[Elecraft] RTTY Filters

[wa9fvp]

Sometimes in the evenings I like to copy WLO broadcasting news and weather
using RTTY and SITOR mode B the frequency is 8.475.225 LSB.  I decided to
use the data mode and take advantage of the dual data filters in the K3.

I made this observation while using my Universal M-8000 with the Butterfly
filter installed. The Butterfly filter is a perfect filter for demodulating
RTTY.  It uses a combination of bandpass and notch to generate a butterfly
pattern using an XY oscilloscope.   When I copy WLO using LSB (the width
control is set to 450Hz and with an I.F. offset of 2.25 I get a perfect
butterfly pattern.  When I switch to DATA mode using the dual filters the
Butterfly pattern is distorted with non coherent phase shifts and in the
noisy conditions the copy degrades.
http://elecraft.365791.n2.nabble.com/file/n6755974/DSC01915.jpg 
http://elecraft.365791.n2.nabble.com/file/n6755974/DSC01917.jpg 

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Jack WA9FVP
Willco Electronics
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