RadioBanter - Sound Card for use with packet radio

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Sound Card for use with packet radio

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. Is there any drawbacks to using a sound card?

Thanks!
Dave

wrote in message
ups.com...
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. Is there any drawbacks to using a sound card?

Depends on what you want to do.
Give us a little more information.
Do you plan to be a router in a tcp/ip network?
Do you wish to run a traditional packet BBS?
Do you want to be able to connect to your local ARES
system to send and receive messages?
Are you interested in APRS? DX Cluster? Chat modes?

--

... Hank

http://home.earthlink.net/~horedson
http://home.earthlink.net/~w0rli

My main interest is in telemetry for various projects, like high
altitude balloons, rockets, etc. APRS is something I'm definately
interested in, but I'd also like to include other data as well. In the
past, I'd used a much simpler (and limiting) position reporting system
and recorded all the flight data on an eeprom for later retrevial. I
don't anticipate monitoring more than one frequency at a time, nor am I
looking to break any speed barriers just yet.

Thanks for the help!
Dave

Sound card packet should work just fine for those applications.

--

... Hank

http://home.earthlink.net/~horedson
http://home.earthlink.net/~w0rli
wrote in message
oups.com...
My main interest is in telemetry for various projects, like high
altitude balloons, rockets, etc. APRS is something I'm definately
interested in, but I'd also like to include other data as well. In the
past, I'd used a much simpler (and limiting) position reporting system
and recorded all the flight data on an eeprom for later retrevial. I
don't anticipate monitoring more than one frequency at a time, nor am I
looking to break any speed barriers just yet.

Thanks for the help!
Dave

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
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

Dave Platt wrote:

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.

I should be able to receive by piping the audio from my radio to the
audio input of the soundcard, right? I wouldn't need a PPT circuit or
anything else unless I wanted to transmit, correct?

Thanks again!
Dave

As a follow up question, what types of digital communication protocols
can a sound card NOT accomodate? I know if can do RTTY, PSK31, etc...
what about PACTOR? MFSK? G-TOR? etc?
Also, is any soundblaster sound card adequate?

Thanks!
Dave

I should be able to receive by piping the audio from my radio to the
audio input of the soundcard, right? I wouldn't need a PPT circuit or
anything else unless I wanted to transmit, correct?

You might be able to manage reception with a simple audio interconnect
cable. The problem with this sort of arrangement is that it's fairly
common for ground loops to exist between the computer and the radio
(one ground through the audio cable shield, another through the
power-line grounding). Ground-voltage differentials can create a
current flow in the loop, which introduces hum on the audio signal,
which could mess up the soundmodem's ability to decode the signal
properly.

A good solution for this is to place a 1:1 audio transformer between
the radio and the computer's sound-card line input. One of the
miniatur "audio coupling" or "audio isolation" transformers will do
the job... it looks as if you can still get these at Radio Shack (part
#273-1374, $3.99) or through many electronics-surplus dealers.

Just cut the audio cable in the middle, solder one half of the cable
to the "primary" winding, the other to the "secondary" winding, and
box it up or pot it in epoxy or wrap it with tape or whatever you
prefer. The transformer will couple the audio frequencies through,
but will not allow ground-loop currents to flow.

The commercial (and better-quality homebrew) PC-to-radio interfaces
usually have two of these transformers (one for receive audio, one for
transmit audio) and an optoisolator for the PTT circuit.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

In article .com,
wrote:

As a follow up question, what types of digital communication protocols
can a sound card NOT accomodate? I know if can do RTTY, PSK31, etc...
what about PACTOR? MFSK? G-TOR? etc?

MFSK is no problem (gMFSK software for Linux, and I'm sure there's
plenty of Windows software available). I believe that PACTOR is also
possible. The newer PACTOR modes are proprietary (or so I understand)
and I don't think there's a freely-available software implementation
yet. I believe that one of the goals behind the SCAMP project is to
create an open-standards (and eventually open-source) protocol with
bandwidth and robustness similar to those of the newer PACTOR variants.

You would not be able to use a soundmodem setup (or a TNC) plugged
into standard radio's audio output port and mic jack, for any digital
mode whose bandwidth exceeds about 2.5 kHz. Some of the newer modes
(e.g. the OFDM multi-carrier system used by Radio Mondial) exceed this
range, and require a different sort of feed arrangement from the radio
(e.g. tapping into or downmixing the final IF to a center frequency of
around 12 kHz).

Also, is any soundblaster sound card adequate?

For many of the simpler modes, I believe that any decent card with
16-bit sample I/O capability will probably suffice.

Some PCs (especially laptops) have only MIC inputs, not LINE inputs -
these would probably require a resistive padder to reduce the radio's
signal levels to those acceptable to a MIC input. Similarly, these
built-in sound interfaces may be "convenience grade" - acceptable for
teleconferencing, but with distortion or noise levels or frequency/phase
response variations too high for certain digital modes.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!