Sensibly equivalent¶ to:
The QQV03-20 is a transmitting double beam tetrode for VHF and UHF applications, we have not found the data-sheet for this original version. An improved version the QQV03-20A soon became very popular as both a Class C amplifier and Class B modulator. This first version has raised seals for the anodes. The QQV03-20A has a hard glass top and does not have the raised seals. Versions made under the CV specification had gold plated pins.
This excellent example of good design from 1952 was later re-worked by Mullard into the taller QQV06-40A, for a small additional height twice the output power was possible.
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 use the designer would take care to keep the grid circuitry below the chassis with the anodes being connected to circuits remote from the input. This way undesirable feedback could be avoided.
The European design of internal capacitors for neutralisation can be seen at the top of the valve. Such neutralisation prevented parasitic oscillations during operation in a well designed layout.
In addition to use as transmitter power amplifiers the upper frequency of 600 MHz made them popular for frequency multiplication.
The reverse showing the central section with beam plates, screen grid, cathode and two control grids.
These images courtesy of the late Andy Cowley.
The wide glass tube envelope is 43 mm in diameter and, excluding the B7A base pins, is 53 mm tall.
References: Data-sheet. Type QQV03-20 was first introduced in 1952.
Absolute Maximum Operating Conditions¶
Updated August 13, 2019.