Smallest Delay Possible in a really dumb RF communication
Latency can be estimated by the distance travelled by the speed of light of 300 m/μs with the rise time of the Rx bandwidth which may include RF and IF filters necessary to suppress adjacent carrier signals.  Where rise time = 1/3 of 1/f (f = filter Bandwidth) This requires design of simple AM Rx with no PLL.

The next delay is the AGC circuit unless a predetermined threshold for a fixed loss is defined or no AGC is used.

Latency is a tradeoff for signal selectivity or BW.