If you move to FSK modules you can get readily available ones for that price
and even lower, including DSS capable and in some cases protocol embedded so
you don't have to implement many things in SW. Try for instance Si4432
modules from HOPERF (RFM22B or RFM23B). They do everything, including 64
bytes FIFO, manchester, packet recognition, etc.

AM (ask/ook) modules are too unreliable and extremely subject to noise. They
are pretty much unusable in industrial or commercial areas in Europe in my
experience. At the prices FSK modules have today, I don't see a point on
going AM.

2010/5/12 Richard Prosser <rhprosser@gmail.com>

> ivp,
> I have a very basic system running that sends data every 10 minutes or
> so. Each data packet sends the current data and the two previous data
> records. Overall protection is by 8 bit checksum and a record length
> check..
>
> The receiver micro then validates the incoming records as well as
> keeping up to date as to what's been parsed & whats been rejected.
> It works OK but I still miss the occasional record so I'm thinking of
> sending 5 record sets in each packet. As a rough estimate 20% of
> transmissions are rejected.
>
> The code runs on Renasas M16 s so I won't bother to post it, but if
> you do want a copy, just ask. It's pretty basic anyway. (And a bit
> messy).
>
> The RF modules are the cheap $11 433.92 MHz  AM modules from Jaycar..
> The transmission distance is only 6metres or so but through 3 walls.
> Using simple hookup wire "whip" as antennae and in an electrically
> noisy environment.
>
> RP
>
>
> On 12 May 2010 21:00, ivp <joecolquitt@clear.net.nz> wrote:
> >> 433 has two drawbacks you should consider: 1) narrower band
> >> available (which means higher potential for collision with others)
> >> which leads to 2) typically much noisier band as everything is
> >> concentrated in a couple of MHz
> >
> > The modules I'm looking at are pretty basic and don't have
> > channels for either the transmitter or receiver, so it is quite possible
> > that collisions will occur but, as the data isn't urgent, I think I can
> > get around that by coming up with a system to repeat transmissions
> > within some time domain. Still thinking about that
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-- 
Ariel Rocholl
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