Posted by
P.B. Christensen on
Oct 26, 2010; 3:12am
URL: http://elecraft.85.s1.nabble.com/APF-For-K3-tp5671688p5673249.html
> There's a button labeled "RIT" and an associated knob especially for that
> purpose.
Wes,
Here's an example of using APF in conjunction with RIT. I normally leave my
CW offset at 650 Hz. Some of my CW operating is very weak signal DX on the
low bands. When copying extremely weak DX in the midst of static crashes, I
need to temporarily shift pitch to less than 400 Hz. Some ops, including
W4ZV, have noted that weak CW copy can improve when low pitch is used. I
also don't want to tamper with my normal CW offset if I don't need to.
By engaging in RIT, I would like to temporally dip the incoming pitch, leave
my CW offset alone where I want it 95% of the time, and then adjust the
frequency of the APF to match/peak the incoming pitch selected by RIT. If I
want to experiment with different pitch settings based on band conditions, I
also want the ability for the APF peak to track the pitch I've selected on
RIT. That requires a tunable APF. This is precisely what the FT-1000/D
gave its users.
Of course, the greater the departure of the RIT pitch from the offset may
require a wider DSP filter setting and/or roofing filter. But under these
weak band conditions, wide DSP and roofing filters are just fine when band
activity and adjacent interference is low or moderate. When I'm working
early morning grayline DX on 80m or 40m, I rarely encounter strong adjacent
stations since conditions are long and stateside is not heard much of the
time. Because of this, my overall Rx bandwidth is generally set to 2.8 kHz
or greater. Even when weak DX is running split and listening up 2 kHz,
there's ample separation to allow a filter settings wide enough to depart a
few hundred Hz from the CW offset.
Paul, W9AC
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