Where is Leaky Feeder Cable Useful?

Where is Leaky Feeder Cable Useful?

In amateur radio we wish to have the feeder coaxial cable take the radiofrequency signals from the radio direct to the antenna without any radiation on the way. If it does radiate along its length, we have RF inside the room. RF inside the room is picked up by all metallic objects and you can get ‘RF bites’ when you touch them. Needless to say the RF interference it causes in sensitive equipment inside the room. So when is it that you actually need a leaky feeder cable which itself acts as an antenna? A leaky feeder, otherwise known as a radiating cable, is used in underground mining and other tunnel environments to provide a communication system. There are gaps in outer conductors to allow radio signals to leak out and into the cable in leaky feeders.

The signal loss naturally would mean the addition of booster amplifiers at intervals of 350 to 500 meters. The leaked signals are useful for communicating with portable radios used by persons in the tunnel or mine. Frequencies in the VHF and UHF range below 1 GHz are useful, while the losses would be higher above that cutoff level. Such a system is needed because the surrounding rocks would not otherwise permit line-of-sight communication on these bands. These systems are also employed in underground rail systems. It can also enable high speed mobile data coverage for passengers using underground rail system. Similar systems are also useful in aircrafts to provide on-board cellular and WiFi coverage. Leaky feeders could even be used in hotels, warehouses and other industrial buildings to provide WiFi coverage.

My sincere thanks to VU3ULL for introducing this topic in a discussion on VU2IAC Thrissur Repeater Group! He had also mentioned that these could be used along with Bluetooth Beacons to get location in DMR despatchers.