CREATE TABLE table_15351 ("Media market name" TEXT, "Callsign" TEXT, "Analog" TEXT, "Digital" TEXT, "Affiliation" TEXT)

what is the callsign for independent affiliation?
SELECT "Callsign" FROM table_15351 WHERE "Affiliation" = 'independent'
SELECT "Callsign" FROM "table_15351" WHERE "Affiliation" = 'independent'