A television transmitter is an electronic device used for terrestrial (over-the-air) television broadcasting. To transmit video and audio signals, a TV transmitter radiates radio waves which are received by television receivers. Radio waves travel by line of sight, they are limited by the horizon and reception distances are typically 40 to 60 miles depending on the height of transmitter station.
Bilsdale TV transmitter
On the 10th of August 2021, a blaze at the Bilsdale television transmitter disrupted tv and radio signals across North Yorkshire, Teesside and parts of County Durham. Over a million people have been affected and remain without service indefinitely after the transmitter fire. The operator stated that it will find a temporary solution but was not able to say when services would be restored. [1]
Figure 1: Bilsdale TV transmitter before the fire. [1]
Other Factors That Can Affect TV signals
Effective transmission is dependent on both the strength of the signal received directly from the transmitter and the strength of any interference signals from other sources. Wind farms and buildings can interfere with the signal.
There are two ways that buildings can cause interference to television reception:
- Obstruction: this is caused by the building physically blocking the transmitted television signal, reducing the strength of the carrier signal in the shadow of the building;
- Reflection: buildings walls can reflect the signal creating a ‘multipath interference’ whereby the signal is received multiple times by an aerial at different times.
There are three ways that wind farms can cause interference to terrestrial television reception:
- Obstruction: the wind turbine’s physical structure blocks/weakens the transmitted signal, reducing the strength of the coverage in the shadow zone. Losses in strength due to this mechanism are called ‘diffraction losses’;
- Signal chopped: the wind turbine blades intermittently ‘chop’ through the direct coverage path, causing fluctuations in received power.
- Reflection: the signal is reflected by the wind turbine’s physical structure.
About Pager Power
Pager Power undertakes technical assessments for developers of renewable energy projects and tall structures including TV transmitter interference assessments. For more information about what we do, please get in touch.
References
- Bilsdale transmitter fire: TV and radio for 1m off air indefinitely, Francesca Williams & Chris Robinson, date: 12/08/2021, last accessed: 16/08/2021
[1] Colin Grice (December 2004) from WikiCommmons. Last accessed on 16 Aug 2021. Available at: https://commons.wikimedia.org/wiki/File:High_Ewecote_and_Bilsdale_TV_mast_-_geograph.org.uk_-_95085.jpg
