Spawner range.

[Kotja]

What is range of vanilla spawner?

[Curunir]

The Minecraft Wiki is the best resource for questions about vanilla. Here is what it says about Spawners:

 

A monster spawner is only active when a player is within a radius of 16 blocks from the spawner. While the block is active, it will spawn mobs within an 8×2×8 block volume (8 wide and 2 high and 8 long) centered on the center of the block, effectively meaning mobs can spawn in a 9×9 area, or 3.5 blocks from the spawner. Mobs can spawn anywhere in this range that is suitable, with mobs more likely to spawn closer to the spawner than farther away.

Edited January 18, 2015 by Curunir

[Kotja]

So no spawner farm with one grinder.

[Gomo]

You can always create a spawning room for the mobs and redirect them all into one tunnel using water -> kill them all with the grinder at the end of it.

[kla_sch]

You can always create a spawning room for the mobs and redirect them all into one tunnel using water -> kill them all with the grinder at the end of it.

 

I agree, but i suggest  to use conveyor belt instead of water. It's a lot simpler to use:

 

http://wiki.technicpack.net/Conveyor_Belt_%28EU%29

http://wiki.technicpack.net/Conveyor_Belt

 

With belts, you don't need a tunnel. Simply transport them into range of the grinder.