Saturday, 27 September 2025

Tubes 201 - How Vacuum Tubes Really Work, Part 5: The Triode

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Back in 1871, long before the thermionic valve was invented, Maxwell [Max71] published the first study of the effect of a grid of wires on the field between two electrodes. Making some simplifying assumptions, he showed that the electric field as seen at the cathode is equivalent to a plate voltage of:

$V_{eff}=V_{g}+\dfrac{V_{p}}{\mu}$where:  $V_{eff}$ = effective voltage seen at cathode
$V_{g}$ = grid voltage
$V_{p}$ = plate voltage
$\mu$ = amlpification factor

µ is a constant for a given electrode geometry. In other words, the actual plate voltage is divided by µ to get the effective voltage. For example, in a typical medium-µ triode under normal operating conditions, the effective voltage as seen at the cathode is only around 5V, even though the plate is at 100V or more.

Maxwell showed that µ can be calculated as follows. (More and more elaborate formulae for µ were developed throughout the life of the vacuum tube, and Maxwell's is not terribly accurate for real-life tubes).

$\mu =\dfrac{-2\pi d_{gp}}{a \ln\left( 2 \sin \frac {\pi r_{g}}{a} \right))}$where:  $d_{gp}$ = distance from grid to plate
$a$ = distance between grid wires
$r_{g}$ = radius of grid wires

In non-mathematical terms, this means that µ increases directly with the distance from the grid to the plate, and with the ratio of grid wire size to separation, $\frac{r_{g}}{a}$ (also called the grid pitch or shielding ratio). It also means that the value of µ is independent of the distance from the cathode to the grid. The variation of µ with cathode-plate distance is very visible. If you hold up high- and low-µ version of essentially the same tube, e.g. 6SL7 and 6SN7, or 12AX7 and 12AU7, you will see that the plate structure is much fatter in the high-µ tubes.

The assumptions that Maxwell made for his calculations were as follows:

  • the electrodes are infinite, so that the behavior at the edges can be ignored
  • the grid wires are small compared to their separation, i.e. the grid pitch is no more than about $\frac{1}{10}$
  • the distance from the grid to the cathode is at least equal to the grid pitch

When the last condition is true, the effect of the grid wires is seen only collectively at the cathode, with no effect from individual wires even directly under them.

Figure 7: Triode equipotentials

Figure 7 shows the field, by lines of constant potential, under varying grid potentials. It can clearly be seen that when the tube is conducting (i.e.the potential at the cathode is above zero) the field is uniform at the cathode. The effect of the individual wires falls off exponentially with the distance. At half-cutoff, the "bulge" due to the plate's field penetrating the grid is significant up to well over half-way to the cathode. This becomes significant for more modern tubes where the cathode-grid spacing is typically 60% of the grid pitch. Figure 8 shows the field in a cross-section of the tube, at a grid wire and midway between two grid wires, when no current is flowing, i.e. when there is no space charge. It shows that once past the grid, an electron is subject to the full potential gradient due to the plate voltage, but downstream of the grid this is essentially masked by the grid voltage, as predicted by Maxwell.

Figure 8: Section of triode electric field   

Current Flow: the Equivalent Diode

Using the effective plate voltage, we can start to calculate the current that will flow in the tube, following Childs Law, but we also need to know the value to use for the cathode-plate distance. A good approximation is given by:

$d_{eq}=d_{cg}+\dfrac{d_{cg}+d_{gp}}{\mu}$where:  $d_{eq}$ = equivalent plate distance for diode equation
$d_{cg}$ = distance cathode to grid
$d_{gp}$ = distance from grid to plate

(Spangenburg [Spang48] gives a more accurate, and more complicated, formula, but the result is only slightly different). Inserting this into Childs Law gives the complete equation for cathode current under given conditions:

$I_{p}=P\left( V_{g}+\frac{V_{p}}{\mu} \right)^{\frac{3}{2}}$where    $P=\dfrac{2.335\cdot 10^{-6}A}{\left( d_{cg}+\frac{d_{cg}+d_{gp}}{\mu}\right)^{2}}$

$P$ is called the perveance of the tube, and is constant for any given tube geometry. A high-perveance tube is therefore simply one that will carry a high current. It can be seen that there are two ways to increase the perveance, either by increasing the electrode area or by decreasing the electrode spacing. The latter is more effective, but is limited by the mechanical construction techniques and achievable tolerances. Once the closest possible spacing has been reached, the only way left is to increase the area. This is why power tubes are physically large, ultimately leading to tubes like the monster WE212A which stands 13" tall.

Constants (so-called)

A triode is described essentially by three well-known so-called constants:

  • Voltage amplification ($\mu$): as described above, the factor by which the grid reduces the effect of the plate voltage
  • Mutual conductance ($G_{m}$): expressed in milliamps/volt (or nowadays milliSiemens, which means the same thing), the increase in plate current for a change in grid voltage   
  • Plate resistance ($r_{p}$): the effect output resistance of the tube. For small signals, the tube is equivalent to a voltage source in series with a resistance of this value 
In fact, only two of these characteristics are required, since the three are connected by the relation:

$$r_{p}=\frac{\mu}{G_{m}}$$

These constants appear in even the briefest data for a tube. Unfortunately, they are not at all constant. Figure 9 shows (for the 6SN7, a particularly linear triode) how they vary with plate current.

Figure 9: Changes of characteristics "constants" with plate current   

It can be seen that both $G_{m}$ and $r_{p}$ vary a great deal. In fact, this follows from Childs Law. With a little calculus (differentiating the formula with respect to $V_{g}$) and some algebra, we arrive at the formula:

$$G_{m}=\tfrac{3}{2}P^\tfrac{2}{3}A^\tfrac{1}{3}$$

In other words, the value of $G_{m}$ increases with the cube root of the plate current, and hence the value of $r_{p}$ decreases with the cube root of the plate current. Since $G_{m}$ is a key figure of merit for a tube, the manufacturer would always want to show the highest value, whch is to say at the highest rated operating current. More typical and reasonable operating levels reduce $G_{m}$ and increase $r_{p}$. For the 6SN7 shown, $G_{m}$ is 3.2mA/V at 16mA, but drops to 1mA/V when operating at 1.5mA. As in this case, $G_{m}$ typically drops faster than the formula predicts, particularly at low currents and high negative grid voltages.

The curves also show that $\mu$ is not really constant, either. As plate current drops from 5 mA to 1 mA, $\mu$ drops from 20 to 15, i.e. by about 25% - and the 6SN7 is a particularly linear tube in this regard. Newer miniature tubes show a steady drop over the whole operating range.

The explanation for this is not obvious, and the classic tube texts offer no explanation. Mainly it has to do with the changing shape of the electric field in the region between the cathode and the grid as the grid becomes more negative and the current drops. Especially with close electrode spacing (discussed in greater detail below), close to cut off, parts of the cathode below the grid wires are cut off while parts between the grid wires are still conducting - as can be imagined from Figure 7c. The parts which are still conducting have a lower value of $\mu$, which is why they have not yet cut off. (This phenomenon is called inselbildung, German for "island effect").

Another reason, particularly important at low currents, is that the value of $\mu$ is not constant throughout the tube. Variations due to the edges of the electrode structure, grid support wires, and irregular electrode shape mean that there are places where it is higher. As current falls, these areas are the first to cut off, leaving only the lower $\mu$ regions conducting. In consequence, the average value of $\mu$ falls with the reducing current, explaining the distinct tailing off at low currents.

← Previous: Space Charge and Current Flow  Next: Initial Electron Velocity → 

Tubes 201 - How Vacuum Tubes Really Work, Part 4: Space Charge and Current Flow

← Previous: Physical Construction  Next: The Triode → 

If plate voltage is applied to a cold tube, then an electric field is set up between the plate and the cathode. The voltage in this field increases linearly in the distance between the two electrodes. This is shown by the red line in Figure 6. Once the cathode is heated up and starts emitting, the electrons themselves alter the situation, because the electron carries a negative charge. Although this is very small (1.602·10-19 Coulombs), there are a lot of them, and the emitted electrons themselves contribute to the electric field in the space between the electrodes, modifying it from the straight line shown in red in Figure 6. The green line shows the effect using a simple analysis, ignoring initial electron velocity (Child's Law), while the blue line shows the true state of affairs when initial electron velocity is considered.

The term space charge is used to refer to the charge due to the electrons occupying the inter-electrode space. The space charge plays a crucial role in controlling the flow of current, which is at the heart of the controlled amplifying action of the vacuum tube. There are several myths and misunderstandings concerning space charge. It is often implied that it exists only in the immediate region of the cathode, and there are references to the space charge region. It is true that the space charge in this region has particular importance, as we shall see later, but it is present in the whole inter-electrode space. Another source of confusion is the space charge tubes which were developed in the 1950s, for use in car radios. To allow them to operate effectively on the 12V supply in the car, without needing a higher voltage, they used an unusual configuration of grids to limit the reduction in plate current due to the space charge. These are now of interest only to collectors.

Figure 6: Charge distribution between cathode and plate   

The Child-Langmuir Law

The number of electrons depends on the current flow - the higher the current, the greater the number of electrons and therefore the greater the charge. Since the cathode feels the influence of the plate through the negatively-charged electrons between them, the increasing current reduces the attractive force of the plate until the two reach a balance. At this point of balance, the effective field at the surface of the cathode is reduced to zero. Moving away from the cathode, the electrons accelerate. The accelerating electrons spread out, just like cars on a freeway moving away from a traffic jam, reducing the space charge so that the field increases. This is illustrated by the green line in Figure 6, which shows what happens inside a tube when current is flowing under normal operating conditions (under this analysis).

The mathematics of this is beyond the scope of this article, but it is relatively straightforward to obtain the Child-Langmuir law (sometimes referred to simply as Childs law), as it applies to a diode:

$I=\dfrac{2.335\cdot 10^{-6}AV^{\frac{3}{2}}}{d^{2}}$where:  $V$ = plate voltage
$A$ = cathode area (cm2)
$d$ = distance between cathode and plate (cm)

This is the well-known ³⁄₂ power law of the relationship between current and voltage. Note also the bottom of the equation: the current drops with the square of inter-electrode distance. This is why designers need to keep the physical dimensions of the tube as small as possible.

This equation (and the green line in Figure 6) is based on a simplification, that all of the electrons are emitted with zero residual energy. We have already seen that in fact they are emitted with a distribution of energy, and later on we look at the effect this has.

This law strictly applies only to infinite flat electrodes. In reality of course the electrodes are finite, but in a practical tube the effect of this is relatively minor. A similar equation applies to cylindrical electrodes, which still involves the  ³⁄₂ power of voltage, and in fact it can be shown that any electrode configuration will involve this factor.

One implication of this law is that the current flowing depends only on the strength of the field due to the plate in the immediate vicinity of the cathode. This field must be just strong enough to counter exactly the space charge set up by the resulting current. The field elsewhere serves to accelerate the electron flow but plays no role in determining its magnitude.

Saturation

The current emitted by the cathode under normal conditions is far in excess of the current that passes to the plate. The emission of an oxide cathode is upwards of 0.5A/cm2. Even for a power tube, the ratio between the emitted current and the operating current is at least 10. The maximum plate current rating that appears in the specification for a tube is based mainly on considerations of heating, and in pulse operation can safely be exceeded (as it was in TV sweep circuits, for example).

If all of the emitted electrons do pass to the plate, then the operation is completely different. The plate current becomes practically independent of the plate voltage. In a triode, the grid no longer has any control over the current. This mode of operation is called thermal saturation (or just saturation), in contrast to the normal mode which is sometimes called space-charge limited. Under these conditions the full effect of the field due to the plate is felt directly at the cathode, since the space charge (which does still exist) is no longer strong enough to counter it. In fact, the saturated current does increase a little with plate voltage, especially with oxide cathodes, because the increasing field strength can pull more electrons out of the surface of the cathode. This is called the Schottky effect.

It must be stressed though that in audio, no practical vacuum tube circuit operates in saturation, even for short periods. (There are uses in other areas. One is the noise diode, which is deliberately operated with a low heater voltage so that emission is low, and saturation occurs continuously. Another is in high-current pulse switching).

← Previous: Physical Construction  Next: The Triode → 

Tubes 201 - How Vacuum Tubes Really Work, Part 3: Physical Construction

← Previous: Emission  Next: Space Charge and Current Flow → 

There are many different ways that a filament (or cathode), a grid and a plate can be constructed and put together, and many of them have been tried over the years. From here on, we will concentrate mainly on indirectly heated tubes, having a distinct heater and cathode, rather than filamentary tubes. These appeared in the early 1930s, primarily as a way to allow the heater to operate from AC rather than DC.

The only disadvantage of indirect heating is that it is less efficient, i.e. more energy input is required for operation at a given temperature. This is why tungsten and thoriated filament tubes (e.g. 211, 845, SV572) are still directly heated, due to their much higher operating temperature, and also why battery tubes were. For oxide cathodes, the best known filamentary tube in common use today is the 300B, together with a few other power types.

Figure 5: Types of triode construction

There are three common tube structures. Figure 5a shows the cylindrical structure, in which the cathode, the grid and the plate are made as three concentric cylinders. This structure has been little used since the 1930s, presumably because it is more expensive to manufacture. (An exception is rectifier diodes, which are almost invariably built like this). It does however have some theoretical properties that may account for the sonic reputation of the classic model 27 and 76 triodes, which are built this way. The grid is wound as a spiral, generally with two vertical support posts. The grid wire is rigid, and holds its shape once it has been formed into shape.

Figure 5b shows the flat structure used in power tubes such as the 6AS7 and (with a filament rather than a cathode) the 2A3 and 300B. Here the grid is also wound around two vertical supports, but in this case it is flat (although often curved outwards slightly around the cathode). Like the cylindrical structure, this lends itself readily to theoretical analysis.

Figure 5c is a compromise between the two. The grid and the plate are flat, but the cathode is a small cylinder. This is a common construction for small tubes such as the 12A*7 family or the 6SN7. Its behavior is very close to the truly flat structure of Figure 5b. There are many variations on this; for example, the plates are often elliptical rather than rectangular as shown. Similarly, the cathode may be elliptical. Since the characteristics depend directly on the geometry, this results in less consistent operation and is therefore undesirable for audio.

The challenge for the tube designer is to get the grid as close as possible to the cathode. As we will see later, this is the principal factor affecting the mutual conductance of the tube, and for most purposes higher mutual conductance means better. However, there are problems. First of all, the slight variation in grid-cathode spacing inevitable due to manufacturing tolerances leads to indistinct characteristics, since different parts of the tube are behaving differently. Indeed, if the spacing is too close then there is a risk that the two may even come into contact, with disastrous results. Secondly, if the spacing is much less than the distance between the grid wires then the tube performance becomes difficult to predict and may even get worse. This in turn led to pressure to wind the grids from ever-finer wire at an ever-tighter pitch. Miniature tubes typically use grid wire that is less than one-thousandth of an inch thick, with a grid-cathode spacing at its closest of little more than this.

Most of the metal inside a tube is nickel, which has a number of desirable properties. First, it has a high melting point. Copper, for example, would be unsuitable because it would soften and distort. Secondly, it does not absorb a lot of gas onto its surface (the technical term for this is adsorption). Such adsorbed gas is gradually released into the vacuum of the tube, and it is important to minimize it. An exception to the use of nickel is the heater (or filament) which is generally made of tungsten because of the high operating temperature.

The plate is generally blackened, because a black surface radiates heat much more effectively than a lighter one. The only way that heat can be removed is by radiation, and it is this that sets the limit on the power dissipation of a tube. Power tubes have plates that include large radiating surfaces having nothing to do with their electrical function, and even small-signal tubes often have wings or corrugations that serve the same purpose.

Because of the very close clearances, and also because of the impact of tube geometry on electrical characteristics, it is vital to maintain the dimensions to very close tolerances. The metal wires that support the various electrodes are generally held apart by spacers made from mica, which is an excellent heat-resistant insulator that is also very vacuum-friendly and easy to work to precise dimensions.

The heater is inside the cathode. Since the cathode itself is small, there is little room for it and even less room for electrical insulation. A thin layer of alumina (aluminium oxide) is normally used, but at the high temperatures involved this is not a perfect insulator, and if the voltage difference is too high then it can break down altogether. This is why all tubes have a rating for the maximum voltage difference between the heater and the cathode, typically 100-200V. Exceeding this may result in insulation breakdown, and hence failure. Even at lower voltages, there is some resistive and especially capacitative coupling between the heater and the cathode.

It is a very instructive exercise to take a tube to pieces and to measure the internal dimensions. Don't do this with a new Western Electric 300B, but take a defunct octal tube such as 6SN7 (the miniature tubes are too fiddly), break the envelope by wrapping it well in a cloth and tapping it with a hammer. (Be careful doing this, and be careful as well with the shards of broken glass afterwards. Remember that some parts are mildly poisonous, and don't even think about doing it with transmitting tubes which can contain highly toxic beryllium). You can then gradually dismantle the electrode structure, seeing how it is put together. You will find, for example, that many tubes have tiny metal plates welded to the tops of the grid supports, whose job is to get rid of the heat generated on the grid due to grid current. (In this case of the 6AS7G, these are comparable in size to the plates themselves).

← Previous: Emission  Next: Space Charge and Current Flow → 

Tubes 201 - How Vacuum Tubes Really Work, Part 2: Emission

← Previous: Introduction  Next: Physical Construction → 

Underlying all tube operation is the fact that any metal is continuously emitting electrons. Both the number and the speed with which they are emitted increases very strongly with temperature, although emission takes place at anything above absolute zero (-273°C). To understood emission, we have to look at what is going on inside the body of the metal.

In any metal, there are one or two electrons that can easily be detached from an atom, so that inside the solid metal there is a kind of sea of electrons floating around independently of any particular atom. The latter are fixed in place inside the crystal structure and do not move about at all, although they vibrate in place. This sea of electrons is common to all metals, and indeed is really the defining characteristic of a metal and explains many of their familiar properties such as electrical conductivity and the fact that they are shiny.

Since the electrons are not attached to any particular atom, they move about constantly, very much like the molecules in a gas. The average speed of the electrons increases with temperature, but because they are constantly bouncing off of the atoms and each other they do not all have the same speed but rather obey a statistical distribution law.

If an electron happens to be going towards the surface of the metal, then it will naturally tend to fly right out through the surface. However there are powerful forces trying to stop it, for the simple reason that there are positively charged metal atoms inside (because they have lost one or two electrons to the electron sea) and none outside. Thus an electron approaching the surface is slowed down, and only those having enough energy can escape. The amount of energy required is called the work function, and varies for different metals.

This is a convenient point to say how electron energy is measured. First of all, the energy of an electron corresponds directly to its speed. This follows the same law for kinetic energy as anything else, such as a car:

$E=\tfrac{1}{2}mv^{2}$where:  $E$ = energy
$m$ = mass
$V$ = velocity

In this case, $m$ is the mass of an electron, which is about 10-30 kg. Energy is normally measured in Joules, but for electrons this is impracticably huge. Instead we use electron Volts (eV). One eV is the energy that an electron acquires when it is accelerated through a potential field of one Volt. It is about 10-19 Joules, and corresponds to a speed of about 800,000 meters/sec.

The work function of a metal is expressed in eV. For tungsten, it is about 4.5eV. Any electron having less energy than this will not manage to escape, but will be turned around by the electric field close to the surface and will return into the body of the metal.

The electrons escaping from the metal correspond to an electric current, and this current is given by Dushmanns Equation:

$I_{0}=AT^{2}e^{-\frac{11600w}{T}}$where:  $I_{0}$ = emitted current
$A$ = a constant, 120.4 A/cm2
$T$ = temperature in °K (i.e. °C + 273)
$w$ = work function of emitted metal in eV

The striking thing about this equation is the exponential element, which means that emission increases very rapidly with temperature. Figure 3 shows the emission of a tungsten filament as a function of temperature. Even a small percentage change in temperature results in a big change in the emitted current. For an oxide-coated cathode under typical operating conditions, a 10% increase in temperature increases emission by about a factor of 3.

Figure 3: Electron emission as a function of temperature

The electrons that do manage to escape have the same distribution of energy as they did inside the body of the metal. Some of them flop exhaustedly from the surface, while others still have considerable velocity. This becomes important when examining the behavior of the tube. The distribution of energy (and hence speed) obeys the equation:

$p=e^{-\frac{Vq_{\epsilon}}{kT}}$where:  $p$ = proportion of all electrons having energy greater than $V$
$q_{\epsilon}$ = electron charge, 1.602·10-19 Coulomb
$k$ = Boltzmanns constant, 1.38·10-23 Joules/degree
$T$ = temperature in °K (i.e. °C + 273)

It is not a coincidence that the exponential element here closely resembles that in Dushmanns equation. Figure 4 shows this distribution graphically. The great majority of electrons have low energy levels, and the average for an oxide cathode is only about 0.1eV, but there is no upper limit on the energy that a single electron may have. For example, about one electron in a billion is emitted with an energy greater than 1eV.

Figure 4: Electron velocity distribution: proportion of emitted electrons having given energy

Early tubes used solid tungsten filaments. Tungsten has a high work function, and there are other metals which are much more suitable in this respect (for example caesium, whose work function is only 1.6eV). However tungsten has the great advantage of a high melting point - other metals would melt long before they gave adequate emission. A tungsten filament has to be operated at about 2700°C, which is the same as a light bulb. The amount of heat thrown out by any hot object increases with the fourth power of its temperature, which means that a great deal of power (i.e. filament current) is required to replace this lost heat and remain at this temperature.

It was fairly soon discovered that the addition of a small amount of the element thorium (about 1%) to tungsten greatly reduces its work function, to about 2.6eV, allowing filament operation at around 1900°C. This reduces the required power by about a factor of four. Such tubes were called dull emitters, because compared to a tungsten filament (or a light bulb) they were much less bright.

Later it was found that a surface coating of barium oxide (or a mixture of barium and strontium oxides) gave even better results. This is because the oxide is no longer a metal, and the energetic electrons within the body of the filament can escape through the oxide layer at much lower velocity. In fact, the oxide layer is a n-type semiconductor, i.e. one having an excess of electrons, and its behavior is due to this. Oxide filaments have a work function of about 1.1eV, and can be operated at around 700°C. It is this oxide coating which makes filaments and cathodes appear white. There are however disadvantages. The oxide coating is mechanically fragile, and can be damaged as a result of gas in the tube or by vibration or shock. This is why high voltage tubes (such as the 211 and 845) still use thoriated tungsten. It is also relatively volatile, and slowly evaporates from the surface of the filament from where it is deposited in undesirable places such as the grid wires. Emission from an oxide surface is much more complex, in physical terms, than from a pure metal, although it does still essentially follow Dushmanns equation. Overall, though, the advantages of oxide-coated filaments and cathodes for small-signal tubes are overwhelming, and no other materials have been used since the 1930s.

Electrons within the body of the cathode are travelling in all directions, and in consequence so are the ones that are emitted. It turns out that the average lateral (sideways) velocity of the electrons is about the same as their average forward velocity. It is therefore wrong to think of them all travelling along the shortest straight line from the cathode towards the plate.

← Previous: Introduction  Next: Physical Construction → 

Friday, 26 September 2025

Tubes 201 - How Vacuum Tubes Really Work

Copyright © 2025, John Harper

A long time ago I wrote an article on my web page going beyond the basics of vacuum tube (valve) operation, to explain many things which don't seem to make sense if you only look at those basics. It was essentially a summary of the best textbooks and papers from the era when vacuum tubes were high-tech.

The article is still available there, but I've moved it to my blog to make it more accessible and likely to be found.

Note: This is currently a work in progress. There are many broken links and unfinished parts.

Table of Contents

1. Introduction
2. Emission
3. Physical Construction
4. Space Charge and Current Flow
The Triode
Initial Electron Velocity
Noise
Other Things

1. Introduction - the Basics

Everyone knows how a tube works. Current passing through the filament heats it up so that it gives off electrons. These, being negatively charged, are attracted to the positive plate. A grid of wires between the filament (or cathode) and the plate is negative, which repels the electrons and hence controls the current to the plate. For many purposes thats all you really need to know. This article looks beyond the basics, into what makes a tube behave the way it does.

As a start, let's recap the well-known properties of tubes, which will probably be familiar to most people reading this article. We will focus on the use of tubes for audio and will look mainly at triodes, with a look later at multi-grid tubes for audio.

Reassurance for the Math Averse

There are lots of equations in this article. Be assured, if you don't like math, you can skip them. The text tells you the important things that the equations mean. Of course, if you're happy with math, you'll get more from this article. (And there isn't any real math, i.e derivations of things).

The behavior of a triode is fully described by its plate curves, as shown in Figure 1. These show the plate current as a function of plate voltage (on the horizontal axis) and the grid voltage, becoming more negative as we move to the right of the family of curves. The curves for audio tubes generally only show negative grid voltage and positive plate voltage, although it is common to operate transmitting tubes with positive grids, and it is even possible (though rarely useful) to operate with a negative plate. These curves are just a way to represent a three-dimensional surface on the printed page, and in the old days people would even build models from plaster to represent this (e.g. in [Chaff33]). Nowadays we can just ask the computer to draw it for us, as shown in Figure 2. Mathematically, this is a representation of a function which takes two arguments (grid voltage and plate voltage) and gives the plate current as its result. The standard texts (e.g. [Lang53] show how to use these curves to establish the operating conditions for a tube.

Figure 1: Plate Curves for Typical Triode
(ECC82/12AX7)
Figure 2: Surface Representation of
Triode Curves

There are other ways to represent the same function. For example, we can draw the transfer characteristics, which show plate current as a function of grid voltage, with different curves in the family for different plate voltages. It is also possible to draw curves which show derivatives, such as the values of plate resistance and mutual conductance under different conditions. However these are not different characteristics, just different ways of looking at the same data.

One thing that leaps out is that the plate curves are just that - curves. In fact an ideal amplifying device, at least for audio, would show parallel, equally-spaced straight lines rather than curves. Unfortunately no real-world amplifying device can do this, since they all depend on physical phenomena that result in more complex transfer functions. Incidentally the obsession with linearity is somewhat peculiar to the world of audio. In other branches of electronics, such as RF and video, linearity is not so dramatically important since reasonable non-linearity can be filtered out either electronically (e.g. by tuned circuits) or by the receiving device (e.g. the eye). Only the ear can detect such tiny traces of non-linearity.

The plate curves follow quite closely a ³⁄₂ power law, in which the current increases as a function of the ³⁄₂ power of either the grid or the plate voltage. This is especially true at high currents and in the lower (closer to zero) range of grid voltage. While this is not linear, it is closer to linearity than any solid-state amplifying device, which is the main reason why tube amplifiers are nowadays often considered (and certainly by most of you who will be reading this) to be sonically superior. At low currents, especially as the grid becomes more negative, the ³⁄₂ power law no longer applies and the plate curves tuck under very noticeably. The curves are not equally-spaced, even at high currents, but rather get closer together as current increases. All of this is causes extra non-linearity and distortion. This is more true for some tubes than for others, and later on we will look at some of the reasons.

In the sections which follow we take a look at the reality of tube design, construction and operation, which will explain why tubes behave the way they do. On the way we will explode a few popular myths.

Next: Emission → 

Further Reading and References

Of the many books which were written from 1920 into the 1950s about the theory of vacuum tubes, the two which are by a long way the most comprehensive are Spangenburg [Spang48] and Beck [Beck53]. Unfortunately these are extremely difficult to get hold of. These can really be regarded respectively as the US and UK bible on the subject. Spangenburg does however have a number of baffling minor errors in the transcription of formulae from other sources, which means that reference to original sources is required for certainty.

Dow [Dow37] seems to be easier to find, and gives many of the basic principles as well as a good introduction to the use of tubes in circuits. There is also a later book by Spangenburg [Spang57], although shorter than the first and covering semiconductors as well as tubes, which is quite adequate and seems easier to find.

Reich [Reich41] is fairly basic but has the advantage of being available in a reprint [Reich95]. Valley & Wallman [Valley46] deals largely with DC and pulse amplifiers using tubes, and covers several topics such as low-level amplifiers in more detail than elsewhere.

Mitchell [Mitch93] gives the most comprehensive tube data available, unfortunately only for a small selection of tube types. Smullin [Smullin59] gives a comprehensive treatment of all aspects of noise in vacuum tubes.

[Barb97]Barbour E.EL84: The Baby With Bite, Vacuum Tube Valley issue 8, 1997
[Beck53]Beck A.H.W.Thermionic Valves, Cambridge University Press, 1953
[Bench99]Bench S. Directly Heated Triodes operated with lower voltage on the filaments, available at http://members.aol.com/sbench102/dht.html
[Chaff33]Chaffee E.L.Theory of Thermionic Vacuum Tubes, McGraw-Hill, 1933
[Dow37]Dow W.G.Fundamentals of Engineering Electronics, Wiley, 1937
[Frem39]Fremlin J.H.Calculation of Triode Constants, Electrical Communications, July 1939
[Lang23]Langmuir I.The Effect of Space Charge and Initial Velocities on the Potential Distribution and Thermionic Current Between Parallel Plane Electrodes, Physics Review vol. 21 pp419-435, 1923
[Lang53]Langford-Smith F.Radiotron Designers Handbook, Iliffe, 1953
[Max71Maxwell J.C.A Treatise on Electricity and Magnetism, 1871, reprinted by Dover Publications, 1954, ISBN 0-486-60636-8
[Mitch93]Mitchell T.The Audio Designers Tube Register, Media Concepts, 1993, ISBN 0-9628170-1-5
[Reich41]Reich H.J.Principles of Electron Tubes, Wiley, 1941
[Reich95]Reich H.J.Principles of Electron Tubes, reprinted by Audio Amateur Press, 1995, ISBN 1-882580-07-9
[Smullin59]Smullin L.D. & Haus H.A.Noise in Electron Devices, MIT Press, 1959
[Spang48]Spangenburg K.R.Vacuum Tubes, McGraw-Hill, 1948
[Spang57]Spangenburg K.R.Fundamentals of Electron Devices, McGraw-Hill, 1957
[Valley46]Valley G.E. & Wallman H.Vacuum Tube Amplifiers, MIT Press, 1946, reprinted by Boston Technical Publishers Inc., 1964 Revision 2, 2 January 2002.

Saturday, 20 September 2025

Red Rovers and Other Memories of 1960s London Buses


I originally wrote this in 2005, a few days after the last Routemasters were withdrawn from normal bus services in London. London's buses have changed little since then, except in the details of the vehicles used. We now have the "Borismaster" and even a few hydrogen-powered buses, but the average traveller probably doesn't notice.

I grew up on the eastern edge of the area served by London's famous red double-decker buses. Every tourist knows them, even now that the Routemasters have finally disappeared, serving famous sights like the Houses of Parliament and St Paul's. But the area they serve is many times larger than the central London known to tourists, extending into the vast suburban hinterland of Edgware, Romford, Kingston, Croydon and so on.

My home was served by a very unglamorous route, the 174, which connected the largest of the London County Council's housing estates at Harold Hill with its mother town, Romford, and then went on to serve the huge Ford plant at Dagenham. I've been fascinated by travel and transport since I was tiny, and by maps too. In the glory days of London Transport, maps of the red bus system were free. My Dad used to pick one up for me every year when they were published, and I would study them avidly, dreaming of far-off places like Uxbridge and Wimbledon. That sounds funny now, when I've been to so many places (I wrote this sitting on a Boeing 777 flying from California to Japan), but we didn't have much money and our only travel was an occasional visit to my aunt in Brixton, and our annual summer holiday to visit my grandmother on the Essex coast at Dovercourt.

The first bus map I had was in 1959, when I was six. The London trolleybus system was still at its height, the largest trolleybus system in the world by a long way, but the first conversions happened that year and by 1962 the system had gone completely. They didn't reach as far as Romford, although they came close, so I can literally remember every single journey I made on a London trolleybus. The first was when I was maybe four or five We went to the speedway racing at West Ham Stadium, which involved a bus - the 174 - to Romford station, then the electric train to Stratford. At Stratford Broadway, dozens of trolleybuses waited to serve routes that connected the London docks, still the largest and busiest in the world at that time, with the drab working class districts of East London where the dockers lived. There were dozens of routes, each with a bus running every few minutes. There was only one route that went to the stadium, the 699, and it seemed to be one of the less frequent routes. On another occasion we caught the 697, a minor variant which required a spooky walk across a dark, damp park at night.

My next trolleybus ride was a memorial. My Dad, knowing that the trolleybuses were disappearing, wanted to take me on a ride I'd remember - and it worked, because I do. We went up to London on the train one Saturday, and walked from Liverpool Street station to the bus terminus at Moorgate Square. From there we took the 615 to its other terminus at Parliament Hill Fields, on the edge of Hampstead Heath. The return journey was the last London trolleybus I ever took.

I watched the decline of the system through the maps and Ian Allen ABC books, but I was too young to travel on my own to see the end of the system in 1962, in Kingston. Even so I was left with a fascination for these odd vehicles, bus at the bottom, railway at the top - the wiring has points and crossings just like a railway, and the points have to be set correctly or the electric pickups go the opposite way from the bus, which can only end badly.

I've been on trolleybuses in some of the handful of other cities in the world that still use them - Geneva, San Francisco, Boston, and most memorably in Tianjin. I've no idea what Tianjin, in northern China, is like now, but when I went there in 1983 it was a filthy coal-mining town, everything covered in a greasy film of coal dust, most of the large buildings still showing damage from the Tangshan earthquake of 1976. It had - maybe still has - an extensive trolleybus network, which was just like London in its heyday. The Tianjin route 1 connected our hotel to the centre of town, and the buses ran every minute or maybe even more frequently than that. In practice this meant that as soon as one bus left a stop, another arrived.

Long bus rides were very unusual when I was small. To go to London we always took the train, a modern electric commuter train which ran from Romford to Liverpool Street station in the City of London. When we visited my aunt we would catch the 133 from there, over London Bridge and past the Oval cricket ground to her home in Brixton.

Two or three times a year, I would travel with my Dad on route 250 from Romford to another Essex town, Epping, where some elderly relatives lived. This was a long cross-country route, entirely on country lanes and through quaint English villages, passing on its way the aerodrome at Stapleford Abbots where I would sometimes be lucky enough to see a small plane rising from the grass runway. At first the 250 was operated by a very old-fashioned kind of bus, the TD class, a single decker with the engine beside the driver just like the double deckers. Later these were replaced by London's modern RF class, the standard single decker of the 1950s, with the entrance beside the driver and the engine tucked tidily away under the floor.

The London bus maps were printed on thin paper - they weren't meant to last very long. My first map from 1959 fell apart quite quickly - in recent years I've been very lucky to get another, in perfect condition, but I missed it for years, since it was the last record of the full trolleybus system.

One feature of London Transport at that time was the Red Rover ticket. This cost three shillings (£0.15) for a child, and allowed unlimited travel anywhere on the red bus system for a whole day. This was just within my weekly pocket money, and for months I dreamed of buying one and travelling to all these exotic places I had so far only seen on the map. And then, one day, I declared my intention of doing so. I must have been eleven or twelve. I have no idea what my mother thought of the idea. Today it would be unthinkable to let a child loose like that, but those were more innocent times. 


So, one Saturday morning I left home, my duffel bag over my shoulder containing my picnic lunch. I stopped at the tiny travel agent's shop to buy the precious ticket, a piece of red card about 1½ inches by 3, stamped with the day's date to validate it, and from there round to the familiar bus stop to catch a 174 into Romford. My target was the Woolwich Free Ferry, another London institution which fascinated me. It ran - and still does run - from Woolwich on the south bank of the Thames across to North Woolwich on the north bank, and as the name suggests, it's free, for both pedestrians and cars.

I don't remember the exact details of that first journey. I think I went to Becontree Heath - if not that time, then certainly at other times. This was a rather improbable bus station in the middle of nowhere, where several routes terminated and others passed through. Eventually I arrived at Canning Town, in the heart of the dock area, for the last leg of my journey to North Woolwich, and a new experience. The standard London double-decker bus at that time was called the RT. Nearly seven thousand of them were built in the early 1950s, to a design that in most respects went back to the late 1930s. They were very sophisticated for their time. The RT was a wonderful bus. Although the last one was withdrawn from service in London in 1978, there are still hundreds of them privately preserved and showing up at bus rallies all over England throughout the summer.

But my choice of Canning Town was made to see something very new, the Routemaster. These had been introduced in 1959 and at this time they were still only in service on the former trolleybus routes, which they had replaced. Since Romford had no trolleybuses, the Routemasters were for me a very exotic species, occasionally glimpsed in central London on journeys to see my aunt, but never experienced.

From Canning Town to North Woolwich ran route 69, replacing the trolleybus route 669. And so a few minutes after arriving in Canning Town - a damp, dismal place of run-down small houses and small shops - I was on my very first Routemaster. What a splendid vehicle it was! It seemed gleaming new - although I suppose it must have been a few years old - and had amazing innovations like a heater for the passengers. (All earlier London buses, despite their famous open platform, had no heating at all, except for the driver). What I remember most though, even now, is the unique noise they made. The engine - the AEC AV590 - made a very distinctive sort of hammering noise as it accelerated, unlike any other diesel engine ever made.

The RM - the designator used in the fleet number painted in gold on the engine of every bus - was the first London bus to have a fully automatic gearbox. The driver could select a gear manually, but if he (and I do mean "he" - there were no women bus drivers in those days) left it in top gear, the gearbox would shift automatically. However it wasn't very good at it. As the bus pulled away from a stop, the engine would accelerate normally, then at some point the noise would change to a sort of strangulated sound, the bus would slow a little, and then with a tremendous "thunk" the higher gear would engage and the bus would lurch forward with a terrific jolt. While the RM was a fantastic bus, providing public service to Londoners for an incredible 46 years, the gearbox was not one of its better bits. I've since read that it took years to get it right.

After a short ride through unlovely places like Silvertown, we arrived at the ferry. This part of London is now completely unrecognisable. The docks gradually fell into disuse in the 1960s and 1970s. When I was very small and we used to visit my aunt, the docks extended right the way up to London Bridge. The "Pool of London", the stretch of water between Tower Bridge and London Bridge, still had working cranes on the southern side. I'd stand on London Bridge with my Mum, watching the boats loading and unloading.

By the 1980s the London Docks were a wasteland, a mixture of Victorian brick terraces and thoroughly nasty modern tower blocks and prefabricated housing from the 1960s, with high unemployment and no hope for the future. Then the government had the inspiration of creating a whole new city there, and now "Docklands" is a metaphor of urban reconstruction. The huge warehouses have now been converted to apartments, massive new offices stand where there were ships half a century ago, and the long, straight waters of the King George V dock now hold the runway for London City Airport. But in 1964 the docks were still active, the cranes still doing what they were built for and not lined up as giant ornaments alongside modern apartments.

North Woolwich is a disappointing, bleak, windswept place, a mile or so from the docks, with only the ferry terminal and a small, old-fashioned station, terminus of the former Great Eastern branch line from Stratford. It's just a short walk from the bus down the gangplank to the waiting ferry. It isn't exactly Life on the Ocean Wave but to an urban lad it still seemed an exciting place, with its smell of seaweed and damp creosote, and boats hooting eerily as they passed up and down the river.

On my first visit to North Woolwich I just crossed over and came straight back. I didn't have time to explore the mysterious lands south of the river, not this time, although I did later. Then I took a 69 back to Stratford, sitting in my favourite seat at the front downstairs, looking out of the window behind the engine. My other favourite seat was upstairs at the front, but in those days the upstairs was for smokers and often the air up there was almost unbreatheable. I realised I was going to be very late home. I'd promised to back by 6, but a look at my trusty Timex wind-up watch showed me that it was 6 already, and I still had a long way to go. There was nothing to be done - it was still a few decades before every child would have his own cellphone. At Stratford I caught an 86 which went directly, if slowly, to Romford.

The 86 was a curious route. It set out from Hornchurch, the other side of Romford, then continued along the London Road which, as its name suggests, leads directly to London. It got nearly all the way, to Stratford, and then lost heart. Instead of continuing to London it dived down a side-street and terminated ignominiously at Limehouse. This has an exotic, tropical sound to it, but I went there just once on one my trips and it was a very unlovely place, like many of London's bus termini remote from any obvious source of traffic, alongside a railway line but not at a station.

If you did want to catch a bus to London, there was always the Green Line route 721 to Aldgate - though not if you were travelling on a Red Rover. Green Line buses ran from all around the Home Counties into central London, mostly then continuing across London to another outer suburban destination - Gravesend to Windsor, or Luton to Reigate being typical journeys. Our 721 was unusual in running only to Aldgate on the eastern edge of the City. But I never, ever caught a 721, or any other Green Line service - the train was much quicker and I never saw the point. I guess others must have felt the same way, because the whole system disappeared quietly some time in the 1980s. 

There were other bus operators in Romford. Just one green London Transport route made it there, the 370 which ran across country to Tilbury. Eastern National, whose buses I knew well from holidays at Dovercourt, had several routes - for example the 251, which ran from an obscure north London terminus (Wood Green), across the suburbs to Romford, and then by a leisurely route through many small towns to Southend. 

A much smaller operator in the area called themselves Super Coaches, and operated a small fleet of retired London Transport buses from a muddy, swamp-like yard in Hornchurch which I visited a few times in my teens.

I finally got home from my first Red Rover outing maybe two hours after I was supposed to. I don't remember that anything very bad happened - I didn't find my poor mother in tears, or get yelled at, so I suppose they must have been expecting it. And they certainly didn't stop me doing it again.

Other trips took me to different places. A couple of times I took the Woolwich Ferry then walked into Woolwich to travel south of the River, taking route 51A to the oddly-named Green Street Green. Unlike many London place names, which sound a lot more bucolic than they actually are, this really was quite a nice place. There was a big green where I could eat my picnic lunch, and a 1930s style pub, on the very edge of built-up London. From there I took buses across the southern fringe of the red bus area to places like Bromley, which I've never had any reason to return to since.

I never even gave a thought to timetables. For the most part the red bus routes were so frequent that you could just show up. The trolleybus routes, with a bus every minute, were exceptionally frequent, but on most routes you wouldn't wait more than ten minutes or so. I can only remember being disappointed a couple of times by having to wait a long time. Once I wanted to catch the elusive route 100. You might think that this number would be reserved for something special, and it was - but in the wrong way. It was a special workers' service for the giant gasworks at Beckton, on the river near Barking, and one of only two routes marked on the map as "irregular". (The other also ran from Barking, the 23C to the power station at Creekmouth). I waited for a while but with no posted timetable it was hopeless.

On a couple of exceptional occasions, I scraped together the money to buy a Twin Rover. This cost five shillings - nearly twice as much - and allowed unlimited travel on the Underground system as well as the buses. Once I went to Edgware, the north-western extremity of the system, and another time to Uxbridge, on the Metropolitan Line. These trips let me explore routes I would otherwise never have got to - a bus travels very slowly through London's urban sprawl. But there were fabled routes I never got to travel, the 84 north to leafy St Albans (and incidentally the longest route in the system), the 65 south to Chessington. I never took any interest in the actual places that I visited, which I suppose is a very anorak-y way to travel. I can confess, at this distance in time, that not only did I tick off the numbers of the buses I'd seen in my little Ian Allen fleet book, I even at one time kept a notebook for all the destination blinds I'd seen.

London's destination blinds were something special. Long before modern electronic displays, a blind was a handcrafted work of art made from linen and paper. It was a roll about three feet wide and, rolled up, about four inches across - unrolled they were ten or twelve feet long, consisting of a series of panels each about four inches high with a destination on them. Most buses in the world simply  say which town they were going to, or in towns they would have the name of a district or a street: "Docks", "Gasworks Avenue". London was quite unique in having a little qualifying name at the right in smaller type, small enough to allow two lines, often the name of a street or a pub. So the 174 would go, not to "Harold Hill" or "Noak Hill" (its two destinations in our direction) but to "Harold Hill (Gooshays Drive)" or "Noak Hill (Tees Drive)". Destinations without some qualifier did exist, but were less common (for example, "Romford Station", not "Romford (Station)").

Even when buses went absolutely nowhere else in a small village, this would often appear. Thus route 247 had the challenging, space-wise, destination of "Brentwood (Robin Hood & Little John)". The interest of these blinds was the large number of destinations they carried that were hardly ever used. So if you watched carefully, nearly all buses on a particular route would be going to just a handful of destinations, but every now and then you'd see one going to a place you'd never seen before. Typically, these were mid-route turns used when the inspectors, important-looking chaps in dark blue raincoats and peaked caps who stood around major bus stops, decided to turn some buses back short to try and get things back to schedule. It was at times like this that you would see "Harold Hill (Myrtle Road)". Sadly, my notebooks have long since disappeared. I did once buy a used blind, from Hornchurch garage, but I think that has been lost in a series of international house moves too.

Today the London bus system has changed beyond measure. The buses are still red, after a brief, awful period in the 90s when they showed up in all kinds of strange colours, and most of them are still double-deckers, the ill-adapted "bendy buses" notwithstanding. The last Routemasters were withdrawn from regular routes three days before I wrote this piece. I find it sad, but not surprising considering their age - maintenance must have been a nightmare, given that the manufacturer (AEC, created by London Transport to build its buses just before World War I) went out of business in the early 70s. They lasted 46 years in regular service, or 51 years if you count from when the first prototypes appeared.

To put that in perspective, if previous generations had lived as long, the first Routemasters would have been replacing B-type buses, famous as "Ole Bill" from World War I, with open upper decks and staircases, no protection for the driver, and solid tyres. The Red Rover ticket no longer exists as such, but there are various all-day tickets available if today's twelve-year olds wanted to repeat my adventures from the early 60s. But in today's climate I don't think Britain's nanny society would look favourably upon a parent who allowed it.


My Grandmother, Carrie Harper, 1891-1972


When I knew my grandmother she lived in the fading holiday town of Dovercourt, Essex. Until I was 9, we spent our summer holidays crammed into her tiny house there. It was a week of outings to the beach on the exotic (to me) green Eastern National bus, building sandcastles, and a choc-ice if I was lucky.

Carrie, left, and her sister Dora, centre
To me she was just "Granny" - as a child I never even knew she had a real name. To my seven-year old eyes, she was not just old but positively ancient. It was only after her death, when my parents found the old pictures that I've been able to reproduce here, that I discovered that she was once young and beautiful. The picture above shows her when she was about 18.

A few years ago my mother, now also departed, wrote some notes about Carie and her life, which I've reproduced below. When she mentions "her son", that is my father, and my mother's husband, Reg.

My Mother's Recollections

Caroline Harper - always known as Carrie - was my mother-in-law. She was born in 1891 and she then lived at Mill Farm, Great Bromley with her mother and father, George and Elizabeth. The nearest town was Colchester, Essex.

It is obvious that Carrie was quite a lively young lady. The first story about her was that, one evening, she missed the last bus back from Colchester and had to walk home in her high heeled shoes, and apparently her feet were in a bad way, so her father took her shoes and chopped the heels off with an axe.

Arthur Bines
Meanwhile, she had a steady boyfriend, Arthur Bines, who lived a few miles away, probably in North Essex, as can be seen on the postcard he sent her in 1908 (below), and it seems they met regularly. He was the father when she became pregnant in 1911 and in those days this brought shame on her whole family. Her son was born in Tendring on Christmas Eve and she named him Arthur Reginald. With no alternative, she had to have him adopted, and he spent the next ten or eleven years in Epping with his foster-mother. Carrie and her younger sister, Dorothy, went to work in London and looking at their photos, they appeared to be leading a very happy life.

Arthur entered the army for the 1914/1918 war and, after he was discharged, went to the USA, presumably to "make his fortune". It must have worked to a certain extent, because he did send the money to enable her and Reg to join him in USA but, meanwhile she had met, fallen in love with and married Ferdinand Segers, who had been in the Belgian army. He must have got papers somehow, because he was a senior chef at the Savoy Hotel in London, so the money Arthur had sent was spent on setting up a lodging house at 60 Neal Street in the west-end of London (which is now a very fashionable shopping and eating street near the Covent Garden complex). The lodging house had 12 lettable rooms and they were all taken up by staff from abroad who worked at the Savoy. Carrie ended up decorating, cleaning, washing bed linen, and so on, for the grand sum of £1 per week for each inhabitant, and she was living in the basement. 

Ferdinand, her Belgian Husband
(though not for long)
Then, after a few years, Ferdinand left her to live with another woman. Her son Reg was, by this time, 13 years old, so she brought him to live with her in Neal Street. As soon as he was 14 years old - school-leaving age in those days - she got him a job at the Savoy, training as and shortly becoming a junior waiter, so this increased her income. He lived with her and worked in other restaurants until he got married for the first time in 1936. He stayed in Neal Street for so long because he was a very keen autograph collector and it was handy for the west-end theatres. Carrie later also worked in the evenings in a restaurant in Charing Cross Road, as she was saving for her retirement. She planned to live near her brothers, Frank and Dick and their wives, where they were living in Dovercourt, a seaside town in Essex.

She found a two-bedroom bungalow for sale in Dovercourt for £400, which she bought, but couldn't move there until she had a bit more money, and because she wouldn't get the state pension for a few years. So when Frank asked her if meanwhile his son and family could rent it from her, she agreed; but then, when she was financially able to move there, her nephew and family had trouble finding an alternative home. Eventually she moved to her new home in Dovercourt but, by then Dick had moved some distance away and Frank had bought or rented a smallholding a few miles away.

As regards making friends, there was a problem for her, although I don't think she realised. She had become so used to conversing with the foreign lodgers that her speech and grammar sounded as if she were not English and Dovercourt was very English. The first thing she did was redecorate the whole bungalow to her liking and make any repairs that she considered necessary, and her favourite tool was a hammer. She thoroughly enjoyed working and gardening in her own place.

Gradually she became friends with some other women and, after a few years, Frank and his wife moved back to Dovercourt and she settled down. She even joined the Hard of Hearing Club and, when she went there, she wore her hearing aid. That was the only time she wore it. When she was visited by her son and family, she liked to walk with her grandchildren. Her favourite was a nearby graveyard, but the children seemed to enjoy it too. When her son and family were staying with her, they had to answer to the name of Segers, because she didn't want anyone there to know that Reg was illegitimate.

As she got older and not able to do as much work in the house or garden, her son visited her regularly to help; and once a year the whole family went there for a week to do any big jobs which were needed - one such instance was when they had to lift all of the living room floorboards, where they found that the wooden beams underneath it had rotted away as they stood directly on to the earth and had to be replaced as additionally they were smothered in red ants. It was a very busy week when not much was seen of the beach.

Having not heard a word from Ferdinand since he left her, she received a letter from him (how did he know her address?) telling her that his partner had died and he was living alone in Bristol and was very lonely. He asked her if she would visit him and, of course, being the type of woman she was, she agreed. When she arrived there, she found that he was almost an invalid. She cooked him a meal and, later in the evening he asked her to open a drawer and pass him some papers. When he received them, he sorted out and destroyed some papers and told her afterwards that it was his will and, as they were still legally married, she should have all of his possessions.

What she didn't know at the time was that when he left her, the woman who became his partner, already had a very young daughter who believed that Ferdinand and her mother were married and she was their daughter. After Carrie had been with him a few days, he was taken ill and, when he was hospitalized, they diagnosed his illness as food poisoning and he died soon after. Carrie was so worried that she sent her son a telegram - she was afraid she would be arrested, because, some years previously, while still living in London, she had been admitted to hospital suffering from food poisoning. It took two months to bring her back to health, so she had a lot of knowledge about this illness. Eventually, when a post-mortem was carried out on Ferdinand, it was found that a diseased liver was the cause of his death.

When she was at his flat after his death, she was visited by his now adult daughter who found it hard to believe that Carrie was his legal wife and she was not even Ferdinand's daughter. Needless to say, she was very upset. His possessions were found to be almost worthless except for a French chiming clock. So, after arranging his funeral, Carrie returned to Dovercourt, with the clock. 

One evening in 1972 while she was working alone in the bungalow she collapsed on to the floor and became unconscious; unfortunately, she was not found until the following morning, when she was ambulanced to hospital but, by then, she was suffering from pneumonia. Her son was advised and travelled down to see her for what proved to be the last time, and sadly she died the following day. When her son visited the bungalow, he found the hammer on the floor where she had been working before she collapsed. 

My Own Recollections

Granny had a dog, Tony, which had been a cause of mild upset in the family - my parents wanted to call me Tony, but felt they couldn't once she had adopted the spaniel mongrel shortly before I was born.

Carrie at 80, as I knew her, with her dog Tony
I remember her very odd accent, a mixture of rural Essex and Belgian. She spoke of a "brasserie" when she meant "brassiere" - the result no doubt of too long spent with foreign waiters. Although she only wore one, like her hearing aid, when she went to the weekly Hard of Hearing Club meeting.

A few times we visited Mill Farm, her birthplace, to see my Uncle Ernest - her brother-in-law, from Switzerland and actually called Ernst, who had married her sister Dora before her untimely death from the scourge of the times, tuberculosis. It was quite an expedition - although it was less than twenty miles, the bus ran just a couple of times a day, winding its way along twisty roads, and took forever to get there.

She was always active, pottering around the house or the garden. It seems to me that there was always a smell of wet paint somewhere. She had a shed, mysteriously full of stuff, including an ancient hand-operated wooden mangle. I took her strength for granted. To choose to remain an unwed mother, in 1911, must have taken a phenomenal strength of character.

Her funeral, in 1972 remains clearly in my mind. My maternal grandparents died when I was a small child. Carrie, or Granny, was the only one I have any grown-up memories of. The funeral was in Colchester, a long journey from where I was living in the north of England at the time. There was a school next to the chapel, and children were playing as we filed out. It seemed fitting, a final lively and youthful tribute to my grandmother.

Postcard from Arthur Barnes (centre), 1908

Mill Farm, probably in the 1890s. The gent
to the right looks remarkably like my
father, and is no doubt a relation