[Elecraft] MDS practical measuring?

[Brian Alsop]

It was time to drag out the test gear and give my older K3 a going over.

One thing of interest was Minimum Detectible Signal.

There is a WIKI definition for it but the equation doesn't help me a bit.

I just thought I'd attach a calibrated signal generator and keep 
reducing the level (for a 500 Hz bandwidth) until I couldn't hear it.
That doesn't seems subjective since the signal generator is a constant 
tone and not information to decode.

Then I tried looking at Spectrogram and defining a minimum S/N ratio 
which would define MDS.  The MDS values derived this way were much lower 
for a 6 dB S/N ratio.  In fact, I couldn't hear the signal at this S/N 
ratio!  The integration time constant used for averaging clearly was 
helping with detection.  So what time constant would be appropriate for 
normal CW?

How indeed is MDS measured quantitively?

73 de Brian/K3KO


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