This is a one valve [tube] radio that believe it or not I constructed 48 years ago. It remained lost but was discovered again during a recent house move. The valve used is a battery R.F. pentode dating from around 1948 on a B7G base. The type number is DF91 or the American equivalent, the 1T4. This valve was used extensively in radio equipment during the second world war and was widely available for a few pence on the government surplus market. The receiver is a simple detector with reaction [feedback]. In simple terms reaction brings the valve into a high state of efficiency improving selectivity [being able to seperate stations] and sensitivity [able to pick up very weak signals]. This simple circuit dates from the 1920's and can be used with any type of radio valve with slight modification. The filament supply [1.5v] is supplied from a single cell and the H.T. supply for the anode from three 9v batteries in series. Surprisingly the circuit will operate with an anode [plate] voltage as low as 18v and weak signals can be heard as low as 9v! The volume in the high impedance telephones is very good but I have connected to an old valve amplifier to demonstrate its capabilities. Thanks for watching.