Readability - Strength - Tone:   RST Signal Reports
T (cw)
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 N/A Good signals Filtered tone, definite trace of ripple modulation
7 N/A Moderately strong signals Near pure tone, trace of ripple modulation
8 N/A Strong signals Near perfect tone, slight trace of modulation
9 N/A Extremely strong signals Perfect tone, no trace of ripple or modulation of any kind



Select the signal's most prominent characteristic from each of the R, S, and T columns in the chart. Select the number from the R-S-T Numeral (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 the letter C to indicate a chirp on the signal and 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 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 numeric level of 9 (S-Units) on the meter.