Ham Radio "RST" Signal Reporting System for CW/Phone Operation

Readability - Strength - Tone:   RST Signal Reports
Numeric Value
T (cw only)
1UnreadableFaint signals, barely perceptibleSixty cycle a.c or less, very rough and broad
2Barely readable, occasional words distinguishableVery weak signalsVery rough a.c., very harsh and broad
3Readable with considerable difficultyWeak signalsRough a.c. tone, rectified but not filtered
4Readable with practically no difficultyFair signalsRough note, some trace of filtering
5Perfectly readableFairly good signalsFiltered rectified a.c. but strongly ripple-modulated
6Not usedGood signalsFiltered tone, definite trace of ripple modulation
7Not usedModerately strong signalsNear pure tone, trace of ripple modulation
8Not usedStrong signalsNear perfect tone, slight trace of modulation
9Not usedExtremely strong signalsPerfect tone, no trace of ripple or modulation of any kind


Select the signal's most consistant 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 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.

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