[RTTY] RTTY Rx filter bandwidth

[RLVZ at aol.com]

Wow- a lot of terrific RTTY information on this  Reflector!
 
I agree with Joe that "400 Hz is nearly the minimum bandwidth  necessary 
for proper decoding".  When contesting under heavy QRM condx, I try and try 
and try using the 250hz roofing filter in my  K3 to reduce adjacent channel 
interference and the radio simply does not decode  the average RTTY signal as 
well as  the 400hz roofing filter  does.  By the way, when using the 250hz  
roofing filter I have the DSP filter set to 350hz.  I've  been told that the 
K3's 250hz roofing filter has a bandwidth of aprx. 370 hz...  so I thought 
these 2 settings would provide for maximum selectivity and RTTY  decoding... 
but that simply is not the case as when I switch  over to the 400hz roofing 
filter the copy on the average RTTY signal is  significantly better.  
Perhaps someone has found a  better overall RTTY receive filter combination for 
the K3 than my settings  of: 250hz roofing filter with 350hz DSP filter?  
Such as, perhaps  the 250hz roofing filter with the DSP filter set to 400 or  
450hz? 
 
73,
Dick- K9OM   



400 Hz is nearly the minimum bandwidth necessary for proper  decoding
(minimum intersymbol interference). Narrower filters work by  cutting
adjacent signals more than the desired signal but they impose a  much
higher group delay than a filter that is "flat" across the  necessary
350 to 370 Hz bandwidth.

73,

... Joe,  W4TV