The invention provides a method of adjusting a principal communication direction of a steerable directional antenna for communicating with a terrestrial electromagnetic signal source, the method comprising: providing location specific steering data comprising one or more steering data portions, each of the steering data portions being specific to a respective location; determining a location of the steerable directional antenna; selecting a steering data portion from the location specific steering data taking into account the determined location of the antenna; determining an adjusted principal communication direction of the steerable directional antenna taking into account the said selected steering data portion; and adjusting the principal communication direction of the steerable directional antenna in accordance with the said adjusted principal communication direction.