The beacon is at Brasschaat along the Mastenweg.
Arriving at Brasschaat via the N122 go to the west over Beauvoislaan. Immediately after passing Taverne "Den Draver" you turn right into Franseweg. The first road to the right is Mastendreef. The beacon is just past the lake on the LHS of the road.
The top of the beacon was just visible when looking from Franseweg over the lake. You have here a beautiful piece of nature, a nice spot for a picnic.