Electronic Devices With Antenna Mounting Structures

A head-mounted device may be worn on a head of a user. While the head-mounted device is being worn, optical modules in the head-mounted device may provide images to eye boxes located rearward of the head-mounted device. A forward-facing display on a front portion of the head-mounted device may be covered with a transparent housing portion forming a display cover layer. An antenna may be mounted in the device. An antenna support member may be coupled to the head-mounted housing. A biasing member such as a layer of foam may have first and second opposing surfaces characterized by surface normals. The foam may be characterized by an axis of preferential compression that is not parallel to the surface normals. The support member may press against the foam so that the antenna presses against an edge portion of the display cover layer or other overlapping dielectric layer.