The RT Readability Scale is a signal strength and readability outcome that is formalised by following a standardized principle.

This outcome determines the strength of the radio frequency signal and the readability (quality) of the radiotelephone (voice) signal transmitted by a station from their location. These report formats are designed for determining the radio strength of only one communications mode; i.e. – that party which is making the transmission on a selected radio frequency at the time.

 Although this Radio Telephony (RT) readability scale can be applied using numerous formats dependant on which radio discipline is being managed at the time, such as security, medical, marine, etc, it is generally formulated using 5 principles for guidance. They are listed in the following order of radio strength (with an explanation of each):

Strength One


Crackling, background noise on frequency.

Strength Two

Readable Now and Then

Only parts of a transmission can be heard with background noise that is affecting its strength.

Strength Three

Readable with Difficulty

The transmission can be heard, with background noise that may affect the transmission.

Strength Four


The transmission can be heard, with background noise that does not affect the transmission.

Strength Five

Perfectly Readable

The transmission can be clearly heard with no background noise.


Although there is a readability scale to refer to, ultimately the party on frequency that has been:

  1. Either asked to participate in a radio check, or
  2. Given feedback of a transmission that has been made by them;

Is determining the strength of that transmission based on their understanding of the radio transmission itself, plus their interpretation of the radio strength table. This could be viewed as a flaw in a system that is meant to give accurate guidance to all users of a radio frequency as there is obviously no external assistance in understanding the application of this Table. In other words, what does one use to analyse the `cut off` between a transmission strength three, and a transmission strength four for example?

There has never been a radio strength meter designed for this purpose, so ultimately this RT strength readback is the perception of the user who is determining the strength of any transmission at that time. Even a user that has been working on a radio frequency for a considerable length of time could make an error when determining the strength of any particular transmission. One could therefore deem this RT transmission test following the radio strength table to be a biased approach that is ultimately very one sided.

To date there is unfortunately no other way to determine the strength of a radio transmission than by the User asking for another party to give their outcome of a transmission made on frequency, using the radio strength table to support this decision.

In the modern age of technology, where everyone relies significantly on electronic gadgets to go about their daily tasks and activities, we find a unique situation that has ultimately been left to the fate of Human Factors to resolve? 

Do you think there is a better way to determine the strength of a radio transmission? Feel free to email me via