"Roy Lewallen" wrote in message
...
Just don't make the common mistake of thinking that the units on your
receiver's S meter are 6 dB. That can lead to some extremely mistaken
conclusions.

Hams keep insisting that an "S-unit" is 6 dB, while the marks on typical
S-meters almost never are, and sometimes are much different ( 2 dB for
example).

Roy Lewallen, W7EL

The following are my findings on an IC751, which I had previously posted on
another NG:
"As an example; the Icom IC-751 S meter calibration procedure requires that
the S meter adjustment pot be set to S9 +40dB, with 5 mV at the antenna
input. The S meter should then be verified to show: S8 - S9 with 50 uV
input, and S2 - S3 with 5 uV input. Note that this approximates to 3.33dB
per S unit. The amateur standard has traditionally been 6 dB per S unit.

I have calibrated my IC-751 as per the manual instructions. 50 uV reads S9
+ 15 dB, and 5uV reads S5. Increasing the generator above 5uV requires 11
dB to reach S9, or 2.75 dB per S unit."

I have seen it claimed that linear amplifiers often provide more than the
theoretical gain, and that the cause is some indefinable ionospheric
nonlinearity rather than meaningless S meters!

Regards,

Frank