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

[Kok Chen]

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.

73 and welcome to RTTY
Chen, W7AY