ivp wrote:
> 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.

That's really expensive compared to doing it yourself.  One of my customers
makes active RFID tags as part of a indoor location system.  The cheapest
tags contain a PIC 10F202 and a Melexis transmitter.  The end user price is
well under this $11 module price.  The actual volume production cost for a
complete tag is a small fraction of $11.  Of course these tags had to be
seperately FCC qualified as intentional radiators.  That's a hassle, but the
volumes are high enough to make it well worthwhile.

This whole indoor location system works on 434MHz.  The complete lineup of
products includes several flavors of tags and receivers.  Perhaps some of
this already existing hardware would be useful to your application?  There
are a lot of non-obvious things to get wrong the first time you do this
yourself.  These guys have the advantage of being on their second and in
some cases third generation of product, and have already done the dumb
things and put them behind them.

If you explain more about what you're trying to accomplish, I can tell you
whether this existing tested hardware might of use to you.


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