[Elecraft] Three Recordings

[Kok Chen]

The spectra can be seen at

http://homepage.mac.com/chen/temp/audio1.png

http://homepage.mac.com/chen/temp/audio2.png

http://homepage.mac.com/chen/temp/audio2.png

(Estimated using cocoaModem's spectrum display with 1.5 second exponential averaging of each FFT bin.  Please ignore the red markers, those are the default RTTY tone pairs :-))

Each horizontal dotted green line is a 20 dB step.  Labels in the horizontal axes are in Hz.

#1 is a typical flat passband and "brick wall" transition band, with very low noise floor in the stop band.  Probably from DSP filtering of some kind.  But since sharp skirts like this does not occur in nature, it might actually be more fatiguing to the human ear/brain in the long term.

#2 has a couple of spurs and minor bumps, but not as weird as #3.

#3 is the weirdest looking one.  Even though the passband is narrower than #1 and #2, the noise immediately outside the passband is quite high and slowly tapers off to about 2500 Hz, where it takes another step lower.  Definitely not something a human is accustomed to hearing.

73
Chen, W7AY