In Australia’s major capital cities, the main transmitter for digital TV signals requires a VHF antenna, in order to receive frequencies that are located in the VHF spectrum.
In terms of what design of outdoor antenna is available for the VHF spectrum in Australia, you are limited to two main options, either (i) a yagi antenna, or (ii) a log periodic. Note that there are also VHF phased array and omni-directional designed antennas available, however, they are very rarely used.
The Yagi-Uda antenna (“Yagi” for short) is an antenna design that is directional and consists of at least 2 parallel elements (arms), in what they call an end-fire array. They can also have other elements not used to for electrical connectivity, called reflectors and directors.
In short, amongst VHF digital TV antennas available in Australia, yagi antennas are easily recognisable by the fact that the elements are all of approximately equal length. Most commonly in Australia, they will have a minimum of 4 elements and a maximum of 18 elements.
Due to the fact the length of the elements relate inversely to the frequencies which the antenna is designed to receive signals, VHF yagi antennas in Australia are cut to receive channels 6 – 12 (Band 3). Note that when we say ‘channels’ here, we are not referring to the channels you tune in on a TV (e.g. Network 7), but rather the RF frequency channel.
Yagi antennas are designed to receive only a very small, specific range of RF channels. They work very well in a small range of frequencies. Luckily, digital TV signals in Australia are only spread over a small range of frequencies, making yagi antennas a perfect match!
Getting a little more technical, by design they often exhibit very good signal characteristics. Possibly the most important signal characteristic of an antenna is signal gain, and yagi antennas provide the very best option in this regard. In addition, the front to back ratio of a yagi antenna is also normally very good, due to the fact that the reflectors and directors block many unwanted signals. This contributes to the antenna receiving a signal with very strong signal strength as well as very high signal quality.
Log Periodic Antennas
The Log Periodic Directional Antenna (“LPDA” for short) is an antenna design that is directional and consists of elements of varying lengths. It is designed to receive a very wide range of frequencies but as a result will have low gain.
Compared to a yagi, which will have all elements the same length, LPDAs will have a large number of pairs of elements that have an equal length. You can think of this as though each pair of elements (that are the same length) are a separate antenna, and so each additional pair of elements will simply add a new separate antenna that receives a different frequency range.
Large “log” antennas can receive a very wide range of frequencies and in Australia, most log periodic antennas will receive VHF and UHF frequencies.
Unlike yagi antennas, where additional elements result in higher gain, with LPDAs, more elements result in the antenna being able to receive a wider range of signals. It will not normally result in a better quality or stronger signal.
On the technical side of things, LPDAs will have a very wide frequency range, however will lack in some key characteristics. LPDAs will have low signal gain (the most important signal characteristic of an antenna), and will also have a relatively weak front to back ratio.
The Winner Is...
In short, a yagi antenna wins hands down for VHF digital TV signals in Australia.
If you are comparing the two designs, LPDAs really only have 2 elements dedicated to grab the VHF signals you are trying to receive. Whereas yagi antennas will have a minimum of 4 elements (and anywhere up to 18 elements) dedicated to grabbing those same signals.
LPDA antennas fundamentally work in a completely different way to yagis. Adding elements to a yagi increases its directionality, or gain, while adding elements to a LPDA increases its frequency response, or bandwidth.
This points to the one reason why an inexperienced TV antenna installer may use an LPDA. It is normally able to receive both VHF and UHF frequencies.
If an inexperienced TV antenna installer doesn’t know which signal is available in a ‘fringe’ area, he or she can use a log periodic antenna to receive either one!
However, remember that in 99% of cases, the correct yagi antenna will receive a far better signal than a log periodic antenna (for both signal strength and signal quality).
Apart from design, there are a number of other important considerations you should take into account when selecting an antenna.
If you want to get a little more technical, you should read our article on TV antennas used in Sydney. This provides more background on additional technical considerations, including built-in filters.
In addition, for outdoor antennas, you should always take into account the durability of the antenna.
It is a device that will be outside for many years. It will be exposed to the often harsh Australian environment, including very hot weather, wind, rain, hail and electrical storms. Not to mention the cockatoos and other birds!
In our experience, a strong, durable antenna will last decades, whereas a flimsy antenna will normally last a few years. It is for this reason that we always recommend and install Australian made antennas only. They are manufactured by companies that have Australia (and its environment) at the front of their minds when considering design and quality control.
In recent years, there have been a flood of poorly manufactured, overseas made log periodic antennas hit the Australian TV antenna market. They are the cheapest option available to TV antenna installers (often costing as little as $15-$20) and often fail due to elements that are easily bent by birds simply landing on them once. They are yet to stand the test of time to see if they would last 25 years or more and we have replaced many (“new” ones) in recent years.
Having been established in 1981, the team at Nu Life TV have over 40 years experience in installing TV antennas in Australia. We are Australia’s longest serving TV antenna company and over the years, we have seen what works and what doesn’t work.
Our advice is, don’t fall for the hype of a cheap international log periodic. Stick to the tried and tested Australian made yagi antenna for VHF signals in Australia.