[RTTY] The Problem with AFSK ...

[John Merrill]

The TS-480 also uses "keyed afsk".

John N1JM


On Sat, Jan 19, 2013 at 4:52 PM, Kok Chen <chen at mac.com> wrote:

>
> On Jan 19, 2013, at 3:33 PM, Paul wrote:
>
> > Does anyone know if the FT-1000D is true FSK or is it AFSK?
>
> Keyed AFSK.    Not Direct FSK.
>
> Look for a switch-tail ring counter with a set of resistors that has the
> weight of a sine table :-).  That is the way it appears in the FT-990
> schematics.  The rig clocks the ring counter at different clock frequencies
> to produce Mark and Space tones, and very conveniently, the resistor
> weights produce a phase continuous audio sine wave output.  They change the
> clock frequency to get the different tone pairs (low tone, 2125/2295, etc).
>  Actually quite cleaver of Yaesu engineers.
>
> The follow up FT-1000MP is Direct FSK (using direct digital synthesis VFO).
>
> 73
> Chen, W7AY
>
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