Axial flux electrical machines (AFEM) with shaped disk structure increases the power-to-weight ratio using HTS materials. The introduction of permanent magnets on rotor disk and of superconducting coils on stator disk, instead of conventional field and armature winding, respectively, allows the development of lighter, more compact, and more performing AFEM. In this paper, we report the electromagnetic properties of an HTS coil in a double pancake configuration measured at LN2 temperature. Also, simulation studies by means of finite element and constant lumped models are reported. Commercial grade ReBa2Cu3O7-x (Re=Y or rare earths, ReBCO) tape and epoxy resin have been used for coil winding. The combination of experimental and simulation results allow ac losses, in the HTS coils used in an all-superconducting machine design, to be estimated.