Hi there people! I think most of this blog readers are familiar with half-wave antenna such as the 2 meter dipole I’ve built as a side project (with height about 1 meter by itself).
But do you know the height of the tallest and biggest half-wave antenna ever built in the world? is it 30 meters? 50 meters? 100 meters? Nope.. the answer is 646.38 m or 2,120.67 feet high when measured from its base on the ground.
Unlike other ordinary radio tower which is build to ensure you can put the antenna at the highest point, the Warsaw radio mast acts as a half-wave antenna itself!
It height 646.38 meter is the exact length of the frequency it was transmitting which is 225kHz, most probably using this formula
half-wavelength = 300/freq * 0.5 * velocity factor
= 300/0.225 * 0.5 * 0.97
= 646 meter.
As comparison, my homebrew half-wave antenna is only 0.996 meter in length, and is drastically dwarf by the Warsaw radio mast radiator.
Completed in 1974, the Warsaw radio mast transmit public broadcast radio station using 2 megawatts on 225kHz frequency. It was also the tallest structure in the world (recorded on Guinness Book of Records) until it finally collapse on 1991 due to maintenance crew failure.
Despite its collapse and inoperability for more than a decade. The Warsaw radio mast still remained the tallest/biggest (and the only longwave LF ) half-wave antenna ever build in the world,
Impressive isn’t it? Take a look at the antenna site in Wikimapia.
Read more about Warsaw Radio Mast in Wikipedia.