This paper investigates how the location of forced oscillation (FO) source affects the resonance phenomenon between the FO and inter-area oscillations. The analysis is performed in a simple two generator system and the full Nordic power system simulation model. The main finding is that when the FO source is moved from the 'center of the inter-area oscillation mode' towards the 'ends' of the system, the amplification of the FO increases approximately linearly as a function of the voltage angle difference (or electrical distance) from the center. This finding enables an easy evaluation of risks associated with FO sources in different locations. Such information is also valuable generally in transmission system planning and operation.