[Elecraft] RTTY via FSK-D

[Joe Subich, W4TV]

> MMTTY used to send upside down in FSK and there was no way to 
> change it via software.

MMTTY does not "send upside down."  It generates a "1" (high) on 
the output of the UART for mark which is correct.  Most interfaces 
use a simple NPN transistor which turns that "1" into a closed 
contact (again correct for the old 60 mA "loop" circuits).  

Unfortunately, many rigs expect the FSK input to be OPEN (or 
high due to their internal pull-up) for Mark.  The user needs 
to read his transceiver manual and if it is normally "mark open" 
or "mark High", select "REV" in the menu ... this applies to 
such a diverse group of transceivers as the FT-1000D, FT-1000MP, 
IC-706mkIIg, TS-870, etc.  

Again, MMTTY is not "upside down" ... it is the interface 
standards that are still rooted in the 60 mA current loop 
instead of the data communications world where Mark=1/Space=0.  

73, 

   ... Joe, W4TV 
 


> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net 
> [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Brian Alsop
> Sent: Thursday, March 04, 2010 10:12 AM
> To: Dave Hachadorian
> Cc: Elecraft Reflector
> Subject: Re: [Elecraft] RTTY via FSK-D
> 
> 
> Comment on the FSK circuit.
> MMTTY used to send upside down in FSK and there was no way to 
> change it 
> via software.
> It is possible the circuit may have to be modified to invert 
> the polarity.
> 
> 73 de Brian/K3KO
> 
> Dave Hachadorian wrote:
> > Comments interspersed.
> > 
> > Dave Hachadorian, K6LL
> > Yuma, AZ
> > 
> > --------------------------------------------------
> > From: "Brett Howard" <brett at livecomputers.com>
> > Sent: Thursday, March 04, 2010 1:11 AM
> > To: <elecraft at mailman.qth.net>
> > Subject: [Elecraft] RTTY via FSK-D
> > 
> >> So I'm thinking about wiring up the FSK IN pin on the AUX
> >> connector to
> >> do RTTY TX "properly".  I'm curious of a few things before I 
> >> take the
> >> time to make the cable.
> >>
> >> First off how do people usually drive this signal?  I assume
> >> its usually
> >> taken off of a serial port...
> > 
> > 
> > Yes, circuit is shown here: http://www.aa5au.com/rttyinterface.html
> > 
> > 
> > 
> > 
> >  I've tried a few RTTY apps and I've
> >> gotten them all to work via AFSK and all seem to have their
> >> pros/cons.
> >> I have a feeling in the end that I'll probably most use MMTTY 
> >> being that
> >> it has a very nice interface into N1MM (unless there is another
> >> application that has a nice interface into N1MM that I should 
> >> be aware
> >> of).
> > 
> > 
> > MMTTY is the way to go.
> > 
> > 
> >> Finally my last question is that if this comes off of a UART
> >> how has the
> >> timing been for people?
> > 
> > 
> > The timing is solid.
> > 
> >  
> > 
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