Site of the DCF77 transmitter is the transmitting radio station Mainflingen (coordinates: 50°01' north, 09°00’ east) approx. 25 km south-eastern of Frankfurt/Main.
The earthing network on the site of the transmitting radio station as well as the high ground-water level due to the site’s position in the lowlands of the river Main cause a high ground conductivity and thus favourable radiation conditions. The control signal is not transmitted from Braunschweig via lines, as is often assumed, but is generated in situ with the aid of a control device designed by PTB and monitored from Braunschweig. After the DCF77 signal generated by the PTB facilities has been conducted to Media Broadcast GmbH, this company is responsible for emitting it via the transmitting and antenna facility operated by it.