[Elecraft] Fw: RTTY Questions

[Richard Ferch]

KJ7AE wrote:

> Some questions about keying the K3/KX3 for FSK:

Answers interspersed with your questions below.

> Can someone post a schematic of what this (second) cable looks like
> (connectors, wiring) for the K3?

<http://www.aa5au.com/rttyinterface.html> shows the circuit; what is not 
shown there are the details of how to connect this circuit to specific 
radios. In the case of the K3, the "FSK to radio" (collector of the 
transistor) would be connected to pin 1 of the K3's ACC connector, and 
the circuit ground (emitter of the transistor) would be connected to pin 
5 of the same connector.

> Bonus points for describing it also for
> the KX3, which I have on order...

I believe this is not possible right now. Based on a quick reading of 
the KX3 manual (I may have missed something, of course), it looks to me 
as if the only place where such a connection would be possible on the 
KX3 would be the GPIO (ACC2) connector, and then only if the firmware 
supports using this input for FSK keying (ACC2 IO = FSK?). Note that 
some means to control TX/RX switching (PTT) is also required; using GPIO 
for FSK keying would mean that GPIO was not available for TX/RX control.

> How does the K3 Utility do it with one cable?  Via K3 commands?

Exactly; the K3 utility uses the KY and TB commands to send ASCII text 
to the K3 and manage the contents of the K3's transmit buffer.

> Why don't some of the RTTY programs implement the same thing?

To the best of my knowledge, the K3 and the KX3 are the only 
transceivers available that support the KY command for FSK RTTY (several 
radios support KY for CW keying, but not for RTTY). RTTY software that 
was written for use with other radios (such as MMTTY) uses the serial 
port method, which also works with the K3, so to date there has been no 
outright need and relatively little incentive to implement the KY 
method, except perhaps in software that is specifically written for the K3.

Implementing this method for RTTY is not a simple matter of just issuing 
KY commands for transmitted messages; it also requires polling with the 
TB command, both for buffer management and to determine when messages 
have been fully transmitted to determine when PTT can be turned off. 
Software developers may feel that the benefits to be gained from 
implementing this method do not justify the programming effort.

73,
Rich VE3KI