Message-ID: <005501c3c066$c0ac4b60$0401a8c0@vaiosn>
From: "Stewart Nelson" <sn@scgroup.com>
To: rsgb_lf_group@blacksheep.org
References: <28.41604b50.2d0a7870@aol.com>
Date: Thu, 11 Dec 2003 20:16:44 -0800
MIME-Version: 1.0
Subject: LF: Re: Soundcard bandpass filter?
Content-Type: text/plain; charset=iso-8859-1; format=flowed
Content-Transfer-Encoding: 8bit
Sender: <owner-rsgb_lf_group@blacksheep.org>
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org

Hi David and all,

Since you already have .wav files, you just need to process the data
and play it.  Any good audio editor can do that for you.  My favorite
is Cool Edit.  Unfortunately, it was discontinued when Adobe bought
Syntrillium.  However, you can download a free tryout of Audition,
the successor to Cool Edit Pro.
http://www.adobe.com/support/downloads/product.jsp?product=92&platform=Windows

I have never used the Pro version, so the method below may need to
be modified.  The EME signal is easy.  Open it, select the desired
time range, and use Analyze->Frequency Analysis to display an
FFT.  Press Scan to average over the period of interest.  You should
see a clear spectral peak at the CW carrier.  Then, do Transform->
Filters->FFT Filter, select Passive, and draw the desired frequency
response.  Hit Play and listen.  If you don't like the results, you
can undo any number of commands and try again.

Say you have a QRSS30 signal at 800 Hz.  Open it and use Edit->Convert
Sample Type to convert to a low rate, perhaps 2 kHz.  Use the FFT tools
to find the precise carrier.  Filter it with a bandpass about 5 Hz wide.
Use Generate->Tones with the Modulate option to mix with a sine wave
5 Hz below the carrier.  This will give a difference signal at 5 Hz.
Convert Sample Type to 320 Hz, which will remove the sum component.
Now use Edit->Adjust Sample Rate to 48 kHz.  The result will be CW
at 750 Hz and 6 WPM.  The original QRSS need not be strong.  The above
process is averaging for your ears, just as ARGO does for your eyes.

Good luck,

Stewart KK7KA

> Does anyone know of a programme that can produce an audio bandpass filter
> from a soundcard?
>
> I'm trying to find something that will allow me to specify a frequency of
> interest and to have the DSP remove signals above and below two cut-off
> frequencies.
>
> Reason: twofold, 1) I've recently recorded some EME signals from 70cms as
> .wav files and I'm trying to recover reasonable audio.
> 2) It occurs to me that the LF QRSS beacons regularly visible from VO/RU/
> etc. are actually very strong and it should be possible to filter and speed up
a
> stored QRSS file to something like normal CW........just for fun
>
> Would the new 'filter' incorporated into  V2.3 spectrum Lab do this?
>
> Seasons greetings es 73