Why is my mob spawner not working - Where should I be idling?

I made my mob farm at height 200 and the collection area is on 70
There is no mob spawning, so where should I be idling so I get highest mob spawning rates as possible? I attempted to idle at the collection area but no mobs spawned so I presume I need to be closer? What is the maximum distance from the mob spawner that it'll still work?
Best Answer
Your idle area is 130 blocks from the mob spawner, which is just over the 128 block radius from the player outside of which mobs will not spawn:
You should move your idle area up to at least level 72 if you want to see any spawns at all, but I'd recommend having the idle area at y level 175 if you want to reduce the number of mobs despawning.
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Where is the best place to AFK for a mob spawner?
Your AFK room can technically be anywhere within 128 blocks of the spawner room. But the best place to put it is high up into the air, approximately 80 blocks above the roof of the farm. Since mobs can't spawn in midair, going this far into the sky makes your spawner room the only place they can possibly appear.How far away should you AFK from a mob spawner?
In the case of a spawner, players need to be at a distance of at least 16 blocks distance from the spawner to activate it. When AFK-ing at a spawner-based farm, players should be at a distance of less than 16 blocks from the spawner.How close to a spawner do you have to be to activate it?
A spawner activates when a player comes within a spherical radius of 16 blocks from the center point of the block; i.e. 15.5 blocks from the spawner itself.If Your Mob Grinder Isn't Working, Watch This!
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Images: Pew Nguyen, Yan Krukov, Yan Krukov, Mikhail Nilov