Everyone wants to know how their signal sounds on the air. Often, the best way to find out is to get a signal report from other ham radio operators. The two main report options are the RST system and the S-meter. Both are widely used but serve slightly different purposes and may be used in different contexts. Here’s a comparison of both options to help you decide which one to use in various situations.
RST
The RST system is one of the most commonly used methods for reporting signal quality in amateur radio communications. It stands for Readability, Signal Strength, and Tone. An RST report provides a three-part evaluation of the signal that is being received. This system replaced a more complicated one that had been in use since the early days of radio.
A perfect signal on phone is RS 59 or just 59. You’ll typically hear something like this on the HF bands: “Your signal report is five-nine in central Ohio.” Radios do not have an R-meter, so the R part of a signal report is purely subjective. If you are a good copy, you will usually get a five for readability—perfectly readable. A four indicates you’re readable with practically no difficulty, and three means readable with considerable difficulty. Most signal reports range from R3 to R5, with lower numbers indicating progressively weaker signals.
The T, or tone factor, refers to the sound qualities of the received CW signal. Older vacuum tube rigs, for various reasons, often produced hum and warbly tones. With today’s more stable rigs, the T is always a 9. In digital modes like FT8, the tone part is typically ignored, focusing on readability and strength. The best signal report for CW operation is RST 599.
9 Signal Strength Levels–a Lot of Somewhat Subjective Choices
So, how do you differentiate between a 5 and a 6? You do your best with the S, opting to err on the generous side. The perceived signal strength is also affected by the settings of the receiving station’s RF and AF gain controls and maybe the battery level in the op’s hearing aids. QRM and QRN are also factors you need to consider.
RST Evaluation Chart
| Readability | Signal Strength | Tone (Morse Code) | |
|---|---|---|---|
| 1 | Unreadable | Faint | Harsh tone with hum |
| 2 | Barely readable | Very weak | Harsh tone with modulation |
| 3 | Readable with difficulty | Weak | Rough tone with hum |
| 4 | Almost perfectly readable | Fair | Rough tone with modulation |
| 5 | Perfectly readable | Fairly good | Wavering tone, strong hum |
| 6 | — | Good | Wavering tone, strong modulation |
| 7 | — | Moderately strong | Good tone, slight hum |
| 8 | — | Strong | Good tone, slight modulation |
| 9 | — | Very strong | Perfect tone, no hum or modulation |
S-Meter Report
The S-meter is a simple yet highly effective tool used in most modern ham radios. It provides a quantitative measurement of signal strength on a logarithmic scale, usually from S1 to S9, where S1 is the weakest signal and S9 is a standard reference level for strong signals. The meter updates in real–time, providing operators with a quick visual readout of how strong a signal is. Many radios feature readings higher than S9, such as S9+10 or S9+20, indicating extremely strong signals.
S-meters are a more quantitative system than the RST report, since they measure signal strength without considering readability or tone. It’s commonly used by operators who want a more straightforward, visual representation of signal strength. But it’s important to realize some variations in S-meter calibration—signal reports can vary from radio to radio. The S9 “standard” is commonly defined as 50 µV at the receiver input, with each S unit representing a 6 dB change in signal strength.
A 56 or 57 report indicates that the signal is very readable, but the signal strength is not as strong as that of a 59 signal. Then there are the really strong ones. You’ll hear amateurs say, “You’re 59 plus 20 dB.” Or they may report, “You’re 20 dB over 9.”
One of the main drawbacks is that the S-meter only reports strength, not the overall quality of the signal or readability. A signal might show as S9 on the meter but still be hard to understand due to static, fading, or other interference. For example, strong signals can sometimes have distortion, making them harder to hear despite high readings on the S-meter.
Which One Should You Use?
- For a quick, straightforward evaluation of signal strength, especially in voice or digital modes, the S-meter is often sufficient.
- For a more detailed, qualitative report, particularly if you’re working with Morse code or in situations with varying signal conditions (like DXing), the RST system provides a more comprehensive picture.
- For complete communication, you can combine both, using the S-meter for a real-time signal strength reading and the RST system to describe the signal’s overall quality.
- The RST system is the standard in many ham radio contests and formal communications. It is universally understood, making it ideal for reporting in these situations.
- Some nets, such as the 3905 Century Club, use RST reports to confirm successful contacts.
Both the RST system and the S-meter serve valuable purposes, but the choice between them depends on your communication context. If you need to provide a detailed report of both signal quality and strength, the RST system is the best option. The S-meter works well if you’re looking for a simple, real-time signal strength reading. Using both can offer the most complete understanding of signal conditions for most ham radio operations.
Final Thoughts
RST or S-meter readings are good, but sometimes the operator on the other end is looking for a more critical evaluation of their signal quality. Suppose they say something about checking out this new microphone or working on solving an audio problem. That may be the clue to spend a little extra time carefully listening to the signal and providing more comments on how it sounds. Most of us don’t hear our own signal on the air, so getting quality feedback from other radio amateurs is invaluable.
Try to give a realistic signal report. Most operators want the truth, and they want to know how band conditions are between your station and their location. However, “rubber stamp” signal reports are often given as 599 in contesting and contacting DX stations. No matter how weak or strong your or their signal is, you get or give a 59! Basically, they are trying to work as many stations as fast as possible and don’t want to be bothered with accurate signal reports, so everyone gets a perfect report.
