Where is the pokeradar on Pokemon Black?

You can't find a Poké Radar in Pokémon Black. The Poké Radar was introduced in Pokémon Diamond, Pearl, and Platinum, and it was also featured in Pokémon HeartGold and SoulSilver.

The Poké Radar is a device used to find Pokémon in specific areas. If you are playing Pokémon Black, you won't be able to use the Poké Radar.