Many old antennas will pick up digital television signals. But if you want the best reception, it helps to know a little about how antennas work.

The Basics

Television signals are broadcast on electromagnetic waves. X-rays, microwaves, visible light, and radio waves are all types of electromagnetic radiation. The difference between these types of radiation depends on their frequencies. “Frequency” just means how many waves happen in one second.

Television signals use the radio wave portion of the electromagnetic spectrum, which means that they have a relatively low frequency compared to things like an x-rays or visible light. The lower a frequency is, the longer each wave is. An x-ray has a wavelength of only a few billionths of a meter, but a television signal can have a wavelength several feet long.

Different length antennas resonate to different radio frequencies, sort of like how different lengths of string on a musical instrument resonate to different frequencies of sound. An antenna that is half the wavelength of a TV signal will resonate well to that frequency, and will get the best reception on the associated channel.

TV is broadcast on very high frequency channels (VHF) and ultra high frequency channels (UHF). UHF waves are shorter and VHF waves are longer. That’s why the best antennas for VHF stations (channels 1-12) are like long “rabbit ears,” and antennas for UHF stations (channels 13 and up) can be much smaller and still catch the shorter waves. After the switch to DTV, most channels will be broadcast on UHF frequencies, so a smaller UHF antenna, or a combination UHF/VHF antenna will probably work the best for picking up digital television.

Check out this video from Twin Cities Public Television’s Make: TV for instructions on building your own high-quality digital antenna!