[WriteLog] What's wrong with AFSK? was - 5 bit mystery unraveled

[Bill Turner]

On Sun, 29 Feb 2004 23:47:51 -0800, Jim Smith wrote:

>It seems to me that the cognoscenti prefer FSK to AFSK.  I have never 
>seen any reasons for this preference, probably because I haven't looked 
>in the right place.  So, what's the problem with just sending AFSK to 
>the radio, thereby eliminating the need for an AFSK to FSK converter?

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When AFSK is done properly, it is indistinguishable from FSK at the
receiver end.  The problem is it can easily get out of adjustment,
mainly by overdriving the audio stages in the transmitter.  When this
happens, the transmitter often outputs the signal at two or more
frequencies.  I often see this during contests.

The other, more minor, problem is the frequency readout of the
transmitter is off by about 2 kHz from the actual frequency being
broadcast.  Again, as long as one is aware of this, it is easily
compensated for.

There is a third problem with AFSK I should mention and that is the use
of the NET function.  IMO, NET should never be used, period.  It is
included in MMTTY and other sound card programs, but invariably causes
more problems than it cures.  Leave both NET and AFC off and tune by
hand.  Once the other station is tuned in, AFC may be turned on if
desired, but modern rigs almost never drift and even AFC is not really
necessary.

In summary, FSK is more goof-proof and is recommended for that reason
alone.

--
73, Bill W6WRT
QSLs via LoTW