[RTTY] FT1000MP is FSK.

[Kok Chen <chen@mac.com>]

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).

The microphone and AFSK audio, on the other hand goes through a 
balanced modulator to be translated into RF.

The DDS output also gets mixed with balanced modulators to get to the 
final output frequency, but the mixing is done at constant carrier 
levels and any image is MHz's away, not 2 kc away with AFSK.

(Yaesu engineers must really like the uPC1037H double balanced mixers.  
They are all over the place in the MP!)

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.

73
Chen, W7AY

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