Howdy!

I've touched wireless systems before but not enough to be dangerous. My
background is in software and IPv4.

I have an applicaction in mind for wireless transmission. It would be
very narrow band and low bit rate (obviously), multicast transmission.
The client side is reciever only.

In this case AX.25 is overkill, as none of the collision management is
required. As I understand it, what I need is modem, a radio, and a OSI
Layer 2 frame type suitable for wireless transmission. Would PPP or
HDLC work as a frame type? Is there something better suited to
narrowband wireless?

I don't really understand the actual signal modulation too well. If I
said I wanted to span a particular frequency range, doesn't that
frequency dictate the amount of asynchronous bits than can be modulated
into it? So the modem would have to be tunable right? It would have to
modulate specific to the spectrum in use. So I'm taking it there is a
standard, or do the modems you guys use have a knob to control the
modulation rate? Say the modem buffers 300 bps on the RS232 port but
only has the spectrum to transmit say 200 bps through the radio? Or am
I running into "why the hell would you do that?" territory?

So what the minimum hardware/software required to drop one ip datagram
onto a wire and get it transmitted in say a 10Khz wide band?

-Matt