Signal strength and readability report
Introduction
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A signal strength and readability report is a standardized format for reporting the strength radio signal and the readability (quality) of the radiotelephone (voice) or radiotelegraph (Morse code) signal transmitted by another station of their transmission as received at one's location and by their radio station equipment. Various formats have been used over the years, and by different communications organizations.
Radiotelegraph report formats
One of the first signal report formats was the QSJ code, the initial version of the signal report format that evolved into the QSA and QRK signal reports.
The CCIR-developed SINPO code for use in radiotelegraphy, and the standard is contained in ITU-R SM.1135. This format is most notably used by the BBC for receiving signal reports on postcards mailed from listeners, even though that same standard specifies that the SINPFEMO code should be used for radiotelephony transmissions.
Amateur radio users in the U.S. and Canada have used the R-S-T system since 1934, which reports the readability on a scale of 1 to 5, signal strength on a scale of 1 to 9, and the tone of the Morse code continuous wave signal on a scale of 1 to 9. During Amateur radio contests, where the rate of new contacts is paramount, contest participants often give a perfect signal report of 599 even when the signal is lower quality, because always providing the same signal format enables them to send Morse code with less thought and thus increased speed. The R-S-T system is also used by most Amateur radio operators to describe voice transmissions, dropping the last digit because there is no continuous wave tone to report on.
Radiotelephony report formats
The signal report formats used in radiotelephone communications include:
- SINPFEMO code (rarely used)
- R-S-T system (used only by North American Amateur radio operators)
- Plain language radio checks, in use since World War II
In analog radio systems, as receiving stations move away from an analog radio transmitting site, the signal strength decreases gradually, causing the relative noise level to increase. The signal becomes increasingly difficult to understand until it can no longer be heard as anything other than static.[1]: 38
The move to plain-language radio communications means the number-based formats are now considered obsolete, to be replaced by plain language radio checks, which avoid the ambiguity of which number stands for which type of report and whether a 1 is considered good or bad.
These reporting systems are usable with, but perhaps not completely appropriate for rating digital signal quality. This is because digital signals have fairly consistent quality as the receiver moves away from the transmitter until reaching a threshold distance. At this threshold point, sometimes called the "digital cliff," the signal quality takes a severe drop and is lost.[1]: 38 This difference in reception reduces attempts to ascertain subjective signal quality to simply asking, "Can you hear me now?" or similar. (The only possible response is "yes"; otherwise, there is just dead air.) This sudden signal drop was also one of the primary arguments of analog proponents against moving to digital systems. However, the "five bars" displayed on many cell phones does directly correlate to the signal strength rating.
Slang report formats
A report format commonly referred to as five by five is often used in media. The report format ostensibly consists of two digits, each ranging from 1 to 5, resulting in 25 possible combinations, with five by five being the best signal possible out of 25 combinations. However, as no reliable source has been found documenting this format, it may simply be Cold War-era slang, inappropriately mapping the radiotelegraph signal report numbers to radiotelephony signals.
Some radio users have inappropriately started using the Circuit Merit telephone line quality measurement. This format is unsuitable for radiotelegraph or radiotelephony use because it focuses on voice-to-noise ratios, for judging whether a particular telephone line is suitable for commercial (paying customer) use, and does not include separate reports for signal strength and voice quality.
See also
- Procedure word
- Mean opinion score
- Perceptual Evaluation of Speech Quality
- Perceptual Objective Listening Quality Assessment
References
- ^ a b Imel, Kathy J.; Hart, James W. (January 2003). "Understanding Wireless Communications in Public Safety" (PDF). FCC.gov. The National Law Enforcement and Corrections Technology Center–Rocky Mountain. Retrieved September 19, 2015.
External links
- Ham Radio RST Signal Reporting System for CW Operation, by Charlie Bautsch, W5AM
- itu.int: SM.1135 - Sinpo and sinpfemo codes - ITU