Due to a lack of financial resources, we unfortunately have to suspend the import of any new radio frequency and mobile phone-related articles as of now (November 27, 2017). We apologize for this inconvenience and will keep you informed.

Because we received a large number of inquiries, we set up a bank account to accept donations. With their aid, we hope to resume, at least partly, the import of newly published articles to the RF archive of the EMF-Portal. Any contribution is greatly appreciated. Thank you for your kind support!

DONATION ACCOUNT: Uniklinik RWTH Aachen, IBAN: DE27 3905 0000 0013 0040 15, BIC: AACSDE33, Reference: GB-FM/380454/Arbm


Natural intermediate frequency fields

In our natural environment electromagnetic fields with intermediate frequencies are generated mainly in association with the so-called sferics. Sferics are broadband electromagnetic impulses that occur in the Earth's atmosphere as a result of natural lightning discharges. Tornados can also be a source of sferics. Sferics may extend from a few kHz to several tens of kHz (3-100 kHz).
A cloud to cloud lightning
photo: André Karwath aka Aka, license: CC BY-SA 2.5, via Wikimedia Commons