How to Choose an External 4G or 5G Mobile Broadband Antenna

Most of us are lucky enough to live within reach of a fairly strong UK mobile broadband (3G, 4G or 5G) network signal but that isn’t true everywhere, particularly in some remote rural areas. Sometimes the best way to receive a stronger signal is to try installing your own external antenna, but knowing what to get can be tricky.

Before we get started it’s important to clarify that this article is primarily intended for people who can’t access a good fixed line broadband ISP connection but may still be almost within reach of a viable mobile broadband alternative, albeit often struggling to get a good or stable signal from any of the operators. In this case you may benefit from an external antenna.

Obviously if you can already get a fast fixed line broadband ISP and just want a better indoor mobile signal then many of the operators already offer Femtocell style devices, which essentially plug into your home broadband connection (speeds of 0.5Mbps or 2Mbps+ are usually required) and use that to boost a localised mobile signal for your Smartphone.

Examples of Femtocell devices are Vodafone’s Sure Signal router, Three UK’s Home Signal , O2’s Boostbox or EE’s Signal Box device. Failing that some Smartphones and Apps from mobile network operators also support making calls on your allowance via home WiFi (some mobiles also have a more direct ‘WiFi Calling’ feature that does this without an app).

Let’s talk external antennas

The actual process of installing an external antenna is usually just a case of screwing one to the highest and most stable location possible outside of your house (e.g. a solid brick wall near your roof), pointing it in the right direction and then drilling the cable through into the house (making sure to avoid electrical cables, water pipes and sealing up afterwards etc.). Plenty of professional installers can do this for you too (often for sub-£100).

However as anybody who has ever tried to improve their mobile signal will probably attest, finding the right kit for the job isn’t simple and the variable nature of the radio spectrum – passing through different environments as it does – can result in all sorts of quirky outcomes. Sometimes the most logical solution doesn’t always turn out to be the right one for your specific location or needs.

Nevertheless our aim here is to provide some general guidance, but remember that sometimes it’s necessary to test a few different approaches before you decide upon the best one. In addition, we aren’t going to dare delve into the more industrial setups (e.g. personal mast construction or WiFi relays) as those are a bit too complex for most people, but if you’re surrounded by tall trees then sometimes it’s necessary to get radical.

Often it’s possible to buy a pole mounting and then fix your antenna on top of that (i.e. raised higher above your house) but just be sure that what you install is stable and won’t damage the house. Likewise in some areas a tall pole may breach planning rules, so always check with the local authority first.

Omni-directional or directional antenna

The first decision is whether or not to go with a directional or omni-directional antenna. A directional antenna will focus its higher gain (reception) in one direction, although it also becomes weaker in the other directions. By comparison omni antennas try to attract similar reception from all directions, albeit for a lower overall gain.

On the surface you may think you know the answer to this one but it’s not always so simple. If you know where the nearest mast or base station for your operator is, particularly if you have LOS or Line-of-Sight (nothing in the way), then going directional might be the best choice (often true in rural areas). However a directional antenna can run into problems, such as if the station is congested or goes out of service (can occur during upgrades).

On the flip side an omni may result in better reliability because it’s looking at a wider area, although it can also attract more interference and may not deliver the same sort of performance as a well positioned directional. Generally if you’re not entirely sure where the mast is, or you live in an urban or suburban area, then an omni is probably the better choice. In fact start with an omni first anyway, it’s just easier.

Now if you’re really feeling adventurous then you could install two antennas of different types but in order to make that work you’d have to connect them both to a MIMO configured router (two ports), such as the Huawei B618. Likewise you can also buy some MIMO antennas that have two outputs (MIMO 2×2) for related routers with two inputs. Just remember that this kind of kit tends to be more expensive and adds to the hassle of setup.

Generally it’s best to try with one antenna first and don’t bother buying a MIMO router with two external antenna ports if you’re only going to use an antenna with a single output, although if you do try installing two antennas then make sure to space them apart a bit.

At this point we should touch on polarisation. Mobile signals tend to be linearly polarised (they vibrate vertically, horizontally or a bit of both) and ideally the aim is to match the polarisation of your antenna to that of the signal (trial and error – helps if you can rotate the antenna). A quick solution to this is to go with a cross-polarised antenna, these usually have two outputs (good for MIMO routers), which can latch on to the signal regardless of its polarisation.

We’d also suggest keeping the cable between your antenna and router as short as possible in order to limit interference. Generally 5 metres or less should be fine, although some people have used more without problems but your mileage may vary (more cable usually equals greater signal loss). However, there are other factors that you need to consider too, so let’s move on.

What do the gain (dB / dBi) figures on an antenna mean?

The power of an antenna is measured by its “gain,” which is usually reflected in figures for either dBi (decibels relative to an isotropic radiator) or just dB (decibels relative to a dipole radiator – technically dBd but marketing folk often just use dB, which is confusing). The gain is essentially a relative measure of the antenna’s ability to direct (concentrate) radio frequency energy in a particular direction or pattern.

At this point the explanations can get very complicated and as this guide is directed toward people from all walks of life then we’ll simply say that the higher the gain, the better the antenna’s performance and range (over simplification). However antennas with very high gain may also be more expensive, often to reflect their quality, and so there’s something to be said for picking one in the middle ground (note that for every c.6dBi in gain, you could double the range of an antenna).

Some antennas may also give several different gain values to reflect the range of spectrum bands they support, as each may have different characterises due to the antenna design. As such it helps to know what bands your mobile operator is actually using and how to understand the different measures of signal strength (this will help when trying to identify unusual reception problems), which is what we’ll touch on next.

Maps and spectrum bands – finding the info.

One of the biggest challenges with setting up a new antenna is knowing where the signal comes from, how strong it is and which bands are being used in your local area (this can vary depending upon the operator). Vodafone, Three UK, O2 and EE (BT) all have coverage checkers on their websites but these are extremely vague and not always particularly accurate (see Ofcoms Mobile Coverage Checker).

Continued on Page 2..