When fighting for that very small increase in S/N ratio that makes the
difference between copy and no copy on a weak cw signal with QSB (not an
unusual occurrence when trying to work 160 m dx from a city lot in
southeastern NM), I have found that an audio filter, with a very narrow
bandwidth, on the output of my Orion can make a difference. Several days
ago I was able to work 3Y0X on 160 m cw. Without the filter I could not
read him.
I am using an old Timewave DSP-59+. Would like something better but I have
not found on the market a really good DSP cw only unit. Am now gathering
the parts for the PLL based design described in the May/June 2005 QEX. In
the meantime I will probably start using the old design APF type that so
many people found helpful in the FT-1000 (after they had modified it
according to the info put out by K1ZM if they didn't have one of the very
early production FT-1000).
Most operators probably will not opt for an audio filter on the Orion
because, among other things, the flexibility inherent in the audio system
would be lost. You pay your money and take your choice.
73 Paul W5DM
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