Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_name_13 ( frequency_mhz INTEGER, city_of_license VARCHAR )

### Question ###
What is average frequency MHZ when is in portales, new mexico?

### Accurate SQL ###

SELECT AVG(frequency_mhz) FROM table_name_13 WHERE city_of_license = "portales, new mexico"