CREATE TABLE table_68583 ("Frequency" FLOAT, "Callsign" TEXT, "Brand" TEXT, "Format" TEXT, "City of License" TEXT, "Website" TEXT, "Webcast" TEXT)

Name the lowest frequency for brand of radio manantial
SELECT MIN("Frequency") FROM table_68583 WHERE "Brand" = 'radio manantial'
SELECT MIN("Frequency") FROM "table_68583" WHERE "Brand" = 'radio manantial'