Inspec keywords: sunspots; ionospheric electromagnetic wave propagation; HF radio propagation; field strength measurement; frequency allocation; ionospheric techniques

Other keywords: field strength threshold; remotely controlled UK measurement system; high frequency spectral occupancy; ionosphere; ITU; solstices; week; frequency; frequency allocation; mathematical modelling; research; extended UK models; HF; measurement bandwidth; moving average sunspot number

Subjects: Voltage measurement; Ionospheric electromagnetic wave propagation; Radiowave propagation; Measurement of basic electric and magnetic variables