Formulas on the General Exam
This page contains all the formulas needed for the General class ham radio license exam. You might want to print out these formulas and review them just before entering the exam room, but leave this sheet in the car! Do not bring it into the exam room with you!
| International System of Units (SI) |
Prefix
name |
Prefix
symbol |
Value |
| giga- |
G |
109 |
1,000,000,000 |
one billion |
| mega- |
M |
106 |
1,000,000 |
one million |
| kilo- |
k |
103 |
1,000 |
one thousand |
| (none) |
(none) |
100 |
1 |
one |
| centi- |
c |
10−2 |
.01 |
one one-hundredth |
| milli- |
m |
10−3 |
.001 |
one one-thousandth |
| micro- |
µ |
10−6 |
.000001 |
one one-millionth |
| nano- |
n |
10−9 |
.000000001 |
one one-billionth |
| pico- |
p |
10−12 |
.000000000001 |
one one-trillionth |
Standing wave ratio:
$$ SW\!R = \frac{highest\text{-}impedance}{lowest\text{-}impedance} $$
Length of 1/2 wavelength antenna:
$$ Length~ \text{(in feet)} = \frac{468}{Frequency~ \text{(in MHz)}} $$
Length of 1/4 wavelength antenna:
$$ Length~ \text{(in feet)} = \frac{234}{Frequency~ \text{(in MHz)}} $$
Resistors in parallel:
$$ \frac{1}{R_t} = \frac{1}{R_1} + \frac{1}{R_2} + \frac{1}{R_3} $$
Inductors in series:
$$ L_t = L_1 + L_2 $$
Equal-value inductors in parallel:
$$ L_t = \frac {L_i}{n} $$
Capacitors in parallel:
$$ C_t = C_1 + C_2 + C_3 $$
Equal-value capacitors in series:
$$ C_t = \frac {C_i}{n} $$
Capacitors in series:
$$ \frac {1}{C_t} = \frac {1}{C_1} + \frac {1}{C_2} $$
Transformers:
$$ E_s = E_p \times \frac {N_s}{N_p} $$
$$ \frac {N_P}{N_S} = \sqrt{\frac {Z_P}{Z_S}} $$
RMS voltage:
$$ V_P = \frac{V_{RMS}}{0.707} $$
$$ V_{PP} = V_P \times 2 $$
$$ V_{RMS} = V_P \times 0.707 $$
Ohm's Law:
$$ R = \frac {E}{I} $$
Power:
$$ P = E \times I $$
$$ P = \frac {E^2}{R} $$
$$ P = I^2 \times R $$
$$ E = \sqrt{P \times R} $$
Peak envelope power:
$$ V_P = \frac{V_{PP}}{2} $$
$$ V_{RMS} = V_P \times 0.707 $$
$$ PEP = \frac{{V_{RMS}}^2}{R} $$
Decibel math:
$$ loss\text{-}\!factor = 10 ^ \left( \large \frac{-loss \text{-} in \text{-} db}{10} \right) $$
$$ percent \text{-}loss = ( 1 - loss\text{-}\!factor ) \times 100\% $$
Frequency modulation:
$$ bandwidth = 2 \times \left(D_{MAX} + M_{MAX}\right) $$
Upconverter:
$$ multiplier = \frac {transmitted \text{-}frequency}{lower \text{-}frequency} $$
$$ lower \text{-}frequency \text{-}maximum \text{-}deviation = \frac {transmitted \text{-}frequency \text{-}maximum \text{-}deviation}{multiplier} $$
