Ham Radio RST Signal Report System Reference
The RST system is the standard way amateur radio operators report signal quality to each other. RST stands for Readability, Strength, and Tone. Every ham radio operator needs to understand this system to give and receive meaningful signal reports during contacts on any mode.
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Readability describes how easy it is to understand the complete message, not just whether you can hear the signal. A strong but heavily accented or badly distorted signal might only be R3 even though the S-meter reads 9.
| R | Description | What it means in practice |
|---|---|---|
| 1 | Unreadable | Cannot copy any part of the transmission |
| 2 | Barely readable | Occasional words distinguishable |
| 3 | Readable with difficulty | Copy possible but significant concentration required |
| 4 | Readable with no difficulty | All words understood, some effort needed |
| 5 | Perfectly readable | Every word is completely clear with no effort |
Signal strength corresponds to the S-meter reading on your receiver. S9 is the reference level defined as 50 microvolts at the antenna input on HF, or 5 microvolts on VHF. Each S-unit represents 6 dB of signal change, so S9 is 48 dB stronger than S1.
| S | Description | Approx. dBm (HF) |
|---|---|---|
| 1 | Faint, barely perceptible | -121 dBm |
| 2 | Very weak | -115 dBm |
| 3 | Weak | -109 dBm |
| 4 | Fair | -103 dBm |
| 5 | Fairly good | -97 dBm |
| 6 | Good | -91 dBm |
| 7 | Moderately strong | -85 dBm |
| 8 | Strong | -79 dBm |
| 9 | Extremely strong | -73 dBm |
Signals above S9 are reported as S9 plus the number of dB over: S9+10, S9+20, S9+40 and so on. A "full quieting" VHF FM signal that completely suppresses receiver noise is sometimes reported as S9+60 or simply "full quieting."
Tone — T (1 to 9, CW only)The tone number applies only to CW (Morse code) contacts and describes the quality of the transmitted carrier. A perfect DC-keyed signal produces a pure sine wave tone rated T9. Older transmitters using AC-derived power or poor filtering produce rough, buzzy tones rated lower. On phone and digital modes, only R and S are used, giving a two-digit report.
| T | Description | Cause |
|---|---|---|
| 1 | Extremely rough, AC note | Unfiltered AC, very old equipment |
| 2 | Very rough AC note | Poor filtering, heavy ripple |
| 3 | Rough, low pitch AC note | Some filtering but significant ripple |
| 4 | Rather rough AC note | Moderate ripple present |
| 5 | Filtered tone, some ripple | Reasonable filtering |
| 6 | Filtered tone, slight ripple | Good filtering, minor imperfection |
| 7 | Near pure DC tone, slight trace | Very good filtering |
| 8 | Near perfect tone, slight hum | Excellent equipment, minor issue |
| 9 | Perfect DC tone | Ideal CW signal, no detectable imperfection |
Phone (SSB, FM, AM)
Use a two-digit RS report only. The tone number does not apply to voice modes. A typical phone report sounds like: "You are five and nine" or "Your report is 59."
CW / Morse Code
Use the full three-digit RST report. A perfect CW signal is 599. In contests, 599 is sent as 5NN using the CW abbreviation for 9 (N = dah-dit = 9 in some contest shorthand).
Digital Modes (FT8, JS8, PSK31)
FT8 and WSPR use their own SNR-based reporting in dB. Other digital modes like PSK31 commonly use 599 as a courtesy report regardless of actual signal quality, since the software decodes the signal automatically.
SSTV and Image Modes
SSTV uses a modified report: RSV where V is video quality from 1 to 5. The standard RS report is still used for the audio carrier quality.
In practice, most contacts on a clear frequency result in good signals and the same handful of reports are heard repeatedly. Here are the most common ones and what they really mean:
One of the persistent habits in amateur radio is giving an automatic "59" or "599" to every station regardless of actual signal quality. This "courtesy report" is particularly common in contests where speed matters more than accuracy, and on digital modes where the software does the decoding.
Outside of contests, an honest signal report is far more useful. If someone's signal is really a 57, telling them so helps them know their antenna is working, or conversely, that they have a problem to investigate. A string of honest 44 reports might prompt an operator to check their feedline or antenna connections. Honest reports make the hobby more useful for everyone.
The exception is when a station is running a specific antenna test or comparison — in that case they will explicitly ask for honest reports and appreciate them.
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