4S6TMP.com
Free RF, Electronics & Amateur Radio Engineering Tools
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📡 RF & Antenna
🔧 Electronics
📻 Amateur Radio
📡 RF & Antenna Design
Dipole Antenna Calculator
Length, gain, impedance for any band
Calc
Design
Ground-Plane / Vertical / J-Pole
Vertical antenna designs and dimensions
Calc
Design
Loop Antenna Calculator
Full-wave and magnetic loop dimensions
Calc
Design
Antenna Gain Converter
Convert between dBi, dBd, and linear gain
Calc
Ref
Coax Loss Calculator
Attenuation vs frequency for common cables
Calc
Ref
VSWR / Return Loss Converter
VSWR, return loss, reflection coefficient
Calc
Ref
Smith Chart Impedance Matcher
L-network, stub matching solutions
Calc
Design
Attenuator Pad Calculator
Pi and T attenuator resistor values
Calc
Design
Quarter-Wave Transformer
Impedance transformer and stub matching
Calc
Design
Microstrip Impedance Calculator
PCB trace width for target impedance
Calc
Design
LC Filter Designer
Low-pass, high-pass, band-pass designs
Calc
Design
Directional Coupler Calculator
Stripline coupler design parameters
Calc
Design
Toroid Inductor Calculator
Turns count for target inductance
Calc
Design
Crystal Oscillator Calculator
Pierce oscillator component values
Calc
Design
PLL / VCO Calculator
Divider ratios, loop filter values
Calc
Design
Path Loss / Link Budget
Free-space path loss and link margin
Calc
Ref
Propagation Predictor
MUF, critical frequency, band openings
Calc
Ref
Grayline Map
Sunrise/sunset terminator for DX
Util
Ref
Grid Square Lookup
Maidenhead locator from coordinates
Util
Ref
Auroral Activity Dashboard
Kp index, solar wind, aurora status
Util
Ref
NVIS Calculator
Antenna height for near-vertical incidence
Calc
Design
Sri Lankan Repeater Directory
VHF repeaters, RSSL infrastructure & daily net schedule
Util
Ref
Satellite Pass Predictor
ISS, amateur satellite visibility
Calc
Util
WSPR / FT8 Spot Viewer
Decode spots and check propagation
Util
Ref
ERP / EIRP Calculator
Effective radiated power from TX power and gain
Calc
Ref
Frequency ↔ Wavelength
Convert between frequency and wavelength
Calc
Ref
Noise Figure Calculator
Cascaded noise figure for receive chains
Calc
Design
RF Power Density Calculator
RF exposure estimate at distance
Calc
Ref
🔧 Electronics & Circuit Design
Resistor Color Code
4/5/6 band resistor decoder
Calc
Ref
PCB Trace Width Calculator
Current capacity and temperature rise
Calc
Design
LED Resistor Calculator
Series resistor for LEDs
Calc
Design
SMD Decoder
Resistor and capacitor code lookup
Util
Ref
SMPS Converter Calculator
Buck, boost, buck-boost design
Calc
Design
Ham Radio Battery Calculator
12V runtime for POTA, Field Day & emergency ops
Calc
Util
Wire Gauge Calculator
AWG, SWG, mm² conversion and current
Calc
Ref
Timer / PWM Calculator
Arduino, STM32, ESP32 register values
Calc
Design
Baud Rate Calculator
UART, SPI, I2C timing and error
Calc
Design
Decibel Calculator
Power, voltage, current dB conversions
Calc
Ref
📻 Amateur Radio Utilities
Web Logbook
Local QSO logging with ADIF export
Util
QSL Generator
Printable QSL card generator
Util
Solar Weather Dashboard
SFI, SSN, A-index, K-index live data
Util
Ref
CTCSS / DCS Reference
Tone codes and frequencies table
Ref
Go-Kit Planner
Emergency radio kit checklist
Util
Net Control Script
Generate net control scripts
Util
NIMS Message Form
ICS-213 message form generator
Util
Award Tracking
Track DXCC, WAS, WAZ progress
Util
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