Sinpo

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.

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.

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.

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