R-S-T Codes
When a radio operator makes contact with another station the most basic exchanges that are made are Callsign, Operator Name, Signal Strength and Voice Quality. For the latter two we use the R-S-T system.
R - Readability
S - Signal Strength
T - Tone
Within this system the R will indicate how well the other station can understand the transmitted audio. This ranges on a scale of 1-5, with 1 being 'unreadable' and 5 being 'perfectly readable'. There are many factors that can affect the readability: atmospheric noise, static crashes, signal fading, and man made noise being some of them.
The S in the report is the strength of the signal. This is important to the transmitting station as it will give a clear understanding of how well the operator has set up their 'shack'. Is the antenna tuned and working correctly? Is the coax performing as it should? And is the radio transmitting at the power that is expected? The signal strength is 1-9 with 1 being a 'faint signal, barely perceptible', and a signal strength of 9 is an 'extremely strong signal.'
The third number refers to Tone and applies to CW (Morse Code).
Below is a table with the respective numbers:
| Numeric Value |
R - Readability | S - Signal Strength | T - Tone (CW Only) |
|---|---|---|---|
| 1 | Unreadable | Faint Signals, Barely Perceptable |
Sixty Cycle AC or Less, Very Rough and Broad |
| 2 | Barely Readable, Only Occasional Words Distinguishable |
Very Weak Signals | Very Rough AC, Very Harsh and Broad |
| 3 | Readable with Considerable Difficulty | Weak Signals | Rough AC Tone, Rectified but Not Filtered |
| 4 | Readable with Practically No Difficulty | Fair Signals | Rough Note, Some Trace of Filtering |
| 5 | Perfectly Readable | Fairly Good Signals | Filtered Rectified AC but Strong Ripple-Modulated |
| 6 | - | Good Signals | Filtered Tone, Definite Trace of Ripple Modulation |
| 7 | - | Moderately Strong Signals | Near Pure Tone, Trace of Ripple Modulation |
| 8 | - | Strong Signals | Near Perfect Tone, Slight Trace of Modulation |
| 9 | - | Extremely Strong Signals | Perfect Tone, No Trace of Ripple or Modulation of Any Kind |