Re: RF distance
According to the free space path loss formula:
Ploss = 20*log((4*Pi*d)/Lambda)
where:
d = distance in meters
Lambda = wavelength in meters
Pi = 3.14
That means at 315 MHz the path loss at 100m is 62dB.
Assuming a 0dBd antenna gain on both sides, and ignoring other loss factors and interferers, your link budget should be ok for a proper communication using ASK.
It remains a margin of 43dB (105-62) that you can allocate for noise, error correction, interferers or whatever.
Check if your TX antenna is proper matched. There you can lose a lot of dB’s.