"chuck" wrote in message
...
Well, I have a "latency" problem between typing out postings
and engaging my brain; hence the nonsense in my previous two
posts.

Here's what I now think, and I agree with Ralph. AFSK refers
to a type of modulating signal that switches between two
audio frequencies. In other words, the audio frequency is
shifted to key the transmitter. It doesn't mean (as I
suggested earlier) that audio is used to shift the carrier
frequency, although that is the result when you modulate an
SSB transmitter with AFSK tones.

When applied to an AM or FM transmitter, the notion of AFSK
modulation still makes sense. It produces something other
than FSK, of course. But with the proper detection to
recover the modulating tones, there is no reason you
couldn't use AFSK with AM or FM transmitters for RTTY. And
indeed, AFSK is used this way on FM and AM rigs (as someone
has pointed out), although not usually for RTTY.

So the semantics seems to hinge on whether FSK and AFSK
refer to the resulting RF waveform, or to the modulating
signal. The latter notion is broader, and is what I now
understand Ralph was saying.

Thanks, Ralph.

Chuck

Now you seem to be getting what I was trying to say. For example if I feed
a sound card output into my Icom 706 and have it set for AM then a receiver
has to be set up for AM to receive the AFSK I am generating at the RF output
of the rig. Same as for FM.
If I then switch to SSB. I will now be generating FSK at the output of the
transmitter. I can slso put the Icom in the rtty position and feed data
into the data port and it will generate FSK by directly varing the output
frequency. This is the same result as using the mic input to the Icom and
using ssb.

I have not looked at the rules lately but it used not to be leagl to use
AFSK below 50 mhz. That does not mean you can not use a sound card, but you
must have the rig in the SSB position so the resluting transmission will be
FSK.

About 20 years ago I was using a ST-6 into a 220 mhz FM transimtter along
with about 20 others in the local area. By switching the audio leads to the
low band rig, we could also use FSK by running the lowband rigs in the lsb
position.

73 de KU4PT