Coax loss & recommendation
Compare common 50-ohm cables for your frequency, length and power.
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24 calculators shown
Quick access
Use calculators on this pageChoose a calculator
Browse by category or use the search controls above to reach the right radio tool quickly.
Repeaters & gateways
2 toolsFind systems and calculate repeater frequencies
Repeaters & gatewaysRepeater Input and Output Frequency CalculatorCalculate a repeater input or output frequency from a known frequency and signed shift.Open calculator
Repeaters & gatewaysUK Repeater and Gateway Finder by PostcodeFind nearby UK repeaters and gateways with distance, beam direction, frequencies, modes and access details.Open calculatorLocation & mapping
3 toolsPostcodes, coordinates, Maidenhead locators and WAB squares
Location & mappingUK Postcode to Maidenhead Locator CalculatorConvert a UK postcode centre into a Maidenhead locator, coordinates, National Grid reference and map position.Open calculator
Location & mappingCoordinates to Maidenhead Locator CalculatorConvert WGS84 latitude and longitude into a six-character Maidenhead locator, with optional device GPS.Open calculator
Location & mappingWAB Square Calculator from Postcode, Locator or GPSFind a 10 km Worked All Britain square from a UK postcode, Maidenhead locator or device GPS position.Open calculatorAntenna & feedline
5 toolsAntenna dimensions, coax, matching and adjustment
Antenna & feedlineCoax Loss and Cable Recommendation CalculatorCompare estimated feedline loss, delivered power and suitability for common 50-ohm coax cables.Open calculator
Antenna & feedlineHam Radio Antenna Length CalculatorCalculate starting lengths for dipoles, quarter-wave verticals, 5/8-wave elements and full-wave loops.Open calculator
Antenna & feedlineWavelength and Coax Stub Length CalculatorCalculate free-space wavelength and physical full, half or quarter-wave coax stub lengths.Open calculator
Antenna & feedlineVSWR, Return Loss and Reflected Power CalculatorConvert VSWR into return loss, reflected-power percentage and mismatch loss.Open calculator
Antenna & feedlineAntenna Trim Correction CalculatorEstimate a corrected antenna element length from measured and target resonant frequencies.Open calculatorRF & propagation
8 toolsPower, radio paths, coverage and signal calculations
RF & propagationEIRP and ERP Power CalculatorCalculate antenna power, EIRP and ERP after feedline loss and antenna gain.Open calculator
RF & propagationWatts to dBm and dBm to Watts ConverterConvert radio-frequency power between watts, milliwatts and dBm.Open calculator
RF & propagationFree-Space Path Loss and Link Budget CalculatorEstimate free-space path loss and ideal received power for a radio link.Open calculator
RF & propagationFresnel Zone Clearance CalculatorCalculate first Fresnel-zone radius and recommended 60 percent clearance along a radio path.Open calculator
RF & propagationRadio Horizon and Line-of-Sight CalculatorEstimate smooth-Earth radio and geometric horizon distance from two antenna heights.Open calculator
RF & propagationMaidenhead Locator Distance and Bearing CalculatorCalculate great-circle distance and initial bearing between two Maidenhead grid locators.Open calculator
RF & propagationForward and Reflected RF Power CalculatorEstimate reflected and delivered RF power from forward power and VSWR.Open calculator
RF & propagationdB Gain and Loss Chain CalculatorAdd RF gains and losses and calculate final watts and dBm through a system chain.Open calculatorRadio workshop
6 toolsElectronics, batteries and station power wiring
Radio workshopOhm's Law CalculatorCalculate voltage, current, resistance and power from two known electrical values.Open calculator
Radio workshopLC Resonant Frequency CalculatorCalculate the resonant frequency and period of an inductor and capacitor.Open calculator
Radio workshopInductive and Capacitive Reactance CalculatorCalculate and compare inductive reactance XL and capacitive reactance XC at a selected frequency.Open calculator
Radio workshopRadio Battery Runtime CalculatorEstimate portable radio operating time from battery capacity, current, duty cycle and usable capacity.Open calculator
Radio workshopDC Cable Voltage Drop CalculatorEstimate voltage drop, delivered voltage and cable heating in radio power wiring.Open calculator
Radio workshopResistor Voltage Divider CalculatorCalculate unloaded or loaded voltage-divider output, current and effective lower resistance.Open calculatorRepeaters & gateways 2 tools
Find and configure nearby radio systems
Antenna & feedline 5 tools
Plan the RF path from radio to antenna
Antenna cutting length
Starting dimensions for common wire and vertical antennas.
Total starting length--
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Wavelength & coax stub
Free-space wavelength and physical cable stub length.
Physical coax stub--
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VSWR & return loss
Convert standing-wave ratio into reflected power and mismatch loss.
Return loss--
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RF & propagation 8 tools
Understand power, paths and coverage
RF power, EIRP & ERP
Allow for feedline loss and antenna gain.
Estimated EIRP--
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Watts & dBm converter
Convert RF power in either direction.
Converted power--
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Path loss & link budget
Ideal free-space loss and estimated received power.
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Fresnel zone clearance
First Fresnel-zone radius at a point along a radio path.
First-zone radius--
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Radio horizon
Smooth-Earth line-of-sight estimate between two antennas.
Typical radio horizon--
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Maidenhead locator distance & bearing
Calculate the great-circle direction and distance between two 4- or 6-character grid locators.
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Radio workshop 6 tools
Electronics, power and station wiring
Ohm's law
Calculate voltage, current, resistance and power.
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LC resonance
Find the resonant frequency of an inductor and capacitor.
Resonant frequency--
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Inductive & capacitive reactance
Compare XL and XC at a chosen frequency.
Inductive reactance--
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Battery runtime
Estimate operating time from capacity, load and duty cycle.
Estimated runtime--
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DC cable voltage drop
Estimate round-trip loss in station power wiring.
Voltage drop--
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Resistor voltage divider
Calculate unloaded or loaded divider output voltage.
Output voltage--
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Location & mapping 3 tools
Postcodes, coordinates, Maidenhead locators and WAB squares
UK postcode to Maidenhead locator
Find the approximate postcode centre, locator, coordinates, national grid reference and Google Maps position.
Maidenhead locatorEnter a postcode
The lookup runs only when you press the button.
Open in Google MapsCoordinates to Maidenhead locator
Convert WGS84 latitude and longitude into a 6-character locator.
Maidenhead locator--
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WAB square from postcode or locator
Find the 10 km Worked All Britain square from a UK postcode or Maidenhead locator.
WAB squareEnter a postcode
Choose an input type, enter the location and press the button.
Open in Google MapsRepeater input / output frequency
Apply a positive or negative repeater shift to a known frequency.
Repeater input--
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Forward & reflected power
Estimate reflected and delivered power from forward power and VSWR.
Reflected power--
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dB gain & loss chain
Add three gain or loss stages and calculate final RF power.
Final power--
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Antenna trim correction
Adjust an existing element length from its measured resonance to a target frequency.
New estimated length--
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UK repeater & gateway finder
Find nearby UK radio systems with distance and beam direction from your postcode.
Search from your postcode
Results include frequencies, modes, access information, keeper, locator and station details.
Use these calculators as practical starting points. Real installations vary with component tolerance, cable condition, connectors, temperature, antenna surroundings, terrain and measurement method. Check critical work with suitable test equipment.