[RTTY] FT-990, MMTTY and the Rascal Mark V+ Interface

[Doug Faunt N6TQS +1-510-655-8604]

Speaking of FT1000 and FT990's, I've also seen hookups that used the
FSK connector for audio out, FSK in, and PTT in, and a RCA connector
to the "patch" input for audio input.  What are the pro's and con's of
doing that?  I don't have these rigs, but have used them occasionally.

73, doug

   Date: Thu, 27 Mar 2003 09:29:16 -0800
   From: Kok Chen <chen at mac.com>

   Hi Paul,

   I have used FSK on both the FT-990 and FT-1000MP (same 4-pin
   connector for the two rigs) but have not used MMTTY, so can at best
   only be half helpful.

   Bear in mind that there are two ways you can transmit a frequency keyed
   RTTY signal.  One is usually termed FSK and the other is termed AFSK.

   FSK is accomplished by keying a single line with a bilevel signal.  The
   two voltages causes the internal AFSK generator in the FT-990
   to produce the Mark and Space offset tones.

   (The FT-990 and 1000, unlike the Ten-Tec Omni, are not "true" FSK rigs,
   even though the connectors are labeled so, and the front panel switch
   say so).

   AFSK is accomplished by passing an audio signal to an SSB (usually LSB)
   transmitter.  The transmitter literally shifts the two audio mark and 
   space
   tones up to the RF region.

   So, AFSK is modulated by an audio signal while FSK is modulated
   by a signal which has two voltage (or current) states.

   That said, the signal you should be therefore be feeding to the pin 
   number
   1 of the 4-pin DIN is a keyed bilevel signal, and the front panel mode 
   switch
   should be set to "FSK."

   If you are outputing an audio signal from a sound card, you should be 
   using
   pin 1 of the 5-pin "Packet" DIN connector, and set your front panel mode
   switch to "PKT."  The latter will give you AFSK on the FT-990.