Kok Chen wrote:
>On Mar 30, 2012, at 9:56 AM, Ed Muns wrote:
>
>
>
>> FSK requires a homebrew or commercial
>>interface and AFSK (with respects to Uncle Bill's history lesson!) requires
>>proper adjustments of drive level, compression off, etc.
>>
>>
>
>I have clarified the AFSK nomenclature with Uncle Bill in private e-mail last
>night.
>
>What most of us today call "AFSK" can rightly be called SSB-AFSK.
>
>Basically, if you take what Bill calls AM-AFSK, remove the AM carrier and one
>of the AM sidebands, you get precisely what we call an RTTY signal (i.e., two
>alternating FSK carries in the RF spectrum). The removal of the carrier and
>one of the AM sidebands from the spectrum is what an SSB transmitter does.
>
>When you plug an audio FSK signal (i.e., two tones in the audio range, for
>example 2125 Hz for Mark and 2295 Hz for space) into an FM transmitter, you
>get what Bill calls FM-AFSK (yes, that nomenclature is quite common). When
>you plug the same audio signal into an AM transmitter and you get AM-AFSK.
>And finally, when you plug the same audio signal into an SSB transmitter and
>you get good old steam RTTY. (It is all in the Convolution Theorem.)
>
>The FM-AFSK and AM-AFSK modes are sub-carrier systems (probably designated as
>F2D emission mode; but I am not 100% certain and I don't *think* that they are
>ham legal in the US below 28 MHz), but "SSB-AFSK" is nothing more or less than
>an F1B emission mode signal.
>
>So folks, at least in my opinion, it is OK to use the term AFSK to describe
>the process of injecting an audio FSK ("AFSK") signal into an SSB transmitter
>to produce RTTY. The pedant might want to call it SSB-AFSK, but it is
>mathematically an AFSK process. I don't mind calling "FM-AFSK" as simply
>"AFSK" either; because it is.
>
>
>
>
That is a very interesting story. It helps explain that defective
equipment will produce defective signals regardless of whether they
begin as FSK or AFSK.
What it does not explain is your 'Dr. Sheldon Cooper' approach to RTTY.
Your seem to have an agenda that requires that everyone agree with your
analysis and your preferred method of generating RTTY signals.
In actuality it is results that count and good results can be had with
either method of generating RTTY signals.
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