-----Original Message-----
From: Jerry Pixton <jpixton@shentel.net>
To: wl-users@wu3v.net <wl-users@wu3v.net>
To: <writelog@contesting.com>
Date: Friday, April 16, 1999 8:41 AM
Subject: [WL-USERS] psk31 trace colors
>So what do the green trace and the gray trace tell me. Dick note says the
>green trace dipping indicates idle signal (no data). Is there more meaning?
>Is this the frequency spectrum of the in phase and 180 degrees signals?
>
>Jerry W6IHG
>------------------------------------------
>Dr. Jerry R. Pixton, PIXOS Designs
>http://www.pixos.com/designs/
>jpixton@shentel.net
>------------------------------------------
The green trace is the spectrum of the received signal centered
on your transmit frequency and going +/-250Hz from there. In
the freeware software, the FFT is centered on the receive
frequency. I think the transmit frequency is a better origin.
The gray trace is just the green trace, but low pass filtered. The idea
was that the gray trace represents the "history" of spectrum like
the waterfall. But its not clear this is an improvement over the
waterfall display.
The dip in the center of the spectrum of an idle signal is a
characteristic of the PSK31 signal itself. When it is idling, the
signal is exactly the multiplication of a 16 Hz cosine and a pure
tone. The spectrum of such a signal is two peaks at +/- 16Hz
from the center of the pure tone and (paradoxically) the pure
tone itself does not appear in the spectrum.
Wayne, W5XD
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