CREATE TABLE table_50346 ("Callsign" TEXT, "Area served" TEXT, "Band" TEXT, "Freq currently" TEXT, "Purpose" TEXT)

What is the Purpose of the Callsign with a Freq currently of 4rph?
SELECT "Purpose" FROM table_50346 WHERE "Freq currently" = '4rph'
SELECT "Purpose" FROM "table_50346" WHERE "Freq currently" = '4rph'