Western electric 101 fa brochure

Page 1

BELL SYSTEM PRACTICES , SECTION AB46.025
Transmission Engineering and Data Issue 1, November 1939
Vacuum Tube Data A T & 1 Co Standard

Waiter/1 Electric
101FA Vacuum Tube

a

unsm / ,7

Classification-Low-power, filamentary trlode

This tube is similar to the 101? (dome) tube except for modifications in the characteristics
to obtain higher gainl

Applications-Voice-frequency repeaters and other telephone equipment requiring higher gain
than can be obtained from the 101F tube.

Dimensions and Connections-The outline diagrams of the tube and base, giving the di-
mensions and the arrangement of the electrode connections to the base terminals are shown in
Figures 1 and 2.

Base and Mounting-This vacuum tube employs a {our-pin bayonet type base having special
Contact metal at the ends of the pins. It is suitable for use in a Western Electric 100L, 100R, or
similar type socket, preferably provided with contact-metal contacts.

The tube may be mounted in either a vertical or horizontal position. If mounted in a horizontal
position the plane of the filament, which is indicated in Figure 2, should be vertical. To assure
adequate ventilation the tubes should be mounted with not less than 2% inches between centers
when two or more tubes are used.

Average Direct Interelectrode Capacitances

Grid to plate , . .................................... 5.1 Mf
Grid to filament . , r ....................... 4 9 wtf
Plate to filament . ............................. 2 7 [inf

These values are for :1 based tube without socket.

Copyright 1939 Western Electric Company, Incorporated

101FA

Page 2

IOIFA

Filament Rating
Filament current .............................. . . 0.50 ampere, d.c.
Nominal filament voltage ........................... 4.15 volts

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

The filament resistance of this tube increases slightly during the first 2000 hours of operation.
The voltage given above is the nominal value after this resistance change has stabilized.

Characteristics-Typical curves showing plate current as a function of grid voltage for several
values of plate voltage are shown in Figure 3. The grid and plate voltages are measured from the
negative end of the filament. Corresponding amplification factor, plate resistance and transcon-
ductance characteristics are given in Figures 4, 5 and 6 respectively. Plate current as a function
of plate voltage for several values of grid voltage is shown in Figure 7.

Operating Conditions and Output-Permissible operating plate and grid voltages are in-
cluded within the area, ABCD in Figure 3. A number of recommended and maximum operating
conditions and the corresponding values of amplification factor, plate resistance and performance
data are given in the table below. Recommended conditions or others of no greater severity should
be selected in preference to maximum conditions wherever possible. The life of the tube at maximum
operating conditions may be shorter than at less severe conditions.

The performance data shown includes the fundamemal power output in milliwatts and the
second and third harmonic levels in db below the fundamental for values of load resistance equal
to the plate resistance and for a load resistance of 12000 ohms. The peak value of the sinusoidal
input voltage Em, which gives the indicated output Pm, and harmonic levels F2, and Fan, in
each case is numerically equal to the grid bias. For a smaller input voltage E3, the approximate
levels may be computed from the following relations:

5"
I

Em
-_ _ F2111 +2010g10Ez+

E
F3 = F3, + 40 log, E-g
E

)Iicrophonic Noise

For a plate voltage of 130 volts, a grid bias of -8 volts, and a load resistance of 100,000 ohms,
the mean microphonic output level of this tube, measured in a laboratory reference test set is 30 db
below 1 volt. The range of levels of individual tubes extends from 20 to 40 db below 1 volt. Since
microphonic noise output 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 types
of tubes which have been tested in the same way.

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