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Radio Valves

Heater Data for Some Early Valves

This table was extracted from "Amateur Wireless" No 122, 4th. of October, 1924.

Maker Type of Valve Filament Voltage Filament Amperes H.T. Voltage Purpose
B.T.H. B3 2.0 0.35 20-80 General
B4 6.0 0.25 40-100 Detector and Low Frequency
B5 2.5-3 0.06 20-80 General
R 4.0 0.63 45-60 General
Cossor P1 3.5 0.73 20-80 Detector and Low Frequency
P2 3.5 0.73 20-80 High Frequency
Cossor "Wuncell" W1 1.6-1.8 0.3 30-70 Detector and Low Frequency
W2 1.6-1.8 0.3 30-70 High Frequency
Dextraudion 1.0 0.1 20-150 General
Ediswan AR 4.0 0.75 30-80 General
R 4.0 0.75 50-100 General
ARDE 1.8-2.0 0.3 20-50 General
AR06 2.5 0.06 20-50 General
PV1 6.0 1.5 300-600 Low Frequency
PV2 6.0 1.5 200-400 Low Frequency
PV3 4.0 0.7 70-110 Low Frequency
PV5DE 5.0 0.25 50-150 Low Frequency
G.W.I. A1 4.6 0.45 50-200 Low Frequency
G1 4.0-6.0 0.45 50-120 High Frequency and Detector
Louden (Plain) 4.8-5.0 0.4 40-80 Detector and Low Frequency
(Blue) 4.8-5.0 0.4 40-80 High Frequency
Marconi Osram DER 1.8 0.4 30-70 General
DEQ 3.0 0.2 24 High or Low Frequency
DEV 3.0 0.2 24 High or Low Frequency
DE3 2.4-3 0.06 30-80 General
DE4 3.6 0.32 30-150 General and Low Frequency
DE5 5.0, 0.25 30-150 Low Frequency
DE6 1.8 0.4 30-150 Low Frequency
FE1 4.5 1.5 24-100 Four-electrode
FE2 4.5 1.5 24-100 Four-electrode
LS1 6.0 1.5 300-600 Low Frequency
LS2 6.0 1.5 300- 600 Low Frequency
LS3 4.0 0.65 70-100 Low Frequency
LS5 4.5 0.8 150 Low Frequency
Q 5.0 0.45 25-200 Low Frequency
QX 5.0 0.75 25-100 Detector
R 4.0 0.67 70 General
R4B 3.8 0.65 50-70 General
R4C 3.8 0.65 50-70 General
R5V 5.0 0.65 30-150 General
V24 5.0 0.75 24-30 High Frequency
Mullard DF 2.0-3.0 0.06 20-100 General
DFA0 3.5 0.35 30-40 Low Frequency
DFA1 5.5 0.2 30-40 Low Frequency
DFA2 3.5 0.25 20-25 Low Frequency
LF Ora A 1.4 0.2 20-50 General
LF Ora B 1.4 0.3 20-50 General
LF Ora C 1.4 0.4 20-50 General
1-volt Ora 1.0 0.25 30-150 General
Ora A 3.8 0.62 20-50 General
Ora B 3.8 0.62 20-50 General
PA1 6.0 1.5 200-400 Low Frequency
PA2 5.5 0.85 100-200 Low Frequency
PA3 4.0 0.67 70-120 Low Frequency
RA 3.8 0.67 50-80 Detector and Low Frequency
S3 6.0 0.65 15-30
Myers 4.0 0.6 20-300 General
DE 2.5 0.25 20-300 General
Penton HE2 General
HE4 5.0 0.15 60 General
Thorpe K1 5.0 0.42 50-100 General
K4 Four-electrode
Wecovalve 0.8-1.1 0.25 17-45 Detector and Low Frequency
Xtraudion 4.0 0.4 30-70 General

The following data for the bright and dull emitters was extracted from "A First Course in Wireless" by Robert W. Hutchinson, University Tutorial Press, 1926., p. 151. This data was probably acquired by measurement of samples rather than from manufacturers published data. Data for the Marconi R4c and R5 have been corrected from other sources. Other data is from manufacturer's publications.

Data is given for bright emitter, pure tungsten filament valves and for thoriated tungsten 'dulls'. These two classes are further separated into those designed to work from one, two or three lead acid accumulator cells (~2, 4 or 6 volts). Most were designed to be operated with a series filament rheostat of about 5 or 10 ohms. This allowed for some adjustment as the cells discharged.

For comparison similar data is given for representative examples of 'azide process' and oxide coated cathode valves.

The cold resistance should be considered a rough approximation as it makes no allowance for differences in operating temperatures and powers, or for wiring and connection resistances, which may be significant at these low voltages and high currents.

I hope this information may be of some use to any collector who wishes to 'light up' one of these, by now, rather valuable artifacts.

Bright Emitters

Two Cell

Name Filament Current
amps
Filament Voltage
volts
Filament Power
watts
Filament Resistance(hot)
ohms
Filament Resistance(cold)
ohms
Mullard Red Ring 0.6 3.2 1.92 5.3 0.40
B.T.H. R 0.63 4 2.52 6.3 0.47
Mullard Ora A & B 0.65 3.4-3.8 2.47 5.8 0.43
Marconi-Osram R.4C. 0.5 3.8 1.9 7.6 0.56
Marconi-Osram R. 0.7 4 2.80 5.7 0.42
Ediswan A.R. & R. 0.75 4 3.00 5.3 0.40

Three Cell

Name Filament Current
amps
Filament Voltage
volts
Filament Power
watts
Filament Resistance(hot)
ohms
Filament Resistance(cold)
ohms
Marconi-Osram R.5 0.7 3.8 2.66 5.4 0.40
Cossor P1 & P2 0.75 4-4.5 3.38 6.0 0.44
Marconi-Osram Q.X. 0.75 5 3.75 6.7 0.49
Marconi-Osram V.24 0.75 5 3.75 6.7 0.49
Marconi-Osram FE1 & FE2 1.5 4.5-5 7.50 3.3 0.25
Marconi-Osram L.S.1 & L.S.2 1.5 6 9.00 4.0 0.30

Dull Emitters

One Cell

Name Filament Current
amps
Filament Voltage
volts
Filament Power
watts
Filament Resistance(hot)
ohms
Filament Resistance(cold)
ohms
Met.-Vick. D.2 0.25 1.1 0.28 4.4 0.44
Ediswan A.R.D.E. 0.3 1.8-2 0.60 6.7 0.67
Cossor W.1 & W.2 0.3 1.8-2 0.60 6.7 0.67
Cossor W.R.1 & 2 0.3 1.8-2 0.60 6.7 0.67
Mullard D.3 H.F. 0.3 1.8-2 0.60 6.7 0.67
Mullard D.3 L.F. 0.3 1.8-2 0.60 6.7 0.67
B.T.H. B.3 0.35 2 0.70 5.7 0.57

Two Cell

Name Filament Current
amps
Filament Voltage
volts
Filament Power
watts
Filament Resistance(hot)
ohms
Filament Resistance(cold)
ohms
Ediswan A.R.06 0.06 3 0.18 50.0 5.00
Mullard D.06 H.F. 0.06 3 0.18 50.0 5.00
Mullard D.06 L.F. 0.06 3 0.18 50.0 5.00
Economic '06 0.06 3 0.18 50.0 5.00
B.T.H. B.5 0.06 3.8-4 0.24 66.7 6.67
Marconi-Osram D.E.3 0.06 2.4-3 0.18 50.0 5.00
Marconi-Osram D.E.Q. 0.2 3 0.60 15.0 1.50

Azide Process

Name Filament Current
amps
Filament Voltage
volts
Filament Power
watts
Filament Resistance(hot)
ohms
Filament Resistance(cold)
ohms
Mullard PM3 0.075 4 0.30 53.3 11.85
Mullard PM1A 0.1 2 0.20 20.0 4.5
Mullard PM2A 0.2 2 0.40 10.0 2.22
Mullard PM5X 0.075 6 0.45 80.0 18

Oxide Coated

Name Filament Current
amps
Filament Voltage
volts
Filament Power
watts
Filament Resistance(hot)
ohms
Filament Resistance(cold)
ohms
Cossor 210LF 0.1 2 0.20 20.0 4.5
Cossor 220P 0.2 2 0.40 10.0 2.25
Osram LP2 0.2 2 0.40 10.0 2.25
Osram HL2 0.1 2 0.20 20.0 4.5

Amongst suitable dull emitters for 4 volt batteries are B.T.H. B.5 (filament consumption 0.06), Marconi-Osram D.E.4 (filament consumption 0.32), Mullard D.F.A. 0 (filament consumption 0.35), etc.

Resistance versus Temperature for Tungsten Filaments

with some cold resistance measurements for some example valves.

The resistivity of Tungsten increases almost linearly with temperature between 300 and 3500 kelvins (°C plus 273.15). Bright emitters operate at 2500 - 2600 K, dull emitters at 1900 - 2100 K and oxide coated cathodes at 950 - 1050 K. (Note that Kelvins are units in themselves not degrees of a scale. It is incorrect to write °K.)

The cold resistance of a filament may be multiplied by about 4.5 (range 3.8 - 5.0) for an oxide cathode at its working temperature. The ratios for dulls and brights are ~10 (range: 9.4 - 10.6) and ~13.5 (range: 13 - 13.7) respectively.

Temperature
Kelvins
Relative resistance
R/R300 K
Resistivity
μΩ·cm
Cathode Types
300 1.0 5.65
400 1.43 8.06
500 1.87 10.56
600 2.34 13.23
700 2.85 16.09
800 3.36 19.00
900 3.88 21.94
1000 4.41 24.93 Oxide cathodes
1100 4.95 27.94
1200 5.48 30.98
1300 6.03 34.08
1400 6.58 37.19
1500 7.14 40.36
1600 7.71 43.55
1700 8.28 46.78
1800 8.86 50.05
1900 9.44 53.35
2000 10.03 56.67 Dull Emitters
2100 10.63 60.06
2200 11.24 63.48
2300 11.84 66.91
2400 12.46 70.39
2500 13.08 73.91 Bright Emitters
2600 13.72 77.49
2700 14.34 81.04
2800 14.99 84.70
2900 15.63 88.33
3000 16.29 92.04
3100 16.95 95.76
3200 17.62 99.54
3300 18.28 103.3
3400 18.97 107.2
3500 19.66 111.1
3600 26.35 115.0

© Andy Cowley, 2005-2012     Home

This page last modified by AJC on Monday, 29-Mar-2010