When vista radio is the owner how many call signs are there?
CREATE TABLE table_18536769_1 (call_sign VARCHAR, owner VARCHAR)
SELECT COUNT(call_sign) FROM table_18536769_1 WHERE owner = "Vista Radio"
### Context: CREATE TABLE table_18536769_1 (call_sign VARCHAR, owner VARCHAR) ### Question: When vista radio is the owner how many call signs are there? ### Answer: SELECT COUNT(call_sign) FROM table_18536769_1 WHERE owner = "Vista Radio"