| I asked this question of a fair few people before buying and it seems that most of the time the trackside beacons are left switched on and are on the pit wall (or very close). So I didn't bother buying one, but I do know where I can borrow one if needed.
The best tip I got though was to set the blanking corectly in case another rider had a beacon setup elsewhere on the circuit for split times etc. | 
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