[Elecraft] RTTY FILter

[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 K3's data mode and take advantage of the dual data filters. 

I made this observation while using my Universal "M-8000 Communications
Terminal" 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 coherent butterfly pattern.  The M8000 is connected to
an X/Y oscilloscope.  I use the M8000 Decoder to copy RTTY and SITOR and
it's connected to my K3's line out.  The photos below were taken while I was
copying 45/170 RTTY. 

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/n6756724/DSC01915.jpg 
http://elecraft.365791.n2.nabble.com/file/n6756724/DSC01917.jpg 

-----
Jack WA9FVP
Willco Electronics
--
View this message in context: http://elecraft.365791.n2.nabble.com/RTTY-FILter-tp6756724p6756724.html
Sent from the Elecraft mailing list archive at Nabble.com.