[turretslug]

There's an appealing simplicity to that circuit- aside from the double-anode heptode itself. "Bring me colour with minimum bottle count, let the tube itself do the colour-difference matrixing". (I'm using "tube" in the British, rather than American sense!)

Whilst FM stereo radio and TV colour transmissions brought balanced demodulation into widespread consumer use and probably inspired several double-anode propositions, I wonder when balanced mixing really took off in radio usage? VLF superhet applications must have emphasised the need to keep the LO from deafening the IF strip to designers, and Racal's VLF adaptors are nice examples of balanced mixing but used mainstream conventional devices rather than newer "exotica" like the 7360.