<a href="https://en.wikipedia.org/wiki/Transmission_line" class="extiw" title="en:Transmission line">Transmission line</a> emerging from the transmitter building  of <a href="https://en.wikipedia.org/wiki/Sendeanlage_Bisamberg" class="extiw" title="en:Sendeanlage Bisamberg">Sendeanlage Bisamberg</a>, a medium wave broadcasting station in Bisamberg near Vienna, Austria.  It feeds radio power to the south antenna mast.  This type of transmission line is called a "cage line".  It consists of a small circular bundle of parallel wires carrying the RF current, surrounded by a larger circle of grounded wires, which function as a "shield" to prevent the power from radiating off the inner wires as radio waves.  It functions similarly to a large version of a <a href="https://en.wikipedia.org/wiki/coaxial_cable" class="extiw" title="en:coaxial cable">coaxial cable</a>.  The Bisamberg transmission facility was shut down in 2010.
Klaus Schaedler
CC BY 2.5
<span class="int-own-work" lang="en">Own work</span>