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 as a suffix. 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. The character "N" (dah-dit) is often used as an abbreviation for the numeral 9 (dadadadah-dit) to shorten the process.
In this case, the RST signal report may be sent as "RST is 5NN".
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.