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
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