K6MCO Calculators

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Ohm's Law

Voltage:

Resistance:

Current:

E = I R
R = E / I
I = E / R

Capacitive Impedance

Capacitance:

Frequency:

Reactance:

-Im(Z)

Z = 1 / 2 π f C

Inductive Impedance

Inductance:

Frequency:

Reactance:

Im(Z)

Z = 2 π f L

LC Resonance

Inductance:

Capacitance:

Frequency:

f = 1 / 2 π √ L C

Wavelength

Wavelength:

Frequency:

c = λ f

LR Time Constant

Inductance:

Resistance:

Time:

τ = L / R

RC Time Constant

Capacitance:

Resistance:

Time:

τ = R C

Power

Power:

dBm:

dBm

Load:

Voltage (r.m.s.):

V_rms

Voltage (sine peak):

V_peak

P = V_rms² / R
dBm = 10 * log₁₀ (P / 0.001)
V_rms = V_peak / √ 2

Air Wound Coil

Diameter:

Length:

Turns:

Turns per inch:

n / L

Inductance:

μH

μH = d² n² / (18 d + 40 L)
[inch]

Air Gap Capacitor

Area:

Gap:

Breakdown voltage:

V_br

3x safety factor:

# Plates:

Capacitance:

pF = 0.2248 K A (n-1) / d
[inch]

K = 1.0006 for air

V_br = 30 kV / cm
[ideal]

Toroid Inductance

Core:
Inductance index:

A_L

Turns:

Inductance:

μH

L = A_L * n² / 10⁶

[A_L in mH per 1000 turns]

Toroid info

3-digit Capacitor Code

RF Exposure Limits

Frequency:
Tx PEP Out:

Feedline type:
Feedline loss:

Feedline length:

Antenna type:
Antenna gain:

Power to antenna:
EIRP:
ERP:
Separation distance:

Routine exposure evaluation required:

Include ground reflections
Peak power density:

Mode:
Mode duty cycle:

Max Tx per 6 min:
Max Tx per 30 min:

Controlled limits (6 min)
Maximum allowed power density:
Min allowed distance:

Uncontrolled limits (30 min)
Maximum allowed power density:
Min allowed distance:

Evaluating Compliance with FCC Guidelines for Human Exposure to Radiofrequency Electromagnetic Fields: Additional Information for Amateur Radio Stations

ARRL RF Exposure Calculator

2023 Changes to FCC RF Exposure Rules