The TRF, Tuned Radio Frequency receiver was still the leader, but many superhet receivers were being made. This is the schematic for the Atwater Kent shown on the 1920's page. Interest in Short Wave listening grows.
Switches begin to replace plug in coils for changing bands.
The first 'midget' sets are sold. 1932 AVC , or Automatic Volume Control was introduced. The first auto radios are sold. They are battery powered, and I would place the tombstone model in the mid 30's, and the table radio in the 40's. All-Wave' receivers are a hit this year, bringing in radio from foreign broadcasters.