Western electric 244 a brochure

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BELL SYSTEM PRACTICES SECTION AB46.235
Transmission Engineering and Data Issue 1, September 1936
Vacuum Tube Data A T & T Co Standard

Wafer/7 Electric
244A Vacuum Tube

Mr7 M x .
» 5

F.

Classlfloation-Low-power trlode with Indirectly heated cathode

For most applications. the heater element of the 244A tube may be operated on alternating
current.

Applications
Audio-frequency voltage amplifier.
Audio-frequency power amplifier where small amounts of power are required.
Oscillator.

Dimensions-Dimensions, outline diagrams of the tube and base, and the arrangement of the
electrode connections to the base terminals are shown in Figures 1 and 2t

Base-Medium, five-pin type with bayonet pin.
SockeV-Standard, five-contact type, such as the Western Electric 141A socket.
Mounting Positions-The 244A tuhe may be mounted in any position.

Average Direct Interelectrode Capacitances

A B
Grid to plate, put ............... . . . . .......... 3.3 3.2
Grid to heater and cathode, ant. .......... i . . . 3.1 3.3
Plate to heater and cathode, uni-n . . . . . . .......... 2.8 3.2

Column A-Based tube without socket.

Column B-Tube alone when measured in 141A socket mounted in metal plate; mounting
plate connected to heater and cathode.

Copyright 1936 Western Electric Company. Incorporated

244 A

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244.5

Heater Rating

Heater voltage ...................... 2.0 volts, a.c. or d.c.
Nominal heater current. ............ 1.6 amperes

The heater element of this tube is designed to operate on a voltage basis and should be operated
at as near the rated voltage as is practicable.

Cathode Connection-When the heater is operated on alternating current, a reduction of
hum in the tube may usually be obtained by connecting the cathode to a center tap on the secondary
of the heater transformer or to the center point of a suitable resistance connected across the heater
terminals. If voltage must be applied between the heater and cathode, it should be kept as low as
possible and should not exceed 90 volts.

Characteristics-Plate current characteristics of a typical 244A tube are shown in Figure 3 as
functions of grid bias for several values of plate voltage. Corresponding amplification factor, plate
resistance, and transconductance characteristics are given in Figures 4, 5, and 6, respectively.
Plate current characteristics are shown as functions of plate voltage for several values of grid bias
in Figure 7.

Operating Conditions and Output-Permissible operating plate and grid voltages are
included within the area, ABCD, in Figure 3. Amplification factor, plate resistance, transconduc-
tance, and performance data are given in the table on page 3 for a number of typical operating condi-
tions represented by selected points within this area. The less severe operating conditions should be
selected in preference to maximum operating conditions wherever possible. The life of the tube at
maximum conditions may be shorter than at less severe conditions.

The performance data include the fundamental power output in milliwatts and the second and
third harmonic levels in decibels below the fundamental for values of the load resistance, R, equal
to one, two, three, or five times the plate resistance, r,,. The peak value of the sinusoidal input,
Em, which gives the indicated power output, Pm, and harmonic levels, F2, and Fm, in each case,
is numerically equal to the grid bias. For a smaller input, Eg, the output and harmonic levels,
except for very low third harmonic levels, are given approximately by the following relations:

EE 2
P P'(E...)

F2

E
F2... + 201 -
Ogle E:

E
E; = F3,n + 40 loglo Elm
E

The level of the third harmonic in the 244A tube is usually low and may difler widely in individual
tubes. The values given in the table are for a typical tube,

NIicrophOnic and Sputtel Noise-With a plate voltage of 135 volts, a grid bias of -6 volts,
and a load resistance of 100,000 ohms, the mean microphonic noise output level of the 244A tube,
measured in a laboratory reference test set, is 32 decibels below 1 volt. The range of levels of indi-
vidual tubes extends from 24 to 43 decibels below 1 volt. Since microphonic noise depends on the
type and intensity of the mechanical disturbance which produces it, the values given here are useful
chiefly for comparison with the levels of other tubes which have been tested in the same way.

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