Properly done, there's no discernable difference between FSK and AFSK. In
general, the difference is that in audioFSK, audio tones are used in SSB
mode to produce MARK and Space tones of 2125 and 2125+170 Hz). In FSK, the
main oscillator is actually shifted between 2 frequencies 170 Hz apart.
However, hardly any (?) new rigs actually shift the oscillator. For
example, the Yaesu FT-1000MP "FSK" mode actually uses an internal tone
generator and thus is -really- AFSK, although offerring the advantages
listed below of FSK mode!
That said, there are still advantages to using "FSK", whether it's "true"
FSK or not. Many older rigs using SSB mode for AFSK won't let you use
narrow filters in that mode. However, they will let you use narrow filters
in FSK mode.
Using AFSK, you need everything set just right, ie you can easily overdrive
the rig with excess audio, producing a lousy, wide signal that might not be
printable and will certainly give you a bad reputation! With more audio
cables etc, using AFSK offers more opportunity for RFI. With FSK, you are
just supplying digital on and off signals to the rig to shift or not shift
the signal, and this is less prone to interference. Since you're not
providing an audio signal, you can't overdrive it.
And finally, my pet peeve, is that if you use AFSK, you will more
likely -not- be on frequency! Most DX spots, skeds, etc are quoted in MARK
frequency. Depending on your rig and its setup, if you're using AFSK, your
dial will be off from the actual MARK frequency by 2125 Hz. Thus when
you're contesting and see a spot for a hot mult at 1408300, you might think
he's not there. However, you might actually find him at
14.081 (14.080875). If you're on the other end and are the one doing the
spotting, people using FSK will not easily find your spots either because
they will be "off" by 2125 Hz. When you're contesting and running down
(up?) the band by clicking on bandmap spots, it's really great when the
signals are actually where they were spotted and where the rig QSYs.
AFSK is great for PSK, MFSK16, SSTV etc, but on RTTY, IMHO real gentlemen
use FSK. HAHA - That's sure to start a controversy! Just kidding! 73 and
have fun!
------------------------------------------------------------
John - WA9ALS - VP5RY (2001)
VP5 photos: http://www.qsl.net/wa9als/vp5ryphotos.htm
email: wa9als@starband.net
homepage: http://www.wa9als.com
----- Original Message -----
From: "Ed" <edw3nr@nexband.com>
To: "RTTY" <rtty@contesting.com>
Sent: Wednesday, April 02, 2003 6:54 PM
Subject: [RTTY] Omni-V and FSK
>
> Just picked up an Omni-V and need some advice for setting up FSK. If I use
> MMTTY it still needs the soundcard for RX. I set the default encoding to
> "Ham" that uses the default normal ham settings for shift and mark/space.
So
> what are the advantages to change to true FSK ?? I can use a PK 232 but
> lack a good terminal program for it. Just a newbie that is a little
> confused. TIA.....73
>
> Ed W3NR
>
>
>
>
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