Selecting the Right Antenna
This guide has been designed to provide a very easy to understand introduction to improving signal on Australian networks. Before we begin it's important to understand that you will need three pieces of equipment to improve your mobile signal:
So an antenna is the obvious one. But it's often overlooked that your mobile phone or wireless broadband modem is connected to an antenna just like your TV is, and just like your TV, it's antenna works best when installed on the outside of your car or house, and as high as possible. This means you'll need some cable to cover the distance from where you want to put the antenna, to where you want to use your phone or modem.
You'll then need something to connect your cable into your phone or modem. Modems are very easy - all good quality modems have an external antenna port, meaning all you need is a small adapter cable called a Patch Lead to go from the big connector on the cable to the tiny connector on your modem. Many phones also sport an external antenna port, most notably Telstra, Samsung, and Motorola brand phones. If your phone doesn't have an antenna port, don't worry you'll just need to use a Cradle.
If you don't like the idea of having to constantly tether your phone to a patch lead or cradle, that's easy - you'll just need to connect your antenna to a Smart Repeater, which will amplify and broadcast your antenna's signal throughout your house at full strength, giving your mobile phones a full 5 bars.
Let's Get Started...
There's four main factors that reduce mobile coverage:
Distance from the cell tower
Dense vegetation & buildings
It's no surprise mobile signal is reduced by distance (due to the Inverse-Square Law) from the cell tower, causing a gradual weakening of signal. In flat terrain, most cell towers have a usable range of about 40km before you'll need to use an external antenna. With a good quality external antenna it's possible to receive signal as far as 120km!
Because of the diffracting nature of radio waves (bending over hills, around objects) it’s important to understand that being able to see a cell tower is not the ‘be all and end all’ of obtaining signal - if you've travelled through a hilly area you'll no doubt have noticed you still have mobile reception despite being in a small dip or behind a rise in terrain. Large or sudden changes in terrain will however significantly impact phone coverage – in this type of scenario the important success factor is gaining height by raising an antenna into the air.
Dense sections of trees are notorious for diffusing signal. Typically one or two trees on their own don't tend to impact signal strengths too greatly, however it's analogous to 'death by a thousand cuts' where each tree absorbs or deflects a small amount of signal. The best way to mitigate this phenomenon is again by increasing height to minimise the path length that signal must pass through the offending vegetation.
Mobile signal is reduced when passing through buildings, trees, water, and even the air we breathe. The worst offenders are thick and conductive materials such as concrete, metals and foil-based insulation – this is often why signal can be weak indoors despite a strong signal outside.
For a comprehensive look at all the factors involved, have a read through our Poor Coverage Explained guide.
Step 1 - What network am I on?
On the surface this seems like a simple question to answer and for some networks, like Telstra, it is. However what we really want to determine is what frequency the network operates on in your area. While there are countless mobile network operators, there are only three mobile networks operating in Australia - Telstra, Optus, and Vodafone. Please use our Coverage Maps to determine what frequency your network is running on. For a brief guide expand the table below.
Step 2 - Where am I?
Different antennas are designed for different situations. You'll need to think about where you're trying to improve service - the house? the car? Are you in one location or moving about? Rather than talking about antenna types and gains, this guide will work through the best antennas for houses, vehicles, and marine vessels.
The House or Office
The best place to start is often by performing a quick self check. Walk around the house – is there a particular spot where signal is good? Walk outside the house or on to the street – does signal improve? Climbing up on your roof can give you an idea whether height is an important factor in improving signal. The next important thing you can do is work out where the nearest Telstra tower is, and how many are in the area. You can find this out by following our Locating a Phone Tower guide. If you couldn't work it out you can book in for a Detailed Site Assessment where we can look after everything for you.
If you're on the move or don't have the room to mount a cumbersome roof antenna, an indoor antenna is a convenient way to improve mobile phone service or wireless broadband speed. While the much smaller dBi gain reduces strength, it instead allows these antennas to receive from many directions - no need to fiddle about to find the optimal direction - perfect if you're moving around or don't know where the best cell tower is.
If you've noticed your signal strength is usually stronger next to a window or doorway then this is often the best place to put an antenna. One of our most popular models is our 12dBi window mount antenna - it's adhesive stick on mounting makes installation a breeze.
Most issues with slow wireless broadband or bad phone reception are solved with a roof mounted antenna. If you've located your nearest cell tower, the next step is a breeze.
There are two main types of roof antennas - omnidirectional (collinear) antennas, and directional (yagi) antennas. Omnidirectional antennas are designed for areas around town or in the suburbs where there are often several cell towers within range. This antenna leaves your mobile to decide which tower offers the best signal. However you'll notice as they spread their power over a 360° range, they do not receive as strongly as their yagi counterparts.
Directional, or, Yagi antennas are the much more popular choice as their high power provides the strongest increase of all antenna types. The trade-off here is that they require aligning in the direction of the cell tower - the higher the dBi gain, the more precise you will have to be. In deciding between yagi models, the wider angle of the 12-14dBi antennas make them more suitable for hilly areas, with the 15-16dBi antennas more suited to very long range connections with less hills in the way.
There are typically 3 yagi antennas that we recommend for different areas depending on their terrain type and distance.
- 12dBi LPDA Yagi: Short Distance (1-15km) or Nearby Hills (1-5km)
- 14dBi or 15dBi Yagi: Moderate Distance (15-30km)
- 16dBi Yagi: Long Distance (30-70km) or Flat Areas (hills > 15km away)
Thankfully choosing antenna for your vehicle usually isn't too complex. You'll notice that all car antennas receive from all directions, and follow the same principles as your UHF aerial (if you have one).
The choice of antenna depends on the area you're travelling through. While a higher gain means a stronger signal, when you increase an antennas gain (ie it's dBi), the angle it can receive from is reduced - this means that high gain antennas are more suited to flatter areas, and moderate gain antennas (such as a 5-6dBi) better suited to hilly areas.
One of the most critical decisions you can make is to use a high quality Australian made antennas - such as the RFI and ZCG Scalar brands. These durable antennas have been specifically designed for the tough Australian environment and have a much more sophisticated internal design, allowing most models to operate on multiple mobile networks.
Built up areas often have several cells within a few kilometres and are usually mounted on tall monopoles or on top of hills. The antenna of choice for many fleet and commercial vehicles is the 5dB RFI CD1250 or the 6.5dBi RFI CD2195.
General Highway & Travelling
If you're after a versatile antenna capable of functioning in a range of different terrains, the 6.5dBi RFI CDQ2195 and 7.5dBi RFI CDQ2197 are the antennas of choice for all Australian networks.
Outback QLD & WA
For flat outback areas the clear choice is the ultra high gain 9dBi RFI CDQ2199. We often hear of customers purchasing falsely advertised 9dBi antennas - a 7dBi antenna should measure about 1.1m and a 9dBi antenna should measure about 2m in length.
Marine antennas are typically high gain omnidirectional antennas (6-9dBi) to allow maximum off shore range no matter which direction your vessel faces. Selecting an appropriate antenna depends on the type of vessel you have, and how far off shore you plan on going. As a simple rule of thumb, the higher the antenna gain the further off shore you can go. 8 or 9dBi marine antennas can easily extend your range past 120km off the coast. However because higher gain antennas have a smaller angle in which they can receive signal, smaller vessels that sway side-to-side may be better off with a slightly lower gain (such as a 7.5dBi) antenna to compensate for the motion.
In practice this is generally not an issue for most vessels - the receiving angle is a 'half power' measure, meaning that if your boat was to swing past the quoted angle, the received gain would be 3dB less (half the power in Watts), the same as a lower gain antenna anyway.
Here are some we recommend:
- ZCG 8.1dBi Deck Mount Antenna
- ZCG 8.1dBi Mast Mount Antenna
The first step in understanding antenna gain is that your phone or modem's internal antenna gain is typically -15 to 0dBi. As such any good quality external antenna usually provides immediate benefit regardless of stated gain. The key here is quality which is typically measured by electrical efficiency, pattern stability, and VSWR - gain on the other hand is all about how the antenna focuses the radiated power.
You might be wondering why would anyone buy a 6dBi antenna when they can buy a 9dBi instead. While it is true that a 9dBi has a higher gain, a higher gain does not always result in better performance. Different antenna sizes and type have differing 3 dimensional patterns in which they receive signal. This is referred to as an antenna ‘radiation pattern’, and is often measured in terms of vertical and horizontal beamwidth.
Beamwidth refers to the angle in which an antenna receives signal, and is measured in degrees from the horizontal axis. Let's suggest that in a perfect world all antennas receive the same amount of signal from the surrounding atmosphere in the shape of a doughnut, where width represents physical distance, and height represents physical height. Given that you've only got a certain amount of dough (signal) to make the doughnut with, you can either make your doughnut tall and skinny, or flat and wide (or perhaps somewhere in between). In terms of beamwidth, a tall doughnut has a larger vertical beamwidth, and a flat doughnut a small vertical beamwidth.
Different Types of Antenna
Aside from differing in gain, antennas also differ in their type of build. Each different build offers a different set of advantages and disadvantages.
Omnidirectional Antennas (Ground Independent)
These are the most common type of mobile phone/UHF/CB antenna and have a 360-degree horizontal beamwidth, meaning they work in all directions. This type of antenna does not require a ground plane to function, and hence it can be mounted with a small bracket on just about any surface and in any location. Best performance is achieved by mounting the antenna as high as possible - to eliminate as much signal interference as possible.
Magnetic Base Antennas (Ground Dependent)
A type of omnidirectional antenna that must be mounted onto a metal surface. Magnetic Base, or, Ground Dependent antennas are half the size of a ground independent designs by using the metal surface that they are connected to as the other half of the antenna. This means that the size, shape, and surface area of the metal object are very important in achieving the best possible result. This ground plane follows the same principles as the antenna - a larger surface allows for a larger fraction of the wavelength. Ideally a surface with a diameter greater than one wavelength (about 35cm for Telstra Next-G 850MHz) will perform best, smaller surfaces down to 9cm will produce acceptable results (quarter wave).
Magnetic base antennas also achieve a more compact design by incorporating one or more loading coils, which help to maintain resonance, improve the radiation pattern, and most of all make the antenna more flexible - very important for vehicles with low clearance.
Magnetic antennas are ideal for vehicles, but also make great indoor household antennas when mounted on filing cabinets and windowsills, and their compact design makes for an ideal travelling companion. While designed for metal surfaces, this type of antenna can be used on any other surface but will produce a gain 3dB less than what is stated - for example, a 7dBi magnetic antenna on a wood surface produces a 4dBi gain.
That bizarre looking TV antenna on your roof is the most common example of a yagi antenna. With a much more powerful gain, it differs from the antennas discussed so far in the sense that it is a directional antenna. This means that to function effectively, it has to be pointed in the direction of the mobile phone tower. Yagi antennas trade their ability to work in all directions (omnidirectional), for an increased gain. This is achieved by putting an array of smaller 'director elements' in front of the actual connected element. These director elements receive incoming signal and re-radiate the signal, until it reaches the driven element (the one connected to the cable). Behind the driven element there is a slightly larger element known as a reflector, which simply does as its name suggests - reflects signal back to the driven element.
By increasing the number of director elements and length of the Yagi we reduce the horizontal and vertical beamwidth - resulting in an increased gain. For a 3dB (twice the power) increase in gain, we have to double the length of our Yagi. For these reasons often a Yagi will max out at 16dBi (on 850MHz) before becoming impractically long.
Grid Parabolic Antennas
A Yagi increases it's gain by increasing it's length. Grid Parabolic antennas however increase their gain by increasing their width. This is sometimes preferable as they do not require stabilising brackets or cross bars. This type of antenna works in the same manner as a satellite dish - signal is reflected off the dish/grid and onto the small receiving element placed above the centre of the grid or dish.