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Table 452. Values for Power Factor in Percent for Several Electrical Insulating Materials at Radio Frequencies

# Table 452. Values for Power Factor in Percent for Several Electrical Insulating Materials at Radio Frequencies

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434

TABLES 453-465.-RXDIO

P R O P A G A T I O N DATA

*

Antenna a r r a y s (figs. 17-19).-The basis for all directivity control in antenna arrays is wave interference. Ey providing a large number of sources of

radiation, it is possible with a fixed amount of power greatly to reinforce radiation in a desired direction by suppressing the radiation in undesired directions.

The individual sources may be any type of antenna.

The radiation patterns of several common types of individual elements are

shown in figure 17. The expressions hold for linear radiators, rhombics, vees,

horn radiators, or other complex antennas when combined into arrays, provided a suitable expression is used for A,the radiatidn pattern of the individual

dir.cltriy

<""."I

dislribullon

Iyp. of

horizontal

Fi8

ClOl

Holl-wov

dipole

=

fOS

(5

K

I,"

0)

c3s 0

Shortene<

dipole

Lengthene

dipole

Horizonic

loop

FM

z KIII

101 = K

cos @

Horizontc

turnstile

i,and i2

phased 9

0'

0 = horizontal

angle measured from perpendicular bisecting plane

@ = vertical angle measured from horizon

K and K' are constants and K' 2 0.T

FIG.17.-Radiation patterns of several common types of antennas.

antenna. The array expressions are multiplying factors. Starting with an individual antenna having a radiation pattern given by A,the result o f combining

it with similar antennas is obtained by multiplying A by a suitable array factor,

thus obtaining an A' for the group. The group may then be treated as a single

source of radiation. The result of combining the group with similar groups, or,

for instance, of placing the group above ground, is obtained by multiplying A'

by another of the array factors given.

The expressions given here assume negligible mutual coupling between individual antennas. When coupling is not negligible, the expressions apply only

if the feeding is adjusted to overcome the coupling and thus produce resultant

currents that are of the amplitude and relative phases indicated.

* Data arranged by Newbern Smith and Marcella Phillips, Central Radio Propagation

Laboratory, National Bureau of Standards.

(continued)

SMITHSONIAN PHYSICAL TABLES

435

One of the most important arrays is the linear multielement array where a

large number of equally spaced antenna elements are fed equal currents in

phase to obtain maximum directivity in the forward direction. Figure 18 gives

expressions for the radiation pattern of several particular cases and the general

case of any number of broadside elements.

In this type of array a great deal of directivity may be obtained. A large

number df minor lobes, however, are apt to be present, and they may be undesirable under some conditions, in which case a type called the binomial array

may be used. Here again all the radiators are fed in phase but the current is not

distributed equally among the array elements, the center radiators in the art'ay

oonnourwion

A

A

[

* a

sin 0)]

cos

A

+ 2A [cos Iso sin 011

sin (m

A

(general case)

A

c

ti

e)

sin

e)

1 for horizontal loop, vertical dipole

cos

A=

sin

sin

sin

(2

e

C O ~

e

)

for horizontal dipole

so = spacing of successive elements in degrees

FIG.18.-Linear

being fed more current than the outer ones. Figure 19 shows the configuration

and general expression for such an array. I n this case the configuration

is made for a vertical stack of loop antennas in order to obtain single-lobe

directivity in the vertical plane. If such an array were desired in the horizontal

plane, say n dipoles end to end, with the specified current distribution the

expression would be

The term binomial results from the fact that the current intensity in the SUCcessive array elements is in accordance with the binomial expansion (1

I)''-',

where n is the number of elements.

+

(continued)

SMITHSONIAN PHYSICAL TABLES

436

I

'0

of loops in the array

FIG.19.--Development of binomial array.

C O N S T A N T O F N O N P O L A R GASESlM

T A B L E 453.-DIELECTRIC

at 0°C and 76cmHg

~

Gas

(K-l)xlOB

........ 69.2

Neon .......... 134.1

Argon ......... 554.2

Helium

Gas

(K-I) x 10%

Gas

(K-1) xlOe

Hydrogen

Carbon dioxide.. 988

Oxygen

...... 272

........ 532.5

Air (COZ free). . 570

Nitrogen

....... 580

*m Jelatis, J. G., Journ. Appl. Phys., vol. 19, p. 419, 1948; Hecter, L. G., and Woernley, D. C., Phys.

Rev., vol. 69, p. 101, 1946.

SMITHSONIAN PHYSICAL TABLES

437

T A B L E 454.-DIELECTRIC

C O N S T A N T A N D LOSS T A N G E N T O F DIELECTRIC

M A T E R I A L S 15'

The following table presents values of dielectric constant,' e' (relative to that vacuum € 0 ) and

loss tangent, tan 8, for various substances at the frequencies and temperatures indicated. The loss

tangent, tan 6, is identical with the power factor, cos 0 (or sin a), for low loss substances. The

table shows it multiplied by lo'.

Part 1.-Solids

Tzmp.

C I

Materials

A. Inorcanic

1. Crystals

Ice'* .........................

Sodium chloride*

-12

...............

2. Ceramics

a. Steatite bodies

AlSiMag 211'

25

25

...............

lo5 ............

26

.....

25

............ ...

Corning No. 1990' ..............

Foamglas' .....................

Fused quartz" .................

20

Mycalex K

Porcelain, dry process"

3. Glasses

Corning No. 790'

Melmac resin 592"

........

d. Urea-formaldehyde

I

E'/B

d/eo

24

23

25

25

5.90

<1

6.00

92

5.98

34

5.97

5

5.96

4

5.4

5.4

5.4

5.4

25

d / ~ o 9.5

tan6

170

e'/eo

5.50

tan6

220

6

3

9.3

125

5.36

140

9.0

26

5.08

75

3.85

d / ~ o 3.85

6

tan6

6

d / ~ 8.40

8.38

tan6

4

4

d / ~ o 90.0

82.5

tan6 1500 1600

3.78

d/eo

3.78

7.5

tan 6 8.5

3.85

6

8.30

5

17.5

3180

3.78

2

2.85

19

2.85

3

5.05

190

5.23

230

4.87

160

5.15

165

4.72

4.64

160

d/eo

25

a'/€,

tan6

26

27

e'/e

tan6

E'/Q

tan6

.....

24

Nylon 610" ...............

25

Nylon 610" ...............

90% humidity ...........

25

d/~o

tan6

d/eo

tan6

d/~o

tan6

11.3**

40

5.04

78

4.74

156

3.78

1

4.60

340

4.62

56

4.04

570

4.52

82

3.59

700t

4.55

137

4.37

62

4.30

77

4.25

124

6.15

400

6.70

590

6.00

119

6.25

470

5.75

115

5.20

347

5.5

200

4.70

360

4.59

434

7.1

380

6.7

280

6.0

310

5.2

500

4.65

782

3.60

155

4.5

650

3.50

186

4.2

640

3.14

218

3.2

380

3.0

200

3.0

220

~'/g

tan6

2

5.90

14

3.82

9.4

7.94

42

5.49

455

3.78

1

tan 6

d/eo

3.17

7

5.90

5

5.90

<1

d/eo

tan6

26

1x100 1x108 1x1010

4.15

1200

5.90

<2

-

tan6

24

1x103

e'le,,

tan 6

tan6

B. Organic, with or without inorganic components

1. Crystals

Naphthalene" ..............

25

2. Plastics

a. Phenol-formaldehyde

Bakelite BM-169811a .......

(powder preheated) .....

Formica XX" ............

(field 1 t o laminate) ....

b. Phenol-aniline-formaldehyde

Resinox 7013" ............

(preformed and preheated)

c. Melamine-formaldehyde

(sheet stock) ............

ixio*

tan6

.............

b. Miscellaneous

Ruby mica'

Frequency, cycles per second

72

8.20

9

m These data were selected from Tables of Dielectric Materials, volume 3, Laboratory of Insulation Research,

Massachusetts Institute of Technology Cambridge Mass. June 1918.

a c is used for dielectric constant in' this table 6 the piace of K.

Numbers refer to notes at end of table.

** Not corrected for variations of density.

t Rod stock in HLI (TE11) made of circular wave guide.

(continued)

SMITHSONIAN PHYSICAL TABLES

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Table 452. Values for Power Factor in Percent for Several Electrical Insulating Materials at Radio Frequencies

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