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Never get too pedantic about S Meter readings. These must be the most talked about topic on the air. True to say the figures "over nine" lend importance to a report and the graphic use of red in some designs make the listener feel something really special - even somehow dangerous, possibly harmful to the set - is going on, but they are for the most part only a guide. Have fun with them by all means but please do not hold them up as gospel.
Only in a few classic designs has the law on which the S Meter scale is based been fully interpreted. Even then the antenna has to be an EXACT match to the input impedance of the set with no compromises. Radio hams exchanging signal reports should realise that to be of any value, the two operating stations must be identical from the ground up. Quite literally, as soil conductivity around an antenna is a vital part of its characteristics. Having said all that, what kind of voltages exist at the antenna socket?
| S Meter reading | Antenna PD | SINPO | Perceived Strength |
| S9+60dB | 50 millivolts | 5 | Acutely strong |
| S9+50dB | 16 millivolts | 5 | Acutely strong |
| S9+40dB | 5 millivolts | 5 | Extremely strong |
| S9+30dB | 1.6 millivolts | 4 | Extremely strong |
| S9+20dB | 500 microvolts | 4 | Extremely strong |
| S9+10dB | 160 microvolts | 3 | Extremely strong |
| S9 | 50 microvolts | 3 | Very strong |
| S8 | 25 microvolts | 3 | Strong signals |
| S7 | 12 microvolts | 2 | Moderately strong |
| S6 | 6 microvolts | 2 | Good signals |
| S5 | 3 microvolts | 2 | Fairly good signals |
| S4 | 1.5 microvolts | 2 | Fair signals |
| S3 | 0.8 microvolts | 1 | Weak signals, DX |
| S2 | 0.4 microvolts | 1 | Very weak signals, rare DX! |
| S1 | 0.2 microvolts | Barely usable signals |
Where the signal is acutely strong, report the level but listen on the attenuator. With signals this strong, there is no need for the real performance of a communications receiver so avoid overload distortion with a prod at the ATTN button.
The SINPO levels are my invention. They are "marks out of five" for Signal strength, Interference, Noise level, Propagation path and an Overall rating.
Your scribe only reports "fair", "good" or "excellent" since the modern radio memory system is the station log and whatever is held in there has to have some entertainment value.
However the hobby seems to demand lots of numbers, so here are a few more in a marks-out-of-five rating for readability;
| R | Readability |
| R5 | Perfectly readable |
| R4 | Readable with little difficulty |
| R3 | Readable with considerable difficulty |
| R2 | Barely readable, occasional words audible |
| R1 | Unreadable |
So, a "five and nine" report is an excellent signal, something like a "one and two" isn't worth staying up for. We do enjoy hearing reports of ones and twos on 80m, the chap going on to say, "but I don't care what the meter says - I'll give you a five and eight because I heard every word!"