[amsat-bb] Re: Looking for polynomials

[Robert McGwier <rwmcgwier@xxxxxxxx>]

>At 11:50 PM 07/20/2000 Thursday, you wrote:
>
>>In both FSK and AFSK, the data modulating the signal is digital data.  Both
>>modes are digital modes.  It's just that in the AFSK situation you are
>>applying the modulated data at the audio stage in the transmitter while at
>>the FSK end of things you modulate the RF signal at one of the RF stages.
>>Either way as the signal gets mixed up to the final RF output frequency, the
>>RF signal is Frequency Modulated according to the signal applied earlier.
>
>Hmmm, I have always modulated an audio stage for FSK (9600 bps).  I have
>also always modulated an audio stage with AFSK.    The difference is
>that in the case of FSK, it is the baseband analog waveform, the smoothed
>(filtered)   DATA that modulates (admittedly a later) audio stage.  In AFSK,
>the modem, modulates a TONE, with this same baseband analog waveform
>and <<THEN>> this already modulated tone is used to FM modulate an
>FM transmitter.  The problem with AFSK is that you have to do TWO detections.
>One to do the FM detection, and then another detection to on the audio to
>get to data.  This is two harsh nonlinear processes, two threshold effects,
>etc. etc. to deal with.    As a communications professional, let me assure
>you without proof and make an argument from authority rather than technical
>analysis,  AFSK SUX.
>
>Bob
>
>
>
>>So FSK and AFSK aren't all that far apart.
>>
>>I think your tests show very clearly that the link budget with a 9600 baud
>>data link is far less than with a 1200 baud link.  The fact that with a
>>crude measurement setup you got very close to the theoretical value tells me
>>you did a good job.
>>
>>73,
>>
>>Jon
>>NA9D
>>
>>-------------------------------------
>>Jon Ogden
>>NA9D (ex: KE9NA)
>>
>>Member:  ARRL, AMSAT, DXCC, NRA
>>
>>http://www.qsl.net/ke9na
>>
>>"A life lived in fear is a life half lived."
>>
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>
>


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