Caibrate S-Meters...how??? What is right

  • I will calibrate my S-Meter on SDR-Radio...


    What is right on QO-100:

    -73dBm = S9 (like this goes up to 30MHz)

    -93dBm = S9 (like this goes from 30MHz)


    How is the noise level defined?

    On the Web-SDR (eshail.batc.org.uk) the noise level goes to S6.


    The most OM`s are S9+, I think that is not right... or???


    I know the signal to noise is right.

    What are yoo doing?


    73 de Wolfgang

  • Take the NBTP floor as S0 (ca -127dB) and then the CW beacon has abt S5+3dB.


    Strong stations have a signal about S6.


    Everything above is unwanted and to much uplink power.


    The strongest HAM station i saw till now had S7+3dB. (SSB)


    BTW, Forget the S-Meters on the WEB-SDRs they are all wrong.


    VY73 DB8TF

  • Hello all,


    I use the old ARRL-way of "best guessing" by ear:


    1 - Faint signals, barely perceptible

    2 - Very weak signals

    3 - Weak signals

    4 - Fair signals

    5 - Fairly good signals

    6 - Good signals

    7 - Moderately strong signals

    8 - Strong signals

    9 - Extremely strong signals


    Any signal around the beacon signal for me is in the S9 range (as suggested by Peter). People who just make it a few dB above the noise get an "S1 or S2" from me.



    Best 73


    Holger 'Geri', DK8KW

  • Looking at the BATC WebSDR as well as the one from IS0GRB, the CW beacon is about 15-16dB over the noise. An S-point is 6 dB so the "best" we can do (before getting a QSL card from LEILA) would be 2.5 S-point above the noise.


    The question then, is where you lie "zero". With all the mixing and amplification making an absolute measurement is hard. And I see that the 50-60dB gain of the LNB drives many receivers hard: if the noise floor is S8, are the signals well received and nice to listen to even if they are 59+10dB?


    I tend to attenuate so that the noise is S1-S2, this makes the receiver a lot better behaving to but it would mean that the best report I can give is S5 or so.


    And that doesn't even bring the poor calibration of an S-meter into the equation, I'm inclined not to use "five-nine" at all.


    Perhaps using the dB's of one of the WebSDR's is more accurate than an S-meter report?


    Geert Jan

  • Personally, for me this is a non issue and endlessly discussed in the past on other bands, with and/or without the use of transverters.


    There is almost nobody having a real logarithmic S-meter (the S-meter is very often derived from the AGC voltage).


    I use the ARRL-method with odd numbers. In case of doubt, the QSO-partner earns an extra point ; -)

  • OK I will check... why -127 is over 30MHz then -147????