MC3418: Anyone converting analog audio to digital?

[mbramwel]

I would like to transmit digital audio via radio. I have the radio side sorted out ok. I have a transciever that is capable of 9600 data via the discriminator (RX) and direct drive (TX).

My guess is to use something like the MC3418 to encode the audio into a digital signal that can be feed into my transmitter.

I do not know where to find such a chip in canada. Maybe another delta modulator exists or a better (still inexpensive) way of doing it.

Maybe I should buy a $20 GE cordless phone and see what I can remove from the device.

Any one doing something like this? Any ideas?

 

[Nigel Goodwin]

9600 baud is FAR too low for sending audio, it's only 960 bytes per second, so it's audio bandwidth would only be a couple of hundred hertz.

Assuming you're using licence free radio modules, the licence free conditions usually ban audio usage as well!.

 

[mbramwel]

The required baud rate is dependant on the encoding method. 9600 baud should be adequate for voice grade communications. The MC3418 actually suggests this in their application notes.

I work at a University and the radios are licensed for experimental use. Any mode is permitted. I'll probably use a 5khz voice channel although North America is moving towards tighter channel spacing for land mobile. Most of the newer kit seems to be 2.5/3khz wide.

I found someone that used the MC3418 and pushed their voice up a submersible cable at 9600baud with telemetry data.