Re: [RTTY] FT1000MP is FSK.

["Ian White, G3SEK" <G3SEK@ifwtech.co.uk>]

Kok Chen wrote:
> My mistake for saying the FT1000MP is not direct FSK -- it is.  Thanks 
> to Ian, G3SEK for pointing it out to me.
>
> I just got back to the home QTH so I could check the schematics.  The 
> FSK keying signal of the MP (original MP, not the Mark V) goes directly 
> to the CPU and from there to the local RF DDS (digital synthesizer).

> On the other hand, the FT-990's FSK keying signal does go though an 
> independent AFSK generator (and there is a pot for adjusting the audio 
> level on the way to the balanced modulator).
>
> So, bottom line: FT-990 is keyed-FSK (i.e., internally AFSK) and 
> FT-1000MP is FSK.

It also seems likely that the Mark V and the MkV Field also generate 
true FSK in the same way, by directly programming the carrier DDS... but 
please can owners of these rigs confirm from the detailed schematics? 
Look for a module labeled "CAR DDS" near the center of the schematic for 
the AF board. If it's there, the MkV and Field will be true FSK like the 
original MP.

The detailed schematics seem to be the only level of information we can 
trust, short of eyeballing the actual AF boards of these rigs, so 
someone please confirm!

We now know that the RTTY information in the original MP User Manual 
contains too much cut-and-paste from the manuals for older models. The 
instructions in the original MP manual about adjusting the MIC gain 
control in FSK mode are not valid - and the MIC gain control does 
nothing in reality either.  These instructions are gone from the MkV 
User Manual.

Now the not-so-good news: tuning away from my MP's FSK signal on a 
second receiver, the keying transitions sound harder (and spread wider) 
than I'd like. If it generates FSK by directly programming the carrier 
DDS, how the heck can we soften the keying transitions?



--
73 from Ian G3SEK
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