[Elecraft] K3s AFSK frequencies

[Mike Dodd]

Hello to the group. I just put my new K3s/100 into service, and have a 
question about the Mark frequency to use with AFSK. Before the K3s, I 
used a SignaLink with my KX3 and MMTTY. With that setup, I set MMTTY to 
use 915 Hz for the Mark frequency, and everything worked fine.

Fiddling with the K3s and its internal USB sound card (I love that!), I 
can select various higher Mark frequencies using the PITCH button, and 
set MMTTY accordingly, and the K3 still decodes the RTTY.

So my question is, what is the "standard" or common Mark frequency to 
use for AFSK on the K3? Or is it a matter of personal preference -- 
which sounds better to my ears when tuning RTTY signals?

Also, what bandwidth is commonly used for 170 Hz-shift RTTY? I stocked 
this K3s with four 8-pole filters, including 400 Hz and 250 Hz. The 250 
Hz filter works with RTTY, but the MMTTY X-Y scope pattern looks like I 
might be pushing things with that narrow a filter. the 400 Hz filter 
looks better.

But David (I think) at Elecraft told me when I made my list of filters 
that I'd be using 2.1 kHz or 2.8 kHz for RTTY. That doesn't make a lot 
of sense to me if QRM is present. OTOH, MMTTY is decoding specific 
tones, so maybe filter width doesn't make much difference.

What do the experts say?

Thanks for any information.

-- 
73, Mike N4CF
Louisa County, VA USA
Elecraft K3s/100
Carolina Windom up 45'
http://n4cf.mdodd.com