Is using a sound card as effective as a TNC for packet radio? I
imagine this may depend on the software, but I'm debating on which to
get.

I think you're probably right - the quality of the software is going
to make the biggest difference. There's probably more spread _within_
each category (soundmodems vs. IC-based or discrete "hard" modems)
than there is between categories.

One advantage to using a sound modem is that you can, in principle,
run two or more modems on the same soundcard at the same time... e.g.
1200 AFSK and 9600 FSK. You can also experiment with new digital
modes (e.g. PSK31, SCAMP) which either aren't supported in "hard" TNCs
or which are expensive in a hardware implementation.

Is there any drawbacks to using a sound card?

You can burn up quite a lot of CPU cycles (which adds up to power
consumption and heat in your system) running the DSP software to
implement a soundmodem. You'll need an operating system which can
keep the soundmodem running reliably ("soft" realtime behavior) even
in the face of whatever other CPU and disk I/O workload you put on
your computer.

You ought to be able to put together a basic 1200 AFSK setup with
either a soundmodem (kluge together an audio isolator / PTT circuit,
or buy a RigBlaster or RASCAL), or with a real TNC (e.g. a TNC-2 or
clone - pick up a used one for a song at a local hamfest/fleamarket)
quite inexpensively.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
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