RST Code for Amateur Radio Communication

The RST code is used by amateur radio operators as well as short wave listeners to exchange information about the quality of a radio signal being received. RST stands for Readability, Strength, and Tone. The code is a three digit number with one digit each for conveying an assessment of the signal's readability, strength, and tone. The RST system is used for giving a quantitative report of the signals received. It helps to ascertain the quality of signals at the other end, which helps to improve the signal quality of the transmission.

Readability

The R stands for Readability. It is a qualitative assessment of how easy or difficult it is to correctly copy each of the characters in the text of the message sent or how easy or difficult it is for each spoken word to be understood correctly in CW and phone respectively. The readability is measured on a scale of 1 to 5.

1 - Unreadable

2 - Barely readable, only some words distinguishable

3 - Readable with considerable difficulty

4 - Readable with practically no difficulty

5 - Perfectly readable

Signal Strength

The S stands for Strength. It is an assessment of how powerful the received signal is at the receiving location. This is usually assessed by the S-meter of the radio receiver in a location. The Strength is measured on a scale of 1 to 9.

1 - Faint signal, barely audible

2 - Very weak signals

3 - Weak signals

4 - Fair signals

5 - Fairly good signals

6 - Good signals

7 - Moderately strong signals

8 - Strong signals

9 - Extremely strong signals

Tone

The T stands for Tone. Tone is used only used in CW or Morse code and in digital transmissions. It is omitted during voice operations. The imperfections in tone in digital transmissions are not usually detected by humans as it is ascertained by the receiver itself. If the CW signal is steady because of crystal control, add X to the report eg. RST 599X. If the signal chirps, add C to the report eg. RST 567C. If the signal has key clicks, add K to the report eg. RST 588K. Tone is measured on a scale of 1 to 9.

1 - Very rough and broad a.c., sixty cycle a.c. or less

2 - Very rough a.c., very harsh and broad

3 - Rough a.c. tone, rectified but not filtered

4 - Rough tone, some trace of filtering

5 - Filtered rectified a.c. but strongly ripple-modulated

6 - Filtered tone, definite trace of ripple modulation

7 - Near pure tone, trace of ripple modulation

8 - Near perfect tone, slight trace of modulation

9 - Perfect tone, no trace of ripple or modulation of any kind