short range low power radio for telemetry

[ben mitch]

hi,

i am toying with the idea of using a small radio transmitter to transmit
one (or two ideally) audio signals over a very short range (no more than
a few metres) to eliminate wiring from a job i am working on. problem:
the power supply for the transmitter would be limited to 3V and around 2
or 3 milliamps. is this possible? SNR would not have to be terribly high.

if so, perhaps someone can point me in the right direction here - can i
expect to find a chip transceiver pair that will do this job off the
shelf, or should i be thinking of building this out of discretes? or
should i be looking for a complete off-the-shelf system? such things exists?

thanks in advance for any comments,

ben

 

[Watson A.Name - \"Watt Su]

"ben mitch" <nnnewsgroup@bbbenmitch.nnnet> wrote in message
news:c50vu9$qa7$1@hermes.shef.ac.uk...

hi,

i am toying with the idea of using a small radio transmitter to
transmit
one (or two ideally) audio signals over a very short range (no more
than
a few metres) to eliminate wiring from a job i am working on. problem:
the power supply for the transmitter would be limited to 3V and around
2
or 3 milliamps. is this possible? SNR would not have to be terribly
high.

if so, perhaps someone can point me in the right direction here - can
i
expect to find a chip transceiver pair that will do this job off the
shelf, or should i be thinking of building this out of discretes? or
should i be looking for a complete off-the-shelf system? such things
exists?

thanks in advance for any comments,

ben

Depends on how much you want to spend. You could use a cheap portable
FM radio as the receiver, with the earphone output connected to a 567
PLL chip for detecting the tones, or even simpler. The transmitter
could be a simple FM wireless microphone circuit minus the microphone,
with two tone generators in place of the microphone. These could be a
555 to generate the tone, passed thru a low pass filter to eliminate the
harmonics.

Or you could just buy a remote and receiver like those used for garage
door openers. These are in the $40 range. See for example this URL
http://www.aaaremotes.com/