how far has the signal to travel?
If you could use 446 UHF the antenna will be much smaller, the radios for
that band have CTSS you could be more secure, Or if I were you I would set a
mobile phone and a sound operated switch, ring the phone for say 3 bells
for on 5 for off. Its do able with the sound switch and phone that way only
you have the number, no skip false switching... just a thought. If your in
the UK I can build it in a day or 2.