[TenTec] OMNI VI Plus, MMTTY, and FSK

[KA5M@aol.com]

I used the FSK keying circuit specifically for the OMNI VI Plus shown on 
http://www.aa5au.com/rttyinterface.html to build a COMM port to radio interface.  
I used a 2N4402 PNP transistor.  As shown, pin 3 (TXD) of the DB9 comm port 
goes through a 1K resistor to the emitter.  The base is grounded, and the 
collector goes to Mark/Space on the rear of the OMNI VI Plus. When I try to transmit 
RTTY, all I get is a steady tone.  The radio is not being keyed.  (PTT using 
a 2N4401 NPN transistor work fine, no problem.)

Has anyone built their own transistor FSK and PTT interface and got it to 
work?  Any suggestions would be appreciated.

73,
KA5M, Marsh