Lualualei VLF transmitter facts for kids

Quick facts for kids VLF transmitter Lualualei, Mast 1
General information
Status	Complete
Type	Mast radiator insulated against ground
Location	Lualualei, Hawaii, United States
Coordinates	21°25′13.38″N 158°09′14.35″W / 21.4203833°N 158.1539861°W / 21.4203833; -158.1539861
Completed	1972
Height	458.11 m (1,503.0 ft)
Design and construction
Main contractor	US Navy

The VLF transmitter Lualualei is a special radio station in Lualualei, Hawaii. It belongs to the United States Navy. Its main job is to send messages to submarines that are deep underwater. It uses a very special type of radio wave called very low frequency (VLF) to do this. These waves can travel through water better than regular radio waves.

What is the Lualualei VLF Transmitter?

The Lualualei VLF transmitter uses the callsign NPM. This is like its special name when it sends out radio signals. It broadcasts on two different radio frequencies: 21.4 kHz and 23.4 kHz. A kilohertz (kHz) is a way to measure how fast radio waves wiggle.

This station uses a huge antenna system. It has two tall masts, which are like giant poles. Each mast is about 458 meters (1,503 feet) tall. That's taller than many skyscrapers! These masts were built in 1972.

How Tall Are the Masts?

When they were built, these masts were the tallest structures in the Western Hemisphere used for military purposes. They are also the tallest towers in the Western Hemisphere that send out long radio waves. After the Warsaw Radio Mast fell down, these masts became some of the tallest structures in the world that are electrically insulated from the ground. This means they are designed so electricity doesn't flow into the earth directly from the mast itself.

How Do the Antennas Work?

Both of these giant masts are what we call "umbrella antennas." Imagine a giant umbrella, but instead of fabric, it has many wires spreading out from the top of the mast. These wires help the antenna send out radio signals very powerfully.

The radio signal travels to the masts through a special overhead cable. This cable is attached to the top of the mast on one side. On the other side, it connects to a smaller mast near a building called the "helix building." The small mast is connected to the ground, but the cable is attached to it with a special part called an insulator. This insulator makes sure the electricity stays in the cable and doesn't go into the ground too early. This whole setup helps the VLF transmitter send its important messages to submarines far away.