Radio Frequency Fundamentals and Spectrum Concepts
The ISED Basic exam uses this domain to confirm that you can handle decibel arithmetic, convert between frequency and wavelength, and explain how Canada manages its radio spectrum. The questions are short and numerical, so unit discipline matters more than prose.
Working with decibels
Gain and loss add in dB and multiply as ratios: 3 dB is a factor of 2, 10 dB is a factor of 10, and 0 dBm is 1 mW. Useful anchors are 30 dBm = 1 W = 0 dBW and 20 dBm = 100 mW. Cascaded stages add: 20 dBm into a 10 dB amplifier followed by 3 dB of cable loss gives 27 dBm. Never add dBm values as if they were watts.
Frequency, wavelength, bandwidth
Wavelength in metres equals 300 divided by frequency in MHz, so 100 MHz is 3 m, 150 MHz is 2 m and 2450 MHz is about 12 cm. Propagation follows frequency: HF reaches beyond the horizon by ionospheric refraction, VHF and UHF are essentially line of sight, and above roughly 10 GHz rain and foliage absorption become significant. Free-space path loss grows 20 dB per decade of distance and of frequency: FSPL(dB) = 32.45 + 20log(f in MHz) + 20log(d in km).
Spectrum in Canada
ISED administers the Radiocommunication Act and publishes the Canadian Table of Frequency Allocations, which follows the ITU regional structure. Apparatus is either licensed or licence-exempt; every band carries limits on power (ERP or EIRP), out-of-band emission, frequency tolerance and, for digital systems, bandwidth or power spectral density.
Worked example
A 10 W transmitter feeds an antenna with 6 dBd gain. 10 W is 40 dBm; adding 6 dB gives 46 dBm ERP, which is about 40 W. To convert to EIRP add 2.15 dB: 48.15 dBm, or about 65 W. The lesson: ERP references a half-wave dipole, EIRP an isotropic radiator, and switching between the two always costs 2.15 dB.
Traps that cost marks
Mixing ERP and EIRP; treating peak envelope power as average power; forgetting feedline loss between transmitter and antenna; and using the wrong frequency unit in the wavelength formula.