How are your 'ears'-- your ability to copy very weak CW signals? Here's a way to "measure" your ears. You'll need your panadapter set to a narrow span such as 2 kHz. Turn on averaging so that the noise flattens out to allow you to estimate the true level of the noise. Use a full-screen vertical scale of just a few dB to make it easy to measure small signals just above the noise.
Whatever your noise floor is, when a signal creates a 3 dB "bump" above the noise floor, that means the signal and noise are equal (because if you add two equal powers you get twice the power, which is a 3 dB bump). We call this condition a "signal-to-noise ratio of 0 dB". Now tune around the band to find very weak signals and see how much of a bump they make. Here are some rough rules of thumb, rounded off for simplicity: Height of bump above noise S/N ratio 6 dB 5 dB 5 3 dB 4 dB 2 dB 3.5 dB 1 dB 3 dB 0 dB 2.5 dB -1 dB 2 dB -2 dB 1.8 dB -3 dB I listed some negative S/N ratios because I've heard of folks who can copy signals below the noise floor! That's crazy! In any case, this is a very approximate measurement, but it's fun having some idea how well you can actually copy CW at phenomenally low levels. Al W6LX ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
