Amplifex frame aerial. Early frame aerial for home wireless set made by Amplifex, United States.

A frame or loop aerial uses wire wrapped multiple times round a support structure. The aerial was convenient for confined spaces where there was less opportunity to run a long wire aerial.

The aerial arrangement had advantages in directivity and selectivity. Directivity measures the degree of radiation in a single direction and allows the aerial to distinguish the signal from interfering stations. Selectivity improves fine tuning to the required frequency and to reject others, creating a clearer sound.