SINPO is a method of evaluating a radio signal by rating Strength, Interference, Noise, Propagation, and Overall signal quality by giving each of these categories a value of 1 to 5, with higher numbers meaning better signal quality. The five letters stand for the following qualities, graded on a scale of 1 to 5, where '1' means the quality was very bad and '5' very good.
- S - Signal strength
- I - Interference with other stations or broadcasters
- N - Noise ratio in the received signal
- P - Propagation (ups and downs of the reception)
- O - Overall merit
A perfect signal would rate SINPO 55555. Although this is a subjective measure, with practise the grading becomes more consistent, and a particular broadcast may be assessed by several listeners from the same area, in which case the broadcaster could assess correspondence between reports.
After listening to a broadcast, the listener writes a report with SINPO values, typically including his geographical location (called QTH in amateur radio teminology) in longitude and latitude, a brief description of the programme listened to, their opinion about it, suggestions if any, and so on.
The listener can send the report to the broadcaster either by post or email, and request verification (QSL) from them.
Variants of the SINPO report are:
- The SIO report which omits the Noise and Propagation,
- Grading on a scale of 1 to 3 (instead of 1 to 5) and
- The SINFO report where the F stands for fading.