Amateur Radio RST System

Readability - Strength - Tone: RST Signal Reports

Numeric Value Readability - R Strength - S Tone - T (cw only)

1 Unreadable Faint signals, barely perceptible Sixty cycle a.c or less, very rough and broad
2 Barely readable, occasional words distinguishable Very weak signals Very rough a.c., very harsh and broad
3 Readable with considerable difficulty Weak signals Rough a.c. 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 a.c. but strongly ripple-modulated
6 Not used Good signals Filtered tone, definite trace of ripple modulation
7 Not used Moderately strong signals Near pure tone, trace of ripple modulation
8 Not used Strong signals Near perfect tone, slight trace of modulation
9 Not used Extremely strong signals Perfect tone, no trace of ripple or modulation of any kind


Select the signal's most consistent characteristic from each of the R, S, and T columns in the chart. Select the number from the R-S-T Numeric Value (left) column which corresponds to each characteristic chosen. This R-S-T sequence of numbers becomes the RST signal report.

If the signal has the characteristic stability of crystal control, the letter X may be added to the end of the RST report.

Use the letter C to indicate a chirp on the signal.

Use the letter K for key clicks.

"RST is 599" - means that the morse code cw signal being assessed is Readability 5 (perfectly readable), Strength 9 (extremely strong signal), Tone 9 (perfect tone). This is the ultimate (or "perfect") cw signal.

This reporting system may also be used for phone operation by leaving out the Tone (T) portion of the report. For example, a signal of "5 9" means that the phone signal is Readability 5, and Strength 9; a perfectly readable and extremely strong signal. The term "S-9" is also used to report a Strength 9 for an extremely strong signal. If an S-Meter is being used as a basis of the signal report, an S-9 is the notation for 9 (S-Units) on the meter.

thanx for Maxwell at buffalo edu for some information


RSQ system for Digital QSO's

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