user: Question: What's the highest frequency of the KBDR callsign?
Columns: ['Frequency', 'Callsign', 'Brand', 'Format', 'City of License', 'Website', 'Webcast']
Types: ['real', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: [88.1, 'KHOY', 'Catholic Radio', 'Religious', 'Laredo', 'khoy.org', 'listen live']
SQL:

assistant: SELECT MAX("Frequency") FROM "Table" WHERE "Callsign" = 'KBDR';