We did the receiving valve numbering system sometime ago in this blog and I thought it was about time we explained the corresponding transmitter valve system, so here we go:-

FIRST LETTER - this describes the general class of valve

M    LF power amplifier or modulator triode

P    RF power pentode

Q    RF power tetrode

R    Rectifier

T    RF power triode

SECOND LETTER - this describes the type of cathode

G    oxide coated mercury rectifier filament

V    oxide coated indirectly heated cathode

X    tungsten uncoated directly heated filament

Y    thoriated tungsten directly heated filament 

Z    oxide coated directly heated filament

THIRD LETTER - this describes the envelope material

S    silica envelope

FIRST NUMBER - this denotes the anode voltage Va in kV

05   0.5kV (500V)

1     1.0kV (1000V)

5     5.0kV (5000V)

12   12.0kV (12000V)

SECOND NUMBER - this denotes the valve output

For valves of </= 5kV the figure denotes the maximum anode dissipation in watts (W)

For valves of > 5kV the figure denotes the maximum anode dissipation in kilowatts (kW)

For rectifiers, the figure denotes the maximum rectified current per valve in milli-amperes (mA)

SECOND NUMBER SUFFIX - denotes cooling type

A     forced air cooling

W    water cooled

Here are some worked examples using the above convention: -

A QV04-7 is an RF power tetrode with indirectly heated oxide coated cathode with the anode rated at 400V with a 7W dissipation.

A TX12-20W is an RF powee triode, water cooled with tungsten filament with the anode rated at 12kV with a 20kW dissipation.

An RG3-250 is a mercury vapour rectifier having a 3kV anode voltage and a rectified output of 250mA.