There have been a few recent interesting discussions relating to S/N
observations and calculations based upon S-meter readings. Let it be known
that S-units are entirely arbitrary meter markings, serving some higher good
mandated by the particular manufacturer of the radio in question.
The issue is hereby put to rest by means of a simply performed accurate
calibration of the S meters on 2 FT1000MP's. I used a highly accurate
calibrated signal source (HP 8920E) and checked the calibration on all bands;
there was essentially no difference from band to band except for a few db
overall offset on 160M.
As suspected the "value" of an S-unit varies from about 2db at s1+ to 10db at
Hence, the only way to accurately use S-meter readings is by converting them
to absolute dbm or dbv by means of this or a similar calibration chart.
I will send a copy of the calibration data to anyone upon email request.
Eric von Valtier K8LV