Radio Frequencies and Microwaves - Magnetic and Electrical Fields 1971 https://ia800306.us.archive.org/4/items/nasa_techdoc_19720063229/19720063229.pdf As all stations radiate incoherently, the "radio ^background" is then the   result of accumulated radiation. In the environs of long-wave and medium-wave   stations, as well as television stations, there is daily periodicity of   intensity variations, as these stations usually discontinue operations from   approximately 1 a.m. to 6 a.m. Short-wave stations, transmitting all over   the world, operate practically aroimd the clock.  Local artificial EMF zones are created around generators and affect only   the staff directly attending these generators in industrial plants, radio,   and television stations and medical institutions. According to the evalua-   tions of Soviet hygienists, EMF intensities at working sites are:  a) EMF (50 cps): in electrotransmission lines, transformers, etc., field   intensities can reach hundreds of V/m, and in open distributors they can   reach thousands of V/m.  b) High-frequency EMF (hundreds of kc) : intensities close to the   generators (for hardening metals, drying wood pulp, etc.) can reach thousands   of V/m and dozens of A/m with respect to the magnetic component.  c) Ultra-high frequency EMF (from several to tens of Mc) : intensities   reach hundreds of V/m.  d) Superhigh frequency EMF (from hundreds to thousands of Mc) : can /6