Methodology
Each calculator documents its formula, units and assumptions. Where a physical constant has a defined exact value, that value is used directly in the calculation.
The Frequency ↔ Wavelength calculator uses the exact defined speed of light in vacuum, 299,792,458 metres per second.
The Antenna Length calculator uses established amateur-radio construction starting formulas: 468/f MHz feet for a half-wave dipole, 234/f MHz feet for a quarter-wave radiator, and 1005/f MHz feet for a full-wave loop. These are intentionally presented as starting dimensions rather than guaranteed resonant lengths. It also provides broad feed-impedance estimates and quarter-wave transformer guidance so that the user can compare the antenna with a 50 Ω, 75 Ω or custom target system impedance.
Practical engineering effects that require additional assumptions—such as cable velocity factor, antenna end effects or manufacturer-specific loss data—are kept out of generic calculators unless those assumptions are explicitly exposed to the user.
Results should be treated as engineering aids, not as substitutes for measurement, manufacturer data, applicable standards or regulatory requirements.
These tools are engineering aids. Real installations should still be checked against measurements, manufacturer data, applicable standards and regulatory requirements.
ERP / EIRP
The ERP / EIRP calculator works in logarithmic power units: transmitter power is converted to dBW, feedline and passive RF losses are subtracted in dB, and antenna gain is then added. Antenna gain entered in dBd is converted to dBi by adding 2.15 dB; gain entered in dBi is converted to dBd by subtracting 2.15 dB. The resulting EIRP is therefore always 2.15 dB higher than ERP for the same physical system.
SWR / Reflected Power
The SWR / Reflected Power calculator uses the magnitude of the reflection coefficient Γ. From SWR, |Γ| = (SWR − 1)/(SWR + 1), and the reflected-to-forward power ratio is |Γ|². In reverse mode, |Γ| is obtained from the square root of reflected power divided by forward power and SWR is then (1 + |Γ|)/(1 − |Γ|). Return loss is −20 log10(|Γ|), while mismatch loss is −10 log10(1 − |Γ|²).
Free-Space Path Loss
The Free-Space Path Loss calculator uses FSPL = 20 log10(d) + 20 log10(f) + 32.44 when distance is in kilometres and frequency is in megahertz. It can also solve the same relationship for distance. Optional received-power estimates use the Friis link-budget form in decibels.
RF Link Budget
The RF Link Budget calculator converts transmitter power to dBm, subtracts transmitter-side losses, adds transmit antenna gain to obtain EIRP, subtracts free-space path loss and any additional user-entered path loss, then adds receive antenna gain and subtracts receive-side losses. Link margin is the resulting receiver-input level minus receiver sensitivity. Reverse mode solves for the maximum FSPL that still leaves the selected required margin and then converts that allowable path loss to ideal free-space distance.
Receiver sensitivity presets and µV conversion
The RF Link Budget receiver presets are reference examples based on published receiver specifications rather than universal category averages. The calculator changes the suggested profiles according to frequency but does not assume that frequency uniquely determines modulation. Sensitivity may be entered in dBm or microvolts. For conversion, the calculator assumes RMS terminal voltage across the selected resistive reference impedance and uses P = V²/R; 75 Ω is used for the broadcast-FM reference presets and 50 Ω for communications-receiver presets.
RF Link Budget environment correction
The environment module keeps environmental loss separate from free-space path loss. Terminal clutter uses the height-gain correction in Recommendation ITU-R P.2108-1 for 30 MHz to 3 GHz, with the Recommendation's representative clutter heights of 10 m for open/rural and suburban, 15 m for urban/trees/forest and 20 m for dense urban when better local information is unavailable. Vegetation uses the mixed-forest excess-loss relationship and tabulated reference values in Recommendation ITU-R P.833-10; the low and moderate vegetation selections are explicit planning-density multipliers rather than ITU categories. Building entry uses the median horizontal-incidence form of Recommendation ITU-R P.2109-2 for traditional or thermally-efficient buildings over its stated frequency range.
Digital Audio File Size
Uncompressed PCM bitrate is sample rate multiplied by bit depth and channel count. Storage is that bitrate multiplied by duration and divided by eight to convert bits to bytes.
Audio Level Converter
The audio level converter uses 0.775 Vrms as the dBu reference and 1.000 Vrms as the dBV reference. Peak and peak-to-peak voltage equivalents assume a sine wave.
Streaming Bandwidth and Maximum Listeners
Streaming bandwidth is stream bitrate multiplied by simultaneous listeners, with optional percentage allowances for protocol/delivery overhead and operational headroom. Maximum-listener calculations reverse the relationship after reserving a chosen fraction of the connection.
Streaming Data & Storage
Encoded audio data is bitrate multiplied by time and divided by eight. Listener-transfer mode multiplies that figure by the average simultaneous audience and delivery overhead; archive mode stores one encoded copy regardless of audience size.