Ever wondered why the highest score for RSSI was 59, well the RSSI is read by using the RST (Readability Strength Tone) system.
The first number is “Readability” (1-5), Readability is a qualitative assessment of how easy or difficult it is to correctly copy the information being sent during the transmission.
Barely readable, occasional words distinguishable
Readable with considerable difficulty
Readable with practically no difficulty
And the second number is “Strength” (1-9), Strength is an assessment of how powerful the received signal is at the receiving location.
Faint—signals barely perceptible
Very weak signals
Fairly good signals
Moderately strong signals
Extremely strong signals
we recommend a RSSI value no lower than 30:
The lowest acceptable values for consistent communications.
When placing antennas attempt to position antennas so that this is the lowest level seen.