The “readability / signal strength / tone”, or RST system is a common way for ham radio operators to express another’s signal strength as well as how well you can understand their broadcast. A signal report of “five by nine” or “fifty-nine” indicates a great readability and signal strength (as measured on an S-meter, which is usually built into your transceiver). The first digit represents readability, the second digit represents signal strength. That values and what they mean can be referenced below. On digital modes, such as CW, RTTY, and PSK there is a third digit that represents tone. In the case of digital, an example of a perfect report would be “599”.
Readability
- Unreadable
- Barely readable, occasional words distinguishable.
- Readable with considerable difficulty.
- Readable with practically no difficulty.
- Perfectly readable.
Signal Strength
- Faint signals, barely perceptible.
- Very weak signals.
- Weak signals.
- Fair signals.
- Fairly good signals.
- Good signals.
- Moderately strong signals.
- Strong signals.
- Extremely strong signals.
Tone
- Sixty cycle a.c or less, very rough and broad.
- Very rough a.c., very harsh and broad.
- Rough a.c. tone, rectified but not filtered.
- Rough note, some trace of filtering.
- Filtered rectified a.c. but strongly ripple-modulated.
- Filtered tone, definite trace of ripple modulation.
- Near pure tone, trace of ripple modulation.
- Near perfect tone, slight trace of modulation.
- Perfect tone, no trace of ripple or modulation of any kind.
If the signal has the characteristic steadiness of crystal control, add the letter X to the RST report. If there is a chirp, the letter C may be added to so indicate. Similarly for a click, add K. The above reporting system is used on both cw and voice, leaving out the “tone” report on voice. Turn card over for examples.