On Jul 26, 2011, at 12:47 PM, Terry Dunlap wrote:
> Does it take two sound cards to use CWSkimmer and MMTTY (or whatever
> you're using for RTTY)?
To receive both DX and pileup concurrently, you just need a single stereo sound
card and one program, if you have the right program.
See here:
http://www.w7ay.net/site/Applications/cocoaModem/UsersManual/RTTYPage/WidebandRTTY/WidebandRTTY.html#widebandrx
If you scroll down to the first Figure (called Figure 11 because this page was
cut from a much larger earlier page :-) you will see a window with two
identical receive section that share a single transmit interface.
Further down, in Figure 12, you can see what one active receiver section looks
like.
In cocoaModem, either modem can select any sound card. The two receive
sections can actually look at the same passband (i.e., to decode two different
signals within the same 2.4 kHz passband) by selecting the same sound card.
Or, one receiver can watch the left channel of a sound card and the other
receiver watching the right channel of a sound card. Or, the two receivers can
be connected to two completely different sound card with different sampling
rates.
Each receiver has its own waterfall and its own crossed ellipse indicator.
(A little further down from figure 12, there is a short description of the RTTY
click buffer.)
Regarding crossed ellipse displays, the non-waterfall mode in cocoaModem has a
much fatter crossed bananas. See
http://www.w7ay.net/site/Applications/cocoaModem/UsersManual/RTTYPage/BasicRTTY/BasicRTTY.html#basictuning
Since the non-waterfall version assumes that you tune using the VFO knob, the
wide bananas' bandwidth is much better at telling you which direction to tune
when you are off tuned by a lot when you start.
With a waterfall, you can click quite closely to start with and the crossed
bananas really only serves the purpose to fine tuning (cocoaModem uses the
mouse scroll wheel or the Griffin PowerMate knob to fine tune). Precise tuning
helps with the really weak signals.
Anyway, cocoaModem is just a fun project that I started many years ago to play
with digital modes. Before the two waterfall demodulator, cocoaModem had the
"dual RTTY" demodulator shown here:
http://www.w7ay.net/site/Applications/cocoaModem/UsersManual/RTTYPage/DualRTTY/DualRTTY.html
In that case, there is only a single "panadapter" which you can switch between
the "main" or "sub" receiver sound card. It is OK most of the time since the
DX seldom QSY. But the first two Ducie RTTY operations where the same JA op
kept moving had caused me to think that I need an interface where you can watch
both receiver's spectrum. Waterfall tuning really shines when the DX keeps
moving. You can find him even before the VFO twiddler even notices that the DX
has not issued a CQ for some time :-).
(I am sure many RTTY folks would rather forget the Ducie fiascos. It even led
our usually gentlemanly AA5AU to mock the operation with a web page -- was it
Parody Island or something like that? Newer RTTY ops missed out on the barrel
full of chuckles we all had here. :-)
There are other cases of unintended QSY, like when Trey N5KO was operating from
Thule or South Georgia, I think (over heating rig, if memory serves). Like
being able to quickly switch from 45.45 baud to 50 baud, you won't need it to
worry about QSYing DX too often. But when you need it, you really need it, as
many who tried to work P5/4L4FN found out. Ed really cleared the spectrum for
the peanut whistles to get through when he switched over to 50 baud :-).
73
Chen, W7AY
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