CONSTANTS, CONVERSIONS and CHARACTERS

RULE OF THUMB FOR ESTIMATING DISTANCE TO LIGHTNING / EXPLOSION:

km - Divide 3 into the number of seconds which have elapsed between seeing the flash and hearing the noise.
miles - Multiply 0.2 times the number of seconds which have elapsed between seeing the flash and hearing the noise.

Note: Sound vibrations cause a change of density and pressure within a media, while electromagnetic waves do not. An audio tone won't travel through a vacuum but can travel at 1100 ft/sec through air. When picked up by a microphone and used to modulate an EM signal, the modulation will travel at the speed of light.

THE SPEED OF LIGHT
ACTUAL VALUE UNITS RULE OF THUMB
2.9979246 x 10 8 m/sec 3 x 10 8
299.79 m/usec 300
3.27857 x 10 8 yd/sec 3.28 x 10 8
5.8275 x 10 8 NM/hr 5.8 x 10 8
1.61875 x 10 5 NM/sec 1.62 x 10 5
9.8357105 x 10 8 ft/sec 1 x 10 9
9.8357105 x 10 2 ft/usec 1 x 10 3

SPEED OF LIGHT IN VARIOUS MEDIUMS

The speed of EM radiation through a substance such as cables is defined by the following formula:

V = c / (u r e r) 1/2

Where: u r = relative permeability and e r = relative permittivity
The real component of e r = dielectric constant of medium.
EM propagation speed in a typical cable might be 65-90% of the speed of light in a vacuum.

* The speed remains constant until 82,000 ft, when it increases linearly to 1215 km/hr (755 mph, 656 kts) at 154,000 ft. Also see Mach number section for discussion of Calibrated Air Speed (CAS) and True Airspeed (TAS) and a plot of the speed of sound vs altitude.

SPEED OF SOUND IN VARIOUS MEDIUMS
SUBSTANCE SPEED (ft/sec)
Vacuum Zero
Air 1,100
Fresh Water 4,700
Salt Water 4,900
Glass 14,800
Steel 20,000

FUNDAMENTAL PHYSICAL CONSTANTS
PHYSICAL CONSTANT QUOTED VALUE S* SI UNIT SYMBOL
Avogadro constant

Bohr magneton

Boltzmann constant

6.0221367 x 10 23

9.2740154 x 10 -24

1.380658 x 10 -23

36

31

12

mol -1

JT -1

JK -1

NA

u B

k(=R N A)

Electron charge

Electron specific charge

Electron rest mass

1.602177 33 x 10 -19

-1.758819 62 x 10 11

9.1093897 x 10 -31

49

53

54

C

Ckg -1

kg

-e

-e/m e

m e

Faraday constant

Gravity (Standard Acceleration)
.

Josephson frequency to voltage ratio

9.6485309 x 104

9.80665 or
32.174

4.8359767 x 1014

29

14

.

.

Cmol-1

m/sec 2 or
ft/sec 2

HzV -1

F

g
.

2e/h

Magnetic flux quantum

Molar gas constant

Natural logarithm base

Newtonian gravitational constant

2.06783461 x 10 -15

8.314510

2.71828

6.67259 x 10 -11

61

70

-

85

Wb

Jmol -1 K -1

dimensionless

m 3 kg -1 s -2

Phio

R

e

G or K

Permeability of vacuum

Permittivity of vacuum

Pi

4pi x 10 -7

8.8541878 x 10 -12

3.141592654

d

d

H/m

F/m

dimensionless

u o

e o

Pi

Planck constant

Planck constant/2

Quantum of circulation

Radius of earth (Equatorial)
.

Rydberg constant

6.62659 x 10 -34

1.05457266 x 10 -34

3.63694807 x 10 -4

6.378 x 10 6 or
3963

1.0973731534 x 10 7

40

63

33

-
-

13

Js

Js

Jskg -1

m or
miles

m -1

h

h(=h2)

h/2m e

-
-

R x

Speed of light

Speed of sound
(dry air @ std press & temp)

Standard volume of ideal gas

Stefan-Boltzmann constant

2.9979246 x 10 8

331.4
.

22.41410 x 10 -3

5.67051 x 10 -8

1

-
.

19

19

ms -1

ms-1
.

m 3mol -1

WK -4 m -2

c

-
.

V m

sigma

* S is the one-standard-deviation uncertainty in the last units of the value, d is a defined value.
(A standard deviation is the square root of the mean of the sum of the squares of the possible deviations)

Note: The International Maritime Organization agreed to officially stop Morse code use by February 1999, however use may continue by ground based amateur radio operators (The U.S. Coast Guard discontinued its use in 1995)

DECIMAL / BINARY / HEX CONVERSION TABLE

Decimal Binary Hex . Decimal Binary Hex . Decimal Binary Hex
1 00001 01h . 11 01011 0Bh . 21 10101 15h
2 00010 02h . 12 01100 0Ch . 22 10110 16h
3 00011 03h . 13 01101 0Dh. 23 10111 17h
4 00100 04h. 14 01110 0Eh. 24 11000 18h
5 00101 05h. 15 01111 0Fh. 25 11001 19h
6 00110 06h. 16 10000 10h. 26 11010 1Ah
7 00111 07h. 17 10001 11h. 27 11011 1Bh
8 01000 08h. 18 10010 12h. 28 11100 1Ch
9 01001 09h. 19 10011 13h. 29 11101 1Dh
10 01010 0Ah. 20 10100 14h. 30 11110 1Eh

When using hex numbers it is always a good idea to use "h" as a suffix to avoid confusion with decimal numbers.

To convert a decimal number above 16 to hex, divide the number by 16, then record the integer resultant and the remainder. Convert the remainder to hex and write this down - this will become the far right digit of the final hex number. Divide the integer you obtained by 16, and again record the new integer result and new remainder. Convert the remainder to hex and write it just to the left of the first decoded number. Keep repeating this process until dividing results in only a remainder. This remainder will become the left-most character in the hex number (after converting to hex of course).

For example, to convert 60 (decimal) to hex, we have 60/16=3 with 12 remainder. 12 is C (hex) - this becomes the right-most character. Then 3/16=0 with 3 remainder. 3 is also 3 (hex). This becomes the next (and final) character to the left in the hex number, so the answer is 3C h.

BASIC MATH / GEOMETRY REVIEW

A radian is the angular measurement of an arc which has an arc length equal to the radius of the given circle, therefore there are 2 radians in a circle. One radian = 360° /2 = 57.296....°


Return to: EW & Radar Handbook Home Page | Table of Contents