ISED Basic cheat sheet

Wavelength: λ (m) = 300 / f (MHz). A 150 MHz signal has λ = 2 m; a 27 MHz signal has λ ≈ 11.1 m.

Free-space path loss: FSPL (dB) = 32.45 + 20log10(f in MHz) + 20log10(d in km). Loss rises 6 dB per doubling of distance or frequency.

Decibels: dB = 10log10(P2/P1) for power, 20log10(V2/V1) for voltage. +3 dB ≈ double power, +10 dB = ten times power, −3 dB ≈ half power.

dBm is power relative to 1 mW: 0 dBm = 1 mW, 30 dBm = 1 W, 20 dBm = 100 mW, 10 dBm = 10 mW.

EIRP (dBm) = transmitter power (dBm) + antenna gain (dBi) − feedline loss (dB). ERP = EIRP − 2.15 dB.

Frequency bands: LF 30–300 kHz, MF 300 kHz–3 MHz, HF 3–30 MHz, VHF 30–300 MHz, UHF 300 MHz–3 GHz, SHF 3–30 GHz.

Modulation: AM varies carrier amplitude, FM varies carrier frequency, and digital schemes (FSK, PSK, QAM) map bits onto amplitude, phase, or both.

Occupied bandwidth is the width containing 99% of mean radiated power; necessary bandwidth is the minimum width needed for the emission class.

Polarization describes the orientation of the electric field; horizontal and vertical are linear, and circular polarization rotates as the wave propagates.

Certification is required before sale, lease, offer for sale, or import of radiocommunication apparatus; the certificate holder is responsible for compliance of each unit.

Technical standards prescribe limits on frequency stability, output power, occupied bandwidth, spurious emissions, and unwanted emissions for each equipment class.

A test report must be produced by an accredited or recognized test laboratory and reference the applicable standard, test methods, and measured values.

Certification marks and labels must appear on the device as specified, and the certificate number must be traceable to the certified product model.

Changes to hardware, firmware affecting RF parameters, or antennas may require a new or amended certificate; minor non-RF changes follow the variation procedure.

Foreign test data may be accepted where a mutual recognition arrangement or designated laboratory status applies; otherwise domestic testing is required.

Equipment categories with defined exemptions (for example very low-power or receive-only devices) still must meet applicable emission limits.

Certificate records include applicant identity, equipment model, frequency range, RF power, emission designator, and standard version applied.

EMC has two aspects: emissions (the device must not disturb others) and immunity (the device must tolerate expected disturbance).

Conducted emissions travel on cables and power leads, typically 150 kHz–30 MHz; radiated emissions are measured through the air, typically 30 MHz–1 GHz and above.

Common-mode currents on cables are a frequent cause of radiated emissions; ferrite chokes, shielded cable, and proper bonding reduce them.

Co-channel interference occurs on the same frequency; adjacent-channel interference comes from nearby frequencies and is reduced by filtering and tighter spectral occupancy.

Intermodulation products at 2f1 − f2 and 2f2 − f1 are generated in nonlinear stages; improving linearity and filtering reduces them.

Harmonics are integer multiples of the transmitter fundamental and must be suppressed by low-pass or band-pass filtering to meet spurious limits.

Shielding effectiveness depends on material, seam and aperture size; apertures larger than about one-twentieth wavelength leak significantly.

Grounding and bonding should create a low-impedance reference; a single-point ground at low frequency and multiple-point bonding at RF reduce loops.

Antenna gain (dBi) compares to an isotropic radiator; dBd compares to a half-wave dipole, and dBi = dBd + 2.15.

Half-wave dipole length ≈ 143 / f (MHz) metres, shortened by a velocity factor of about 0.95 in practice.

VSWR relates to reflection coefficient Γ: VSWR = (1 + |Γ|)/(1 − |Γ|). VSWR 1.5:1 gives about 4% reflected power; 2:1 gives about 11%.

Return loss (dB) = −20log10|Γ|; return loss 14 dB corresponds to VSWR ≈ 1.5:1.

Feedline loss adds directly in dB and reduces both transmit power and receive sensitivity; use the shortest, lowest-loss cable and quality connectors.

Antenna height and clearance matter: Fresnel zone clearance and height above terrain affect path loss and coverage more than raw gain in many cases.

Transmitter duty cycle and thermal design determine continuous versus intermittent ratings; operating beyond rated power or duty cycle degrades spectral purity.

Installation must provide mechanical support, lightning protection, and a bonded ground; mast, guy wires, and connectors must withstand wind and ice loading.

Use only antennas and power settings permitted by the certification; changing antenna type or gain may invalidate compliance with EIRP and spurious limits.

A spectrum analyzer displays amplitude versus frequency; resolution bandwidth must be narrow enough to resolve the emission and set consistently with the standard.

Detector choice matters: peak, quasi-peak, and average detectors give different results; quasi-peak is used for many disturbance measurements.

A reference level and attenuator must be set so signals do not overload the front end; verify with a known signal before measuring low-level spurious emissions.

Power is measured with a calibrated power meter or a spectrum analyzer with correct resolution bandwidth; average power and peak envelope power differ for modulated signals.

VSWR and return loss are measured with a directional coupler, bridge, or vector network analyzer after calibration at the measurement plane.

Field strength is measured in dBµV/m with a calibrated antenna and antenna factor: E (dBµV/m) = V (dBµV) + AF (dB/m).

Measurement uncertainty must be calculated and reported; compliance is judged against limits with the uncertainty applied per the standard's rules.

Test setup must control ambient noise, cable loss, and ground plane conditions; a test range must be verified before formal measurements.

Calibration certificates for all instruments and antennas must be current and traceable to national standards.

RF exposure limits are frequency dependent and expressed as power density (W/m²) or specific absorption rate; keep antennas away from occupied areas and calculate exclusion zones.

Never work on an antenna or feedline while the transmitter is energized; lock out and tag out, and discharge stored energy before servicing.

Antenna installations require attention to fall protection, tower climbing qualifications, and separation from power lines.

Operators must hold the applicable licence or operate under an exemption, and must comply with frequency, power, and emission designator conditions.

Records to retain include certificates, test reports, calibration records, and installation as-built information for the retention period required.

Interference complaints must be investigated and documented; operators should cooperate with the regulator and may be required to reduce power or cease operation.

Only qualified personnel may modify certified equipment; unauthorized modification can void certification and create liability.

Emergency procedures include disconnecting power, isolating feedlines, and reporting incidents to the appropriate authority.