i have tried contructing the Simple RC circuit on tony van roon's Electronics page
http://www.uoguelph.ca/~antoon/circ/src.htm

it's appears to simple to be true.
i have tried activating the SCR from audio signal from my computer, but no luck from radio waves.

Anyone have a schematic for this
should i go to the local toy store a rip apart a radio controlled car ?

The cicuit is very primitive, i not recommend for garage-door opening....
It works when sense enough RF energy on tank-circuit frequency.I think this is a demo-circuit,when not work for You, the SCR haven't enough gate-sensitivity. (wrong type) The useful R/C RX-TX pair have coded modulation...

I could never get it to work either.