RADIO CALCULATIONS
by Harry Lythall

Here are a few calculators for electronic/radio circuits. They are crude, but they work.

Note that the inductance unit is nano-Henries (nH) (1uH = 1000nH). Capacitance unit is pico-Farads (pf) and resistance unit is ohms. Decimals are not allowed in the input fields, if you enter a value of 1.9925 then the assumed input value will be 1.

Resistors In Series (or Capacitors in Parallel)

Just add them together!

Resistors In Parallel (or Capacitors in Series)

Formula: Effective Resistance = (R1 x R2) / (R1 + R2)

Reactance of a Capacitor

Formula: Reactance = 1 / (2 * Pi * F * C)

Reactance of an Inductor

Formula: Reactance = 2 * Pi * F * L

Basic frequency

Formula: Frequency = 1 / (2 * Pi * Sqrt(LC))

Single Layer Coil

Formula:

Multi-Layer Coil

Formula:

Heatsink Evaluation

Calculates the effective temperature rise coefficient of a measured heatsink. Area is EXPOSED surface area of heatsink in square centimeters.

Formula: Degrees Centigrade per Watt = 50 / Sqrt(Area sq-cm )

Heatsink Calculation

Calculates heatsink surface area needed for a given heatsink temperature coefficient.

Formula: Area Required (sq-cm) = Sq (50/C-watt)

Attenuators - "T" and "H" Type

Formulas:

The Input/Output powers may be in any electrical unit you prefer, eg: Meggawatts, Picowatts, Joules, Hamster-treadmill revolutions per hour etc.

Negative values of resistance occur when impossible values of input and output impedance and attenuation are entered. For example, it is not possible to drive a 50-ohm line from a 600-ohm line and have a voltage attenuation factor of less than 6.78

Attenuators - Square (or Box) Type