[RTTY] the best one ?

[Kok Chen]

My personal recommendation is to keep your current
modem, and front-end it with a Timewave DSP-599zx.

You won't have to change any of your software
configuration.  

You still transmit through the PK-232, and your
software still receives from the PK-232.

You simply place the 599zx between the audio output
of the rig and the audio input of the PK232.

Turn on the Remodulator mode of the 599zx, and you
have a DSP modem.  The Timewave has a DSP demodulator
and has the capability to modulate an internal AFSK
generator, which you feed to an existing modem.

Print seems to be better on the 599zx with marginal
signals than with a couple of other outboard DSP
modems which I have tested it side-by-side against.

The only disadvantage is you may still need a tuning
meter of some sort.  The Timewave's tuning meter is
pretty unusable.  And in Remodulation mode, your
current analog modem's meter will not be showing the
correct reading, either (it will show that you are
always perfectly tuned, HI HI).  I use a homebrew
software tuning tool.

The big advantage of the 599zx is that it has a built
in audio AGC that would help with using more of the
dynamic range of the A/D converter.  With most rigs,
the rig's AGC tapers off at S4 or so.  Signals weaker
than that will not feed optimal audio levels to a
digital modem.

The DSP 599zx also has other features which you may or
may not use -- optimal filters for Amtor, Pactor and PSK31,
CW and adjustable filters if you really have to go use that
voice mode :-).  It also has an audio RMS meter so you
can adjust rig levels, and even a test modulator for
generating RYRYRY for testing the transmitter and other
modems.  It also has headphones output, including a binaural
CW mode which some people find useful for digging out
signals in a pileup (the lower tones are louder in one
ear and the higher tones are louder in the other ear, so
you appear to hear a panorama of CW signals).

A final word on improving your modem.  If you carry it
too far, more and more stations will no longer copy you
while you print them 100%, HI HI.


73 es GL

Chen, AA6TY