[Discuss-gnuradio] cheap receivers

[Raphael Clifford]

I am starting a project to broadcast data to display terminals in 
Africa.  I need long distances (>100 miles) and *really* cheap 
receivers.  As I am new to this please forgive my ignorance but I don't 
understand a few things.

It seems to me that the cheapest way to build a receiver is to wire a 
standard AM radio to your computer. The two options are through the 
standard audio out and modifying a radio to bring out a connection to 
the Narrowband discriminator.  So my questions are

1) I am not at all clear what the advantage of the latter technique is 
in terms of bandwidth.  Can anyone tell me? As far as I can tell you get 
frequencies in the range 300-3000Hz from the audio output and 0-3000Hz 
from the discriminator so there is only a marginal gain.  However, I am 
very much a newbie.  Is there are significant increase in the quality of 
the signal from the discriminator at all frequencies?
2) Can the output of both techniques be decoded in software without any 
further hardware?  I can't afford to spend money on dedicated hardware 
for the receivers.
3) Is this approach of using an AM radio a stupid one in the first 
place? Is there a much better way?
4) What should I read to bring myself up to date on the issues involved? 
 For example, how would I calculate the expected bandwidth from 
different frequencies/coding techniques etc.?

Cheers,
Raphael