Recently I bought a cheap Surecom radio for 2m and 70cm. Unfortunately, this radio has no proper S-Meter, only a number that indicates the signal strength. In this article I tried to create a translation table to S-Levels.
Measured with no modulation. Surecom directly connected to signal generator with 40cm RG223 cable. Frequency was the band midpoint (145MHz on 2m, 435MHz on 70cm)
|S-Level||dBm||Surecom value 2m||Surecom value 70cm||Note|
|S4||-123||<48||<32||Squelch @ Level 1 opens on 70cm|
|S3||-129||<48||<32||Squelch @ Level 1 opens on 2m|
|S2||-135||<32||<32||AF: 1kHz, Dev.: 3kHz; Modulation starts to be audible @ -130dBm|
|S1||-141||<32||<32||There is something in the noise 😉|
The Shurecom values seem to be in dB since the step size in dBm is equal to the value change on the radios display. I would say the receiver is not bad but the receiving level indicator is quite useless when calibrating to IARU standards. Nevertheless, many "good" radios also do not comply with the IARU standard, so I tried to find my own S-meter definition for the Surecom.
I defined the value "100" as S9 on 2m and 70cm. Then I searched for the input level at wich the Surecom shows "100". In the next step the input levels for all other S-Levels were calculated and the corresponding Surecom values were measured. All measurements were taken with 1kHz frequency modulation @ 3kHz deviation.
This is not a great standard because most stations would be around S2-3 at my QTH. I have to compare the Shurecom to another radio in the future.