The RST system is used by
radio amateurs as a formalized way of giving
information on the quality of the
signal they receive (signal reports).
An RST is a number consisting of three
digits, which are transmitted
during the conversation, and written on the
QSL card in the cases where
the amateurs exchange such cards afterwards. The digits give information
on the
readability,
strength and
tone of the
signal, respectively. The tone part of the signal report is used only
for modes that can be said to have a tone, such as
CW (
morse code), RTTY, PSK, and so forth, but
not for
telephony.
Although the conventional descriptions quoted in the list below suggest
that the difference between the digits are clearly defined (sort of like the
Beaufort scale or the Mohs hardness scale, the ratings a radio
amateur gives out to a fellow radio amateur's transmission is very
subject to individual judgment.
Readability means how well you are able to understand
what the other amateur is saying (or sending). Here, 1 is the worst,
and 5 is the best.
- 1--Unreadable
- 2--Barely readable, occasional words distinguishable.
- 3--Readable with considerable difficulty.
- 4--Readable with practically no difficulty.
- 5--Perfectly readable.
Signal Strength means how much the received signal
stands out from the background noise. Many radios have so-called "S-meters", and some operators just report the number the needle stands on when it peaks. This is not a very good idea, since these instruments are not standardized from manufacturer to manufacturer, and since background noise alone may add as much as 5 to the reading. Therefore, as earlier mentioned, this is not
something you should read out on instruments, but something you should
judge with your ears.
- 1--Faint signals, barely perceptible.
- 2--Very weak signals.
- 3--Weak signals.
- 4--Fair signals.
- 5--Fairly good signals.
- 6--Good signals.
- 7--Moderately strong signals.
- 8--Strong signals.
- 9--Extremely strong signals.
Tone, on CW, means how the transmitted tone sounds.
The tone should sounds as much like a perfect sine wave as possible.
- 1--Sixty cycle a.c or less, very rough and broad.
- 2--Very rough a.c., very harsh and broad.
- 3--Rough a.c. tone, rectified but not filtered.
- 4--Rough note, some trace of filtering.
- 5--Filtered rectified a.c. but strongly ripple-modulated.
- 6--Filtered tone, definite trace of ripple modulation.
- 7--Near pure tone, trace of ripple modulation.
- 8--Near perfect tone, slight trace of modulation.
- 9--Perfect tone, no trace of ripple or modulation of any kind.
The signal report is almost always given very early in the
QSO, before
the exchange of name and
QTH, and before any
rag chewing. On CW, or
digital
modes where text is transmitted (such as
RTTY) the standard
formula for reporting the RST is, for example
UR RST RST 557
557, or
UR RST RST IS 439 439. On
phone modes
(
SSB or
FM), the most widely used phrase is "you're five and nine
here".
Note that the tone part of the signal report is not applicable in
telephony modes, and must always be omitted. Such signal reports with only two digits are sometimes called "RS". QSL cards for SSB or FM
QSOs with 3 digit RSTs are judged as invalid for use as proof in
contests and applications for diplomas.