Tropadyne
The Tropadyne principle describes a circuit variant of the superheterodyne method for radio reception .
In the early days of radio broadcasting and in the early days of radio technology (i.e. between 1923 and around 1930), several circuit principles and design variants were given names in -dyne.
In the Tropadyne principle, mixing takes place in an electron tube as a so-called self-oscillating mixer. The grid bias of this tube is generated analogously to the Audion by rectifying the oscillator frequency at the grid current start point. To reduce the interference radiation, the antenna input is coupled to the oscillator circuit via a bridge circuit.
Goal of the Tropadyne Principle
The Tropadyne principle corresponds to the goal of building a superimposed receiver (superheterodyne receiver, or super for short) with as few tubes as possible. It was in competition with the feedback audio.
With feedback audio, two tubes are sufficient for the necessary amplification . In a number of receivers with triodes , however, the gain was increased by a factor of four using a coupling transformer.
The feedback audion is associated with the risk that interference radiation is emitted due to (conscious) incorrect operation (so-called whistling). The feedback operated shortly before the start of the oscillation also leads to a selectivity that can be compared with that of superimposition receivers. The additional oscillating circuits present in so-called multi-circuit receivers do not serve so much for selectivity, but for cross-modulation resistance . In the heterodyne receiver, all intermediate frequency oscillating circuits (filters) contribute to the selectivity to an approximately equal extent. The selectivity of the audion with feedback is therefore only achieved with a superposition receiver (super) with a higher expenditure of tubes (with the then common concept with one amplifier stage per filter).
The principle of audion with feedback determined the manufacture of the people's receivers or single-circuit receivers . The superimposition receiver became generally accepted as “super” (home super, suitcase super, large super super) with the rationalization of tube production. But there was no longer any interest in the Tropadyne principle.
A specialist dictionary from 1957 no longer mentions the term tropadyne.