Why are digital antennas smaller?
It’s not to save on manufacturing costs, it’s not by regulation and definitely not by coincidence.
It’s to make them receive a stronger signal. That’s right, these smaller antennas pick up a stronger signal.
Still don’t believe it?
There’s a science behind it.
Every channel is transmitted from the tower using a different frequency.
For example, in Perth currently digital channels run on frequencies 177.5mhz – 226.500 mhz
The length of the wave differs for each frequency being used, remember that.
Let’s calculate the wavelengths, and half wavelengths for the frequencies most common channels received from a TV antenna in Perth
Each arm of a TV antenna has a different length. The length of each arm must be a specific length in order to pick up the strongest signal on each different channel.
For most TV antennas, 1/2 the wavelength of each arm is used
For example, the now obsolete analog channel 2 (ABC) ran on a low frequency and had a extremely long wavelength. In comparison, the Digital TV frequency for ABC has a very small wavelength
Lower Frequency = Larger Wavelength = Larger antenna arms
Higher Frequency = Shorter Wavelength = Smaller antenna arms.
(Antenna Arm Diameter)
|ABC Analog (obsolete)||64.25 mhz||2407 mm|
|Seven Digital||177.5 mhz||844 mm|
|SBS Digital||184.5 mhz||812 mm|
|Nine Digital||191.5 mhz||782 mm|
|Ten Digital||219.5 mhz||682 mm|
|ABC Digital||226.5 mhz||662 mm|
Analog TV frequencies started as low as 64.25mhz, where ABC was located, requiring arm diameters as long as 2407mm
Digital TV frequencies have the lowest frequency on 177.5mhz, where Channel 7 is located, requiring arm diameters as short as 844mm.
With digital frequencies being higher, the larger elements of analog antennas are no longer needed,
A smaller “digital antenna” can then outperform a larger “analog antenna” because it’s arm lenghts are specifically tuned to the frequencies it needs to receive and at the same time reject any out of band interference.