> 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

One format I have is 1k baud Manchester - a pre-amble followed by
a 2-byte transmitter ID, then data and a checksum. Sent 3 times, once
per second, pretty reliable

> 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

Yes, they're not too bad. I've used the ZW3100/3102 pair a few
times. When possible with a full-wave aerial (69cm), and that goes
about 200m line-of-sight with 5V supply. 1/4 wave will do 100m +
in good conditions

Silicon Chip tested the transmitter for a project and found it works
up to 12V supply, even though the datasheet says 3V nominal. I've
tested the receiver. It's working range is 4.3V to at least 5.5V. My
understanding is that it's being replaced by a more sensitive module

Joe
-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist