From Wikipedia: https://en.wikipedia.org/wiki/S_meter
"IARU Region 1 Technical Recommendation R.1 defines S9 for the
HF bands to be a receiver input power of -73 dBm. This is a level
of 50 microvolts at the receiver's antenna input assuming the
input impedance of the receiver is 50 ohms.
For VHF bands the recommendation defines S9 to be a receiver
input power of -93 dBm. This is the equivalent of 5 microvolts
in 50 ohms."
Alan N1AL
On 11/18/2015 03:46 PM, Bob McGraw - K4TAX wrote:
The original S meter development for HF radios was done by Art Collins.
At that time the number used was 100 uV for S-9 to coincide with the RST
system. Later the value was revised to 50 uV for S-9. Values above S -
9 are stated usually in dB although I've seen some in microvolts. If
one ventures into the VHF spectrum then the value changes. {I forget to
what value}
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