[Lowfer] Testing Modes

Sun, 30 Nov 2003 18:40:32 -0600

I replied to a message from Dex this afternoon and intended it to go the
reflector as well, but I screwed up. Usually it works the other way, which
can be a bit more embarassing :-) Anyway, I have attached a copy of the
message.

To answer Ed's question about how to use MP3 files -- On many computers,
simply double-clicking on an MP3 file will open one of several available
players. Most Windows computers have "media player" installed. I don't like
it because it is typical "bloatware", but it does the job. The MP3 player I
prefer is a freeware program called Winamp. My copy is several years old, so
I don't know how much garbage has been added to it in the meantime. CoolEdit
will play MP3 files, and so will the excellent freeware graphics program
called IrfanView, if you download and install the "plug-ins". If you succeed
in getting the MP3 file to play, it should be simply a matter of running the
PSK31 decoder program, and selecting the "Wave" input in the *record* mixer.
I don't find an easy way to get to the record mixer settings from DigiPan,
but one technique is to hit the "Windows Start" button on the keypad, then
select "Run", and type in the command "sndvol32.exe -r" (without the
quotes).

I have added the results of decoding the PSK31 message directly from the
original .wav file to my article at
http://www.qsl.net/k0lr/pskvcw/pskvcw.htm

Lyle, K0LR

And here is the message I intended to post to the reflector earlier:

I have been using DigiPan v1.6d, although Dex got better copy with the
MULTIPSK software. I don't think that the version of Digipan I'm using will
read a WAV file directly, and certainly not an MP3 file. I simply "played"
the MP3 file in WINAMP while running DigiPan at the same time (with "Wave"
input selected on the Windows record mixer). Most full-duplex sound cards
will probably allow PSK31 reception while playing back an MP3 or WAV file,
or recording while "transmitting" (which is how the files were created). But
there is a conflict if you try to record while receiving PSK31, so I had to
put the PSK software in transmit mode before trying to record with CoolEdit.

As Stewart pointed out (and I should have realized), the lossy compression
of MP3 makes it more difficult to recover the information buried in the
noise. I should have posted uncompressed WAV files; unfortunately they would
have been 10 times as large. Zipping the files only decreases the size by
about 3 per cent, although I could probably have used 8k samples/second and
cut the file sizes in half. When the uncompressed PSK31 WAV file is played
back in DigiPan, copy is about as good as Dex achieved with MULTIPSK, which
suggests that MULTIPSK would have done even better if it had had a "clean"
file to work with. I'll try running MULTIPSK with the uncompressed file and
include the results in my web article.

The interesting thing is that Dex and Mitch reported good copy using only
the "wetware" between their ears...

Thanks for all the inputs!

Lyle, K0LR

----- Original Message -----
From: "Dexter McIntyre W4DEX" <[email protected]>
To: "WB3ANQ" <[email protected]>; "K�LR" <[email protected]>
Sent: Sunday, November 30, 2003 1:52 PM
Subject: Re: [Lowfer] Testing Modes

> Larry es Lyle,
>
> I can't post to the lowfer reflector because of a new rule qth.net has
> implemented so sending direct to you.
>
> I have never used PSK31 other than to download the program and copy a few
> signals so I have no experience with the mode.  When I tried to get the
program
> to read the file I got the format error.  So I converted the file to a wav
> file.  That's about the extent of my knowledge with Cool Edit also.  Then
the
> PSK program gave me an error message saying it wanted a 8 bit format.  It
took
> me a while to change the file to 8 bit but after doing so the PSK program
did
> take it.  I was able to see some words after doing this but the program
runs in
> high speed!  Like it only takes about 20 seconds for the 3 min file to
read.
> Something needs slowing down and maybe it will decode better but that's as
far
> as I have got for now.
>
> Here's what I have:
>
> http://w4dex.com/temp/LEKpsk31test.jpg
>
> Dex
>
> LarryP WB3ANQ wrote:
>
> > Lyle Koehler wrote:
> >
> > >Well, I wasn't surprised when Dex was the first to copy the CW message,
but
> > >Stewart gets a special award for innovation (and treachery). You guys
amaze
> > >me!
> > >
> > >Lyle, K0LR
> > >
> > >_______________________________________________
> > >>From the Lowfer mailing list
> > >Send messages to: [email protected]
> > >To sub/unsub visit: http://mailman.qth.net/mailman/listinfo/lowfer
> > >
> > >
> > >
> > Lyle,
> >
> > I DLed  the files and also a demo decoder program. The decoder wouldn't
> > accept the mp3 files.
> > So I got a trial version of  cool edit and converted the files to wav
> > files. Not able to decode a thing :-)
> > I would like to know what program everyone is using for PSK31??
> >
> > 73
> >
> > Larry
> >
> > --
> >
> > Larry Putman WB3ANQ FM19rc
> > Pasadena, MD.
> >
> > _______________________________________________
> > >From the Lowfer mailing list
> > Send messages to: [email protected]
> > To sub/unsub visit: http://mailman.qth.net/mailman/listinfo/lowfer
>