Demonstration of Charles Kitchin regenerative receiver. 

This one covers 3 to 10Mhz. The front panel controls are Regeneration, Main tuning and "bandspread" or fine tuning from left to right. The 3 controls below that are RF Attenuation, audio tone control and audio volume. This website shows the schematic of it. I am always amazed by how well a simple regenerative circuit can perform. For more information, search on "High performance regenerative receiver by Charles Kitchin N1TEV (amateur radio callsign).