[GreenKeys] RATTS

[Roy Morgan]

At 05:18 PM 2/25/2005, Eugene Hertz wrote:
>Here's a questions I have had for some time and now have the nerve to ask...
>
>If someone were to use a spectrum analyzer to look at a "rtty" signal 
>coming in off the air, would they be able to tell if the signal was 
>generated through ASFK or FSK?

Not if the signal was being well-generated. However, some older methods of 
generating the audio AFSK tones that were applied to the audio input of an 
SSB transmitter caused troubles.  The trouble was other signals transmitted 
besides the desired mark and space carriers.  The source of the troubles 
may have included:
- poor audio tone generation (not low distortion tones)
- bad linearity in the RF sections of the transmitter

One of the books of the 60's/70's (Maybe Byron Kretzman's) talks about the 
trouble some folks got into by using AFSK tones on the HF bands.  AFSK 
audio tones were normally used on VHF because frequency stability of both 
transmitters and receivers was not so hot back then.

It's conceivable that good AFSK operation compared to good rf-level FSK 
could be detected by some fancy analysis of the switching transients and 
wave forms.

Roy


- Roy Morgan, K1LKY since 1959 - Keep 'em Glowing!
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