The RST Signal Reporting System

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The RST system is a code widely used in amateur radio to briefly and concisely describe the quality of a received radio signal. It is used particularly often in modes like Morse code (CW) and digital modes, but can also serve as a reference for voice transmissions. RST stands for:

  • Readability
  • Strength
  • Tone (primarily for CW)

An RST report consists of three digits, e.g., "599". Each digit represents an evaluation on a scale.

R = Readability

Readability indicates how easy or difficult it is to understand or copy the transmitted information.

  • 1: Unreadable
  • 2: Barely readable, occasional words distinguishable
  • 3: Readable with considerable difficulty
  • 4: Readable with practically no difficulty
  • 5: Perfectly readable

S = Strength

Signal strength describes how strong the received signal is. Many radios have an S-meter that provides an indication, but the RST report should primarily refer to the heard signal, not just the meter reading.

  • 1: Faint signal, barely perceptible
  • 2: Very weak signal
  • 3: Weak signal
  • 4: Fair signal
  • 5: Fairly good signal
  • 6: Good signal
  • 7: Moderately strong signal
  • 8: Strong signal
  • 9: Extremely strong signal

T = Tone

The Tone value specifically refers to the quality of the CW signal (Morse code tone). For voice transmissions (Phone), this part is often omitted or replaced with a verbal description.

  • 1: Extremely rough AC note, harsh and broad
  • 2: Very rough AC note, no trace of musicality
  • 3: Rough low-pitched AC note, slightly musical
  • 4: Rather rough AC note, moderately musical
  • 5: Musically modulated note
  • 6: Modulated note, slight trace of whistle
  • 7: Near DC note, smooth ripple
  • 8: Good DC note, just a trace of ripple
  • 9: Perfectly pure DC note

Important Note on Tone (T): With modern radio technology, tones below T9 have become rare today. A value below 9 often indicates problems with the transmitter (e.g., "chirp").

Optional Suffixes

Sometimes letters are added to the RST code to provide additional information:

  • X: Stable frequency, crystal-controlled quality (less common today as most transmitters are stable).
  • C: "Chirp" - frequency drift during keying. Example: 579C.
  • K: "Key clicks" - unwanted clicking sounds during keying. Example: 599K.

Examples of Reports

  • 599: Perfectly readable, extremely strong signal, perfect tone (the most common report, sometimes unfortunately given even when not entirely accurate).
  • 579: Perfectly readable, moderately strong signal, perfect tone.
  • 338: Readable with considerable difficulty, weak signal, good tone with slight traces of ripple.
  • 599C: Perfectly readable, extremely strong, but the tone has an audible chirp.

Honesty Counts!

Although "599" is the most frequently given report, it is important to give an honest report. A realistic RST helps the other station assess their antenna, power, or settings. If you have difficulty reading the signal, a "339" is more honest and useful than a sugar-coated "599".

Conclusion

The RST system is a simple yet effective tool for quickly evaluating signals in amateur radio. Understanding and applying it correctly is an important part of good operating practice, especially in CW operation.