The QSA code and QRK code are interrelated and complementary signal reporting codes for use in wireless telegraphy (Morse code). An enhanced format, SINPO code, was published in the ITU Radio Regulations, Geneva, 1959, [1] but is longer and unwieldy for use in the fast pace of Morse code communications.
The current definition of the QSA and QRK codes are officially defined in ITU Radio Regulations 1990, Appendix 13: Miscellaneous Abbreviations and Signals to Be Used in Radiotelegraphy Communications Except in the Maritime Mobile Service, and are also described identically in ACP131(F),: [2]
Signal | Question | Answer, Advice, or Order |
---|---|---|
QSA | What is the strength of my signals (or those of...)? | The strength of your signals (or those of...) is...
|
QRK | What is the intelligibility of my signals (or those of...)? | The intelligibility of your signals (or those of...) is...
|
The QSK code is one of the earliest signal reporting formats and is a part of the Q code used for commercial radiotelegraph communication, appearing as one of the twelve Q Codes listed in the 1912 International Radiotelegraph Convention Regulations, and was later adopted by other radio services, especially amateur radio. The QSA code was mandated by the Madrid Convention (Appendix 10, General Regulations) sometime prior to 1936, and specified the following reporting format, as found in the 1936 edition of the ARRL's The Radio Amateur's Handbook [3] and Radiotelegraph & Radiotelephone Codes, Prowords, and Abbreviations. [1]
Request from first station | Response from receiving station | Meaning |
---|---|---|
QRK (replaced earlier QJS) | QSA1 | Hardly perceptible, unreadable |
QSA2 | Weak, readable now and then | |
QSA3 | Fairly good, readable but with difficulty | |
QSA4 | Good, readable | |
QSA5 | Very good, perfectly readable |
The book goes on to note that "Some of the definitions, however, appear to confuse audibility or signal strength with readability, which may be impaired even when signals are strong, by atmospherics, interference, a noisy receiver, etc.", and that because of this Amateurs supplemented the QSA system reports with a readability scale, called the R-System, which used a scale of 1 to 9. The book describes the QSA- and R-systems immediately after describing the R-S-T system, and notes that the R-S-T report format, because it is three digits long, cannot be confused with either of the earlier systems. The book does not clarify the method for requesting an R-S-T report instead of a QSA report. [3]
The U.S. Navy's Communications Instructions of 1929 prescribed a different set of codes for the response: [4] However, for joint Army-Navy operations, the K signal was replaced with the S signal, with exactly the same definitions. [5]
Response from receiving station | Meaning |
---|---|
R1 | Unreadable |
R2 | Poor but readable—send each character twice. |
R3 | Fair—readable at slow speed, send code twice. |
R4 | Good—readable at moderate speed. |
R5 | Easily readable. |
Response from receiving station | Meaning |
---|---|
K1 | Very weak—hardly audible. |
K2 | Moderately weak. |
K3 | Medium strength. |
K4 | Moderately strong. |
K5 | Strong. |
An expanded QRK code was first defined to go along with the earlier QSA code in the ITU Radio Regulations Cairo, 1938. [1]
Request from first station | Response from receiving station | Meaning |
---|---|---|
QSA (replaced earlier QJS) | QSA1 | Hardly perceptible, unreadable |
QSA2 | Weak, readable now and then | |
QSA3 | Fairly good, readable but with difficulty | |
QSA4 | Good, readable | |
QSA5 | Very good, perfectly readable |
Request from first station | Response from receiving station | Meaning |
---|---|---|
QRK | R1 | Unreadable |
R2 | Occasional words distinguishable | |
R3 | Readable with difficulty | |
R4 | Readable with almost no difficulty | |
R5 | Perfectly readable |
The 1945 U.S. Army Radio Operator's Manual, FM 24-6 defines the radiotelegraph signal report format as follows: [6]
Report | Readability | Signal Strength |
---|---|---|
1 | Unreadable | Scarcely perceptible |
2 | Readable now and then | Weak |
3 | Readable but with difficulty | Fairly good |
4 | Readable | Good |
5 | Perfectly readable | Very good |
FM 24-6 further states, "Readability and signal strength reports indicate the desired method of transmission and should be used in that sense. Readability and signal strength reports are not exchanged unless "3" or less, lack of any report being assumed to indicate satisfactory communications."
The report example given below uses military call signs and the obsolete Q Code of QJS for readability instead of the current QRK:
Station | Transmission |
---|---|
MB6 | 3MY V MB6 QJS 3 K |
3MY | MB6 V 3MY INT QJS K |
MB6 | 3MY V MB6 QJS 4 AR |
MB6 | S7P V MB6 INT QJS INT QSA K |
S7P | MB6 V S7P QJS 3 QSA 3 AR |
The 1943–1945 Combined Communications Board Publications, including CCBP 3-2: Combined Radiotelephone (R/T) Procedure, [7] describe a slightly newer radiotelephony version of the radiotelegraph procedure described in the U.S. Army Radio Operator's Manual, FM 24-6:
(a) A station is understood to have good readability unless otherwise notified. Strength of signals and readability will not be exchanged unless one station cannot clearly hear another station.
(b) The response to "How do you hear me?" will be a short concise report of actual reception such as "Weak but readable," "Strong but distorted," "Loud and clear," "Strength Four," etc.
At least in CCBP 3–2, no additional detail is given about what the range of the numeric scale is, or the complete list of strength and readability code words are.
Morse code is a method used in telecommunication to encode text characters as standardized sequences of two different signal durations, called dots and dashes, or dits and dahs. Morse code is named after Samuel Morse, one of the inventors of the telegraph.
The (International) Radiotelephony Spelling Alphabet, commonly known as the NATO phonetic alphabet, is the most widely used set of clear code words for communicating the letters of the Roman alphabet. Technically a radiotelephonic spelling alphabet, it goes by various names, including NATO spelling alphabet, ICAO phonetic alphabet and ICAO spelling alphabet. The ITU phonetic alphabet and figure code is a rarely used variant that differs in the code words for digits.
The Q-code is a standardised collection of three-letter codes that each start with the letter "Q". It is an operating signal initially developed for commercial radiotelegraph communication and later adopted by other radio services, especially amateur radio. To distinguish the use of a Q-code transmitted as a question from the same Q-code transmitted as a statement, operators either prefixed it with the military network question marker "INT" or suffixed it with the standard Morse question mark UD.
Mayday is an emergency procedure word used internationally as a distress signal in voice-procedure radio communications.
SOS is a Morse code distress signal, used internationally, that was originally established for maritime use. In formal notation SOS is written with an overscore line, to indicate that the Morse code equivalents for the individual letters of "SOS" are transmitted as an unbroken sequence of three dots / three dashes / three dots, with no spaces between the letters. In International Morse Code three dots form the letter "S" and three dashes make the letter "O", so "S O S" became a common way to remember the order of the dots and dashes.
The Allied military phonetic spelling alphabets prescribed the words that are used to represent each letter of the alphabet, when spelling other words out loud, letter-by-letter, and how the spelling words should be pronounced for use by the Allies of World War II. They are not a "phonetic alphabet" in the sense in which that term is used in phonetics, i.e. they are not a system for transcribing speech sounds.
The R-S-T system is used by amateur radio operators, shortwave listeners, and other radio hobbyists to exchange information about the quality of a radio signal being received. The code is a three digit number, with one digit each for conveying an assessment of the signal's readability, strength, and tone. The code was developed in 1934 by Amateur radio operator Arthur W. Braaten, W2BSR, and was similar to that codified in the ITU Radio Regulations, Cairo, 1938.
A signal strength and readability report is a standardized format for reporting the strength of the radio signal and the readability (quality) of the radiotelephone (voice) or radiotelegraph signal transmitted by another station as received at the reporting station's location and by their radio station equipment. These report formats are usually designed for only one communications mode or the other, although a few are used for both telegraph and voice communications. All but one of these signal report formats involve the transmission of numbers.
Radiotelephony procedure includes various techniques used to clarify, simplify and standardize spoken communications over two-way radios, in use by the armed forces, in civil aviation, police and fire dispatching systems, citizens' band radio (CB), and amateur radio.
SINPO, an acronym for Signal, Interference, Noise, Propagation, and Overall, is a Signal Reporting Code used to describe the quality of broadcast and radiotelegraph transmissions. SINPFEMO, an acronym for Signal, Interference, Noise, Propagation, frequency of Fading, dEpth, Modulation, and Overall is used to describe the quality of radiotelephony transmissions. SINPFEMO code consists of the SINPO code plus the addition of three letters to describe additional features of radiotelephony transmissions. These codes are defined by Recommendation ITU-R Sm.1135, SINPO and SINPFEMO codes.
Procedural signs or prosigns are shorthand signals used in Morse code radio telegraphy procedure, for the purpose of simplifying and standardizing radio communication protocol. They are separate from Morse code abbreviations, which consist mainly of brevity codes that convey messages to other parties with greater speed and accuracy.
Morse code abbreviations are used to speed up Morse communications by foreshortening textual words and phrases. Morse abbreviations are short forms, representing normal textual words and phrases formed from some (fewer) characters taken from the word or phrase being abbreviated. Many are typical English abbreviations, or short acronyms for often-used phrases.
A spelling alphabet is a set of words used to represent the letters of an alphabet in oral communication, especially over a two-way radio or telephone. The words chosen to represent the letters sound sufficiently different from each other to clearly differentiate them. This avoids any confusion that could easily otherwise result from the names of letters that sound similar, except for some small difference easily missed or easily degraded by the imperfect sound quality of the apparatus. For example, in the Latin alphabet, the letters B, P, and D sound similar and could easily be confused, but the words "bravo", "papa" and "delta" sound completely different, making confusion unlikely.
A radiogram is a formal written message transmitted by radio. Also known as a radio telegram or radio telegraphic message, radiograms use a standardized message format, form and radiotelephone and/or radiotelegraph transmission procedures. These procedures typically provide a means of transmitting the content of the messages without including the names of the various headers and message sections, so as to minimize the time needed to transmit messages over limited and/or congested radio channels. Various formats have been used historically by maritime radio services, military organizations, and Amateur Radio organizations.
Procedure words are words or phrases limited to radio telephone procedure used to facilitate communication by conveying information in a condensed standard verbal format. Prowords are voice versions of the much older procedural signs for Morse code which were first developed in the 1860s for Morse telegraphy, and their meaning is identical.
The Circuit Merit system is a measurement process designed to assess the voice-to-noise ratio in wired and wireless telephone circuits, especially the AMPS system, and although its reporting scale is sometimes used as input for calculating mean opinion score, the rating system is officially defined relative to given ranges of voice-to-noise ratios.
A plain-language radio check is the means of requesting and giving a signal strength and readability report for radiotelephony (voice) communications, and is the direct equivalent to the QSA and QRK code used to give the same report in radiotelegraph communications. SINPEMFO code is the voice signal reporting format developed by the ITU in 1959, but sees little use outside of shortwave listeners.
16-line message format, or Basic Message Format, is the standard military radiogram format for the manner in which a paper message form is transcribed through voice, Morse code, or TTY transmission formats. The overall structure of the message has three parts: HEADING, TEXT, and ENDING. This heading is further divided into procedure, preamble, address, and prefix. Each format line contains pre-defined content. An actual message may have fewer than 16 actual lines, or far more than 16, because some lines are skipped in some delivery methods, and a long message may have a TEXT portion that is longer than 16 lines by itself.
Allied Communication Procedures is the set of manuals and supplements published by the Combined Communications Electronics Board that prescribe the methods and standards to be used while conducting visual, audible, radiotelegraph, and radiotelephone communications within NATO member nations. These procedures relate to procedure words, radiotelephony procedure, Allied Military phonetic spelling alphabets, plain language radio checks, the 16-line message format (radiogram), and others.
Allied Communications Publications are documents developed by the Combined Communications-Electronics Board and NATO, which define the procedures for communicating in computer messaging, radiotelephony, radiotelegraph, radioteletype (RATT), air-to-ground signalling, and other forms of communications used by the armed forces of the five CCEB member countries and/or NATO.