The homing beacon would not work for the simple fact that if an ennemy unit is within 9'' the homing beacon is destroyed.... So you could have a model at 3.000001'' inch at max of an ennemi with a beacon.
re-read the rule for Homingbeacon
".. Homing beacons are deactivated and removed from the battlefield if an enemy model ends a move within 9" of it."
In your turn their should be (almost none) enemy movement so they could end up within 9", so if you use it up in your own movement pahse you'll have no problems.
Wow! even better than I tought! Thanks! Sorry for the mistake!