From Bulbapedia, the community-driven Pokémon encyclopedia.
The Poké Radar (Japanese: ポケモントレーサー Pokémon Tracer, ポケトレ Poké Trace for short) is a key item in Generation IV that is used to seek out wild Pokémon hiding in tall grass.
In Diamond, Pearl, and Platinum
After the player has seen every Pokémon in the Sinnoh Pokédex, they will be able to meet Professor Oak in Professor Rowan's lab in Sandgem Town. After Oak upgrades the Pokédex to the National model, Rowan will give the player the Poké Radar but will not explain it very thoroughly. In Pokémon Platinum the opposite-gender character, Dawn or Lucas, do however - when spoken to they give a practical demonstration on Route 202 if the player has received an Eevee from Bebe in Hearthome City.
It can only be used in the standard tall grass, while on foot, at which point a tune will begin to play, and up to four patches of the long grass may begin to move for a brief period of time (in which the player cannot move). Patches that shake more violently than others are often rarer Pokémon; some Pokémon can only be found using the Poké Radar. When a player walks into a patch of grass that was shaking, a battle with a wild Pokémon will instantly begin. Roaming Pokémon cannot be encountered while using the Poké Radar. Like the Vs. Seeker, the Radar's battery must be charged after use by walking around. It takes fifty steps to fully charge the Poké Radar. It is possible for the Poké Radar to find no wild Pokémon, in which case the message "The grassy patch remained silent..." will be displayed. There is a very rare type of shaking grass that glows white twice rather than shaking. This special kind of grass always holds a Shiny Pokémon.
The game generates up to 4 patches of shaking grass each time the radar is activated. There is potentially one patch of shaking grass in each "ring" of grass around the spot where the player is, up to 4 steps away. Each "ring" consists of all the grass patches that are a certain number of spaces from the player, vertically, horizontally or diagonally. For example, the first "ring" consist of all the patches of grass that are just 1 step from the player, (forming a 3x3 square), the second "ring" are all the patches that are 2 steps from the player (forming a 4x4 square), and so on. It is possible that less than 4 patches of grass are seen shaking. That means that the patch that was selected by the game to shake was not a patch of grass.
The formula for the probability of finding a Shiny Pokémon. Nc is the number of Pokémon in the chain, up to 40. The chances are calculated so that any shaking patch found in or after a chain of 40 has a 1 in 200 probability of being Shiny.
If the Pokémon that is found is knocked out or captured in a Poké Ball, a chain will begin. These chains consist of multiple members of the same Pokémon species encountered one after another. A chain breaks if the player finds a Pokémon other than the one that is being chained, if he/she runs from a battle or if they find any Pokémon outside the shaking grass (even if it is of the same species that is being chained). Therefore, it is recommended that Repel is used in order to ensure this and achieve a higher chain. Entering the patch of shaking grass that is the farthest away from the previous patch of grass (in the fourth "ring" of grass) increases the chances of meeting the same kind of Pokémon consecutively. If, in the middle of a chain, a Pokémon ceases to become available (such as a swarming Pokémon), that Pokémon will continue to be available until the chain is broken. The player can "reset" the radar in the middle of the chain without breaking it, simply by recharging the radar and avoiding the current grass patches that have Pokémon in them. When activated again, the radar will generate new patches and the old ones become normal grass patches.
The chance of finding a Shiny Pokémon patch increases the longer the chain is. This chance maxes out at chain #40, in which the chance of finding a shiny grass patch is 1/200, a substantial increase from the usual 1/8192. Furthermore, the shiny grass patch always contains the Pokémon that is being chained, so there is no risk of breaking the chain when entering one. A Shiny Pokémon can appear in a normal grass patch, however, but the chances of that happening are the same as normal.
One of the many functions of the Pokétch is to display the current chain and the three best chains made so far.
List of Radar-exclusive Pokémon
In HeartGold and SoulSilver
- Main article: Pokéwalker
On the Pokéwalker that is bundled with Pokémon HeartGold and SoulSilver Versions there is a primitive version of the Poké Radar, which costs 10 Watts to use. In this Poké Radar, there are four patches of grass, one of which will display a '!' which indicates the presence of a wild Pokémon (or a '!!' or '!!!' depending on the Pokémon's rarity). As with chaining in the main series games, chaining is also possible in the Pokéwalker, but it is dependent on timing and the amount of steps taken. If the player waits a while after a '!' appears and click it, there is a chance that he/she may get another '!' patch, over-riding the previous one. If the player continues this trend he/she will get a '!!' patch , and then a '!!!' patch after that. The timing needed to wait seems to vary between the rarity of the Pokémon, with rarer Pokémon needing less time.
In the TCG
The following is a list of cards named Poké Radar.
On Bulbagarden forums