On Jan 24, 2009, at 10:25 PM, Dave AA6YQ wrote:
> If you're running a soundcard RTTY engine and a hardware modem in
> parallel -- you can get close by clicking on the waterfall and then
> fine
> tune with the XY display, or let the soundcard RTTY engine's AFC
> lock on the
> signal and then click a button that QSYs your transceiver to put the
> hardware modem dead on frequency.
I almost never use narrow filters on RTTY, and only if the nearby
signals exceed the dynamic range of my codec when I am trying to copy
a weak signal among them.
For most of my RTTY work, I click on a waterfall, no AFC. I use a
mouse scroll wheel to fine tune the tone pair if needed, while
watching a crossed ellipse. cocoaModem mixes the input into a
baseband I/Q signal for demodulation, so fine tuning is simply a
matter of changing the frequency of the numerical local oscillator.
S&P inside a pileup with relatively strong signals don't usually
require fine tuning. You can normally click close enough
(cocoaModem's waterfall has a resolution of 2.69 Hz per pixel) by just
clicking.
A second waterfall usually watches the DX from a second receiver. You
have lots of time to fine tune that signal in, and often that is
needed because that signal is usually closer to the noise. Except
during one of the DXpeditions last year where the DX was searching you
out instead of staying fix -- that was where being able to quickly
click on the DX had helped.
In cocoaModem, the mouse scroll wheel will fine tune the tone pair of
either of the two waterfalls that the cursor is hovering over.
73
Chen, W7AY
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