Four of Vitec's six biggest shareholders reported buying in February and March filings with Gates' $37-billion Foundation adding 122,200 shares to take a 2.1 per cent stake.
The broadcast systems division of the Vitec Group includes a number of equipment manufacturers including Vinton Radamec, Anton Bauer, Drake, Satchler and Autoscript.
It makes, amongst other things, robotic camera pedestals, wireless teleprompters, tripods, lighting equipment, batteries.
Through the $38.5m acquisition of RF Central in May 2007 it also now produces and sells antennas, receivers and converters for wireless production.
Vitec was founded in 1910 as a movie-camera maker.