The QQV03-20A from Mullard is a double beam tetrode transmitting valve introduced in the early 1950s.
Following the European pattern, a central flat cathode is surrounded by a split control grid (one half per valve), a common screen grid is wound next. The two beam forming plates can be seen either side of the central assembly. The anodes are finned for good heat dissipation and clearly separated from the central structures, the anodes are brought out to pin like top caps.
The heater runs at 6.3 Volts when both halves are in parallel or 12.6 Volts when in series. For 6.3 volts pins 1 & 7 are connected together with pin 5 as the other end. For 12.6 Volt operation the voltage is connected to pins 1 & 7 with pin 5 left unconnected.
In addition to use as transmitter power amplifiers the upper frequency of 600 MHz made them popular for frequency multiplication.
This valve is also marked as a CV2799 indicating a direct equivalence.
Each anode has a flat surface facing the grids and a sloping wing either side that bends away from the central assembly of beam plates, common screen grid, cathode and control grids.
The beam plate with screen grid winding visible in the centre.
