequency the larger the antenna required.
@mountaindewdude76 I am told 1.2Ghz does not play nice with 2.4Ghz radio gear as apparently there is a harmonic that can upset your control signals.
Put it this way, you have a 1.2Ghz transmitter (video tx) in close proximity to a 2.4Ghz receiver on your aircraft, which may overpower the signal coming from your 2.4Ghz control transmitter. Result bad, very bad.