K3 Question: AFSK-A or DATA-A for RTTY?

[James Bennett]

I've been a PSK31 user just about ever since the mode came to be. Not a heavy user, but couple time a month I get on and have some nice keyboard QSO's. In the 50 years that I've been licensed, I have NEVER made a RTTY QSO! However, it does intrigue me so I started messing with it a little this week.

I recently got a new external sound card for my station - a Tascam US125. It is connected to my iMac via USB and the K3 via a pair of stereo cables. Works fine on JT65, JT9, and PSK31. I use WSJT-X for the JT-modes and cocoaModem (CM) for PSK31. CM also provides RTTY so I gave it a shot. After a few burps I got it going.

With PSK31 and the JT-modes, I've always had the K3 in DATA-A setting. RTTY "seems" to work in either DATA-A or AFSK-A. Fred Cady's K3 book states that AFSK-A is "optimized for RTTY". How? What is the real benefit to switching to AFSK-A mode for RTTY? Is that what everyone is using, or is DATA-A just as good?

Thanks, Jim / W6JHB
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[Bill Frantz]

I find myself switching between Data A and AFSK-A quite a bit.
The RTTY dual passband DSP filter (DUAL PB) can help a lot with
QRM from nearby RTTY signals, and it eliminates much of the
off-frequency noise. You can also turn on TEXT DEC to get the K3
to decode the RTTY, giving you another chance with weak signals.

With cocoaModem I am always using the RTTY, rather than the
Wideband RTTY or Dual RTTY options. The crossed loop tuning aid
can't be beat. It simulates the CRT based tuning indicators used
with hardware RTTY receivers.

73 Bill AE6JV

On 9/15/14 at 7:07 PM, [hidden email] (James Bennett) wrote:

>With PSK31 and the JT-modes, I've always had the K3 in DATA-A
>setting. RTTY "seems" to work in either DATA-A or AFSK-A. Fred
>Cady's K3 book states that AFSK-A is "optimized for RTTY". How?
>What is the real benefit to switching to AFSK-A mode for RTTY?
>Is that what everyone is using, or is DATA-A just as good?
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[Don Wilhelm-4]

Jim, and all,

Yes, the AFSK A data submode is optimized for RTTY operation.  The
default sideband is LSB and the use of the dual filter is possible.
Furthermore, the K3 dial display shows the mark frequency.
If you are using an RTTY mode with an application such as MMTTY, you
will find the AFSK A mode useful and tuning will be done using the K3 VFO.

OTOH, if you are using an application that has a waterfall display and
does point and click on the preferred signal (rather than tuning to the
signal with the K3 VFO), then the use of DATA A in reverse mode will
likely be more useful to you for RTTY - your application may switch
sidebands when RTTY is selected - check the documentation for your
application, it is a 'mixed bag' and some application 'do it right'
without explicit actions by the user while others will require that LSB
be explicitly selected.  The frequency display on the waterfall is also
application dependent.  Refer to the application documentation to assist
in understanding what is being displayed on both the transceiver
frequency display and on the waterfall.

For data modes other than RTTY, yes, DATA A should be used - it all
depends on the data mode application.

73,
Don W3FPR

On 9/15/2014 10:07 PM, James Bennett wrote:
> I've been a PSK31 user just about ever since the mode came to be. Not a heavy user, but couple time a month I get on and have some nice keyboard QSO's. In the 50 years that I've been licensed, I have NEVER made a RTTY QSO! However, it does intrigue me so I started messing with it a little this week.
>
> I recently got a new external sound card for my station - a Tascam US125. It is connected to my iMac via USB and the K3 via a pair of stereo cables. Works fine on JT65, JT9, and PSK31. I use WSJT-X for the JT-modes and cocoaModem (CM) for PSK31. CM also provides RTTY so I gave it a shot. After a few burps I got it going.
>
> With PSK31 and the JT-modes, I've always had the K3 in DATA-A setting. RTTY "seems" to work in either DATA-A or AFSK-A. Fred Cady's K3 book states that AFSK-A is "optimized for RTTY". How? What is the real benefit to switching to AFSK-A mode for RTTY? Is that what everyone is using, or is DATA-A just as good?
>
>

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[Jim Brown-10]

On Mon,9/15/2014 8:46 PM, Don Wilhelm wrote:
> Yes, the AFSK A data submode is optimized for RTTY operation.  The
> default sideband is LSB and the use of the dual filter is possible.
> Furthermore, the K3 dial display shows the mark frequency.
> If you are using an RTTY mode with an application such as MMTTY, you
> will find the AFSK A mode useful and tuning will be done using the K3
> VFO.

Yes, AFSK A is the way to go, and it works very well with VOX! Note also
that in the last year or two, "authorities" say the dual passband and
narrow filters are a bad idea, and recommend 400 Hz bandwidth IF. The
problem with dual passband and narrow filters is phase shift, which
degrades decoding. Many top RTTY contesters have taken that advice.

73, Jim K9YC
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[Jim Brown-10]

On Mon,9/15/2014 7:07 PM, James Bennett wrote:
> What is the real benefit to switching to AFSK-A mode for RTTY? Is that what everyone is using, or is DATA-A just as good?

Hi Jim,

I read other folks responses without seeing your original post. Sorry  
about that. To use AFSK, you need a single decoder program like MMTTY
that operates much like you would on CW and SSB, tuning up and down the
bands with a narrow-band receiver. This is the standard for contesting
and DXing, and it permits the RX to be very narrow, so that it is much
less bothered by QRM. DATA-A is for multi-decoder programs like you have
been using, and you may find it more satisfactory for general use in the
same way you use WSJT-X and PSK31 software. Or maybe not. The major
difference between RTTY and other digital modes is that there are no
standard dial frequencies like there are for JT65, JT9, and PSK31. RTTY
ops generally range all over the band, especially during contests, and
also for DX operations.

So the best answer to your question is that DATA-A is for "dial
frequency" operation like JT65 and PSK31, whereas AFSK-A is for tuning
up and down like a CW op.

73, Jim K9YC
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