Soundcard Modem

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Soundcard Modem

Postby bartkindt » March 15th, 2009, 9:08 pm


I just downloaded the Wave Audio package 1.89. It looks great.

Reason I downloaded it is, I need to build an Modem based on incoming data on the microphone input of the sound card.
This means, a 1200 Bps data stream (from a radio) in inserted in the microphone input of the card.
It consist of two switched tones, 1200 Hz and 2200 Hz. The one represents a Bit 0, the other a Bit 1.

I need to filter these two tones out of any other noise which comes with it;
Then I need to see which tone is transmitted and calculate the lenght of each;
Then I have to synchonise to the incoming 1200 Bps data;
Then I have to build Bytes out of the Bits;
Then I have to recombine the actual data packet.

How do I go about this? Even a start of how to 'listen' to the two incoming tones and how to 'filter' them out would be great.


Bart Kindt
New Zealand
Posts: 1
Joined: March 15th, 2009, 7:19 pm

Re: Soundcard Modem

Postby cozturk » March 25th, 2009, 9:39 pm

Tone decoder component

TrueTTY or smilar software for Radio decoding
Posts: 63
Joined: June 30th, 2005, 5:39 am
Location: Istanbul - Turkiye

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