> Well-focussed LEDs are readily available. I tried a bigger lens
> on the transmiter, but the gain was negligible. The big gain with
> a lens comes on the receiver.

JT> Thought about techniques to improve the signal to noise ratio?
JT> Being outdoors isn't a good start with IR.

JT> Is RF a suitable alternative? Some UHF car alarm keys go for
JT> that sort of distance easily. Not directional and quite low
JT> power consumption. 

 UHF is the obvious answer. But then it wouln't be infrared. 

Regards,
Bob

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