SINPO, acronym for signal, interference, noise, propagation, and overall, is a Signal Reporting Codes used to describe the quality of radio transmissions, especially in reception reports written by shortwave listeners. Each letter of the code stands for a specific factor of the signal, and each item is graded on a 1 to 5 scale (where 1 stands for nearly undetectable/severe/unusable and 5 for excellent/nil/extremely strong).
The code originated with the CCIR (a predecessor to the ITU-R) in 1951, and was widely used by BBC shortwave listeners to submit signal reports, with many going so far as to mail audio recordings to the BBC's offices. It has been expanded in some places to a SINPFEMO code which includes rating the station's modulation and other audio qualities, but the expanded code is rarely used in practice.
Both SINPO and SINPFEMO are the official signal reporting codes for international civil aviation.
The use of the SINPO code can be subjective and may vary from person to person. Not all shortwave listeners are conversant with the SINPO code and prefer using plain language instead.
- S (Signal strength)
- The relative strength of the transmission.
- I (Interference)
- Interference from other stations on the same or adjacent frequencies (man-made noise).
- N (Noise)
- The amount of atmospheric noise.
- P (Propagation)
- Whether the signal is steady or fades from time to time.
- O (Overall merit)
- An overall score for the listening experience under these conditions.
Each category is rated from 1 to 5 with 1 being 'unusable' or 'severe' and 5 being 'perfect' or 'nil'. MANY raters misunderstand the code and will rate everything either 55555 or 11111 when in reality both extremes are unusual in the extreme. '55555' essentially means 'perfect reception akin to a local station' while that is occasionally possible, when talking about long-distance short-wave reception, it is almost never the case.
Another common mistake in rating is presenting an 'O' higher than any previously rated element. By definition, a station cannot present 'perfect' reception if there is any Noise or Interference or Fading present. In other words, it is NOT 'perfect local quality' reception if any of those things are present.
|Signal||Interference||Noise||Propagation conditions||Overall merit|
|1-Barely Audible||1-Extremely strong||1-Extremely strong||1-Very poor propagation||1-Useless|
Examples of SINPO code applied
In responding to a shortwave reception, the SINPO indicates to the transmitting station the overall quality of the reception.
The SINPO code in normal use consists of the 5 rating numbers listed without the letters, as in the examples below:
54554 - This indicates a relatively clear reception, with only slight interference; however, nothing that would significantly degrade the listening experience.
33433 - This indicates a signal which is moderately strong, but has more interference, and therefore deterioration of the received signal.
Generally, a SINPO with a code number starting with a 2 or lower would not be worth reporting, unless there is no noise, interference or loss of propagation, since it would be likely the signal would be unintelligible.
Although the original SINPO code established technical specifications for each number (i.e., a number 3 in the P column meant a fixed number of fades per minute), these are rarely adhered to by reporters. The 'S' meter displays the relative strength of the received RF signal in decibels; however, this should not be used as the sole indication of signal strength, as no two S meters are calibrated exactly alike, and many lower-priced receivers omit the S meter altogether. References to a "SINFO" code may also be found in some literature. In this case, the 'F' stands for Fading, instead of 'P' for Propagation, but the two codes are interchangeable. It was presumed that the average listener would be more familiar with the meaning of "fading" than "propagation". A simple way to insure the rating applied is useful is to rate the "O" column first based on the intelligibility of the station. If you can understand everything easily, the station will rate a 4 or higher. If you have to work hard, but can understand everything '3' is the appropriate rating. If you cannot understand everything although you put great effort into it, a '2' is appropriate, and if you cannot understand the programming at all '1' is the appropriate rating.
Some listeners may not know how to distinguish between the 'I' which indicates interference from adjacent stations, and the 'N' which describes natural atmospheric or man-made noise; also for some listeners, the rating for 'Propagation' may not be completely understood. As a result of this confusion, many stations suggest the SIO code -- a simpler code which makes the limitations noted above not relevant. Despite this, some books and periodicals maintain the SINPO code is the best for DX reporters.
- "BBC Engineering Division Monnograph, Number 43: September 1962" (PDF).
- "Procedures for Air Navigation Services: ICAO Abbreviations and Codes" (PDF). Retrieved 27 April 2015.
- "Reception Reports: Reporting Code - Writing Useful Reception Reports". Retrieved 27 April 2015.