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dBi: Wi-Fi Broadcasting Power and Antenna Explained—There’s no “High-Gain”

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This post is a supplement to my other piece on dBm. I'll explain here how a router's antennas work and another specification relating to Wi-Fi coverage, the dBi, of which the values generally indicate the so-called high-gain antennas.

As it turns out, dBi generally doesn't mean much for Wi-Fi. It's something you shouldn't pay much attention to, if at all. That is why most networking vendors don't list this value in their home products, and those that do, do so solely for marketing purposes.

The bottom line is this: Don't use dBi as a factor in choosing a home router or access point. Also, leave those antennas alone—other than keeping them open up when possible, there's not much else you should do with them.

You can keep that knowledge and move on. Or better yet, stay and continue with the rest—this post can be a fun read on a slow news day.

TP-Link Archer GX90 AX6600 Wi-Fi 6 Tri-Band Gaming Router
Wi-Fi dBi and high-gain antenna explained: All home routers come with their own set of antennas.

What is dBi

To understand dBi, we first need to understand dB or decibels. Again, I detailed it in this post on dBm and Wi-Fi signal strength, but here's the gist:

  • dB is a logarithmic measurement. It doesn't increase or decrease consistently but spirally.
  • Other than the level of sound, dB is a logarithmic way to convey other material properties.
  • dBm (decibel milliwatt) is an example where dB is used to measure power level or signal sensitivity.
  • In the US, per regulations, each Wi-Fi radio band has a max power level of 30 dBm (or 1 watt).

dBm: The power and strength of Wi-Fi signals

With that, dBi is decibel isotropic. It's a logarithmic way to convey an object's physical property measured in different directions.

Specifically, 0 dBi means the object emits radio waves equally in all directions. That's like a sphere with the emitter right in the center.

Since we can't see radio waves, you can imagine 0 dBi as how lights are emitted from a single source, like the sun or a light bulb. It goes out equally in all directions or omnidirectionally.

Theoretically, when you increase the dBi to higher than zero, the signal sphere starts to change its shape—it's no longer a perfect orb. In reality, that depends.

That's because, in our case, the object is a Wi-Fi antenna, and the property is the radio signals it pushes out. And the whole thing is very complicated.

Let's back up a bit.

High-gain antennas: It’s about directional focus

Antennas are not exclusive to Wi-Fi. All radio-based applications require these little poles to broadcast and receive signals.

In telecommunication, we often want to talk to a party in a specific direction.

For example, if you're off-roading in a caravan, the first car generally wants to talk via radio to those behind it, and the last wants to talk only to those in front of it. In this case, it makes sense to focus the antennas in two specific directions: behind and front. So, chances are the cars will use directional antennas.

With this type of antenna, the signals go farther in one direction (gain) at the expense of other (often opposite) directions (loss).

Wi-Fi dBi and high-gain antenna explained: Antenna coverage and dBi (for illustration purposes only.)
Wi-Fi dBi and high-gain antenna explained: Antenna coverage and dBi (for illustration purposes only—real-life signals go out in three dimensions.)

The higher the dBi value, the more focused the signals in the gain direction—the farther it can go—and the larger the area where there's no signal.

Generally, directional antennas use 9 dBi or higher values, up to 24 dBi. However, the number varies depending on the specific device or application.

You can think of directional antennas as your flashlight. The more you focus the light, the narrower the beam and the farther it goes, but the less bright the area outside the beam is.

And when you use a flashlight, there's no light behind you. Still, the flashlight has the same light output as when you remove the reflector and let the bulb emit omnidirectionally.

The gist of this is that there's no "gain" in signals. You only take them from one direction to concentrate on another. The total signal output remains the same. Almost.

In reality, using focused signals always results in some loss of total output due to overheads. (For example, a flashlight's reflector doesn't reflect 100% of the light that hits it—it absorbs some and turns that into heat.)

But in large-area coverage, directional (a.k.a high-gain) antennas are practical for specific applications like FM radio or cellular signals—depending on where you place the antennas, chances are you need to cover more in one direction than others.

OK, and that brings us back to Wi-Fi and its antennas.

Wi-Fi and antennas: There’s no gain

All home Wi-Fi broadcasters—routers and access points—are omnidirectional (no gain) for good reasons.

First, that's because Wi-Fi signals are short in range due to the high frequencies—we're talking about 2.4GHz, 5GHz, and 6GHz here. Omnidirectional allows the hardware to work most efficiently.

And secondly, omnidirectional is the best and safest design since it will fit all homes.

If you get a directional broadcaster, you need a professional to find out where and how to mount it in a particular place so that nobody will use the area where there's no signal. The idea is impractical for vendors and even risky in customer satisfaction. (Imagine standing right next to your router and getting no signal at all because you pick the wrong side.)

That said, all networking vendors generally try to make their home Wi-Fi broadcaster emit signals generically as a sphere. But this is no easy task—it's virtually impossible.

Netgear RAX120 Internal Fan
Wi-Fi dBi and high-gain antenna explained: The top of the Netgear RAX120 Wi-Fi 6 router—note its internal fan.

FEM: Antennas, dBi, and the max Wi-Fi broadcasting power

The dBi value generally applies only to the antennas and doesn't work the same in all vendors. That's because how the signals come out of a router (or an access point) depends on the device's Front-End Module (FEM).

Typically, a FEM includes a few power and low-noise amplifiers, an acoustic filter, and a handful of other hardware components. It's a complicated and technically proprietary device.

You can understand FEM as part of the Wi-Fi System on a chip (SoC) that works with the router's firmware to determine how Wi-Fi signals emit from the hardware's antennas.

The goal of a home Wi-Fi broadcaster is always to have the best combination of three elements: the most extensive Wi-Fi coverage (perfect sphere), the highest Wi-Fi signal strength, and the best compatibility—the support of the clients is essential. All are equally important.

And how FEM works with a particular antenna design within the constraint of the max broadcasting power allowed—30 dBm in the US—to deliver that goal is a well-guarded secret of each vendor. That's what makes one networking brand or specific router better or worse than others.

Wi-Fi broadcasting power limit

In the US, the 30 dBm (1 watt) max broadcasting power applies to all existing Wi-Fi standards, including Wi-Fi 6 and Wi-Fi 6E. That's the highest in the world—the allowed Wi-Fi power levels in the EU and Japan are 20 dBm and 10 dBm, respectively.

Broadcasters of the latest Wi-Fi 7 standard might have a new level of allowed broadcasting power thanks to AFC.

This power level is not to be confused with hardware power consumption in terms of electricity, which depends on the processing power (CPU, RAM, Flash) and other hardware components, such as USB ports, network ports, PoE features, etc. There's generally no regulated limit on a device's power consumption, but lower is always better.

Some broadcasters allow users to adjust Wi-Fi broadcasting power. In this case, the maximum level is the top allowed by the region.

That said, the antennas are just part of the equation. But all home Wi-Fi broadcaster comes with their own set of antennas, explicitly designed for the particular FEM.

Generally, none of the home Wi-Fi routers broadcast signals as a perfect sphere—that's not possible. Most of the time, the signal outputs are in the shape of an egg or a distorted orb.

Wi-Fi broadcasters: Size matters

A common thing among Wi-Fi routers: using firmware to manipulate FEM and antennas requires a lot of processing power. That's where a router's CPU and system memory (RAM) comes into play.

And that's also why if you want a powerful router with extensive coverage, you must find one of the certain physical sizes—larger is generally more powerful.

Some routers have so much processing power that they even have internal fans—like the Asus RT-AX89X, Netgear RAX120, or Ubiquiti UDM.

In short, compact, cute, quiet, extensive coverage, and fast connection speeds are an impossible combo in Wi-Fi hardware.

Common dBi values of home routers: It’s rather meaningless

A Wi-Fi broadcaster uses between 2 dBi and 6 dBi. Its FEM will work within those values to deliver the best signal output—as close to a sphere as possible. Again, the algorithm is a secret.

What's not a secret is that there is no situation where we have a broadcaster that uses the perfect zero dBi value. The reason is other elements of its FEM are not perfect, either. That's not to mention the whole system has to adjust for hardware interference and overhead.

That said, revealing the dBi value in a home Wi-Fi router is meaningless. That's purely for marketing purposes or as a comparison baseline for similar hardware. For the number to make sense individually, the vendor must disclose how its FEM works, too—none does.

That's why you shouldn't care about dBi when picking a home Wi-Fi broadcaster.

Home networking vendors that focus on the broadcasting power via high dBi value tend not to do well in business—they often fail to deliver real-world performance to match the bogus antenna "gain."

Amped Wireless is an example. The company made a big splash a few years ago, advertising tens of thousands of square feet of coverage for its Wi-Fi 5 routers. It hasn't done well since, not surprisingly.

High-gain Wi-Fi antennas exist, but they apply only to specific enterprise applications. They are used mainly to deliver broadband over long distances in rural areas. In this case, particular broadcasters and receivers are used, and at each endpoint, the signals need to be converted by a home router to support regular clients.

If you deliberately turn a standard Wi-Fi router's signals directional, you'll risk distorting them from the intended patterns created by its FEM, rendering them useless on the receiving end.


Common questions relating to Wi-Fi antennas

And that brings us to a few frequently asked questions about Wi-Fi antennas.

Do more antennas mean better Wi-Fi speeds?

Not necessarily. Generally, a router needs one antenna for each band. So, a dual-band router will have at least two antennas. After that, additional antennas are for extra features, such as MU-MIMO, Beamforming, etc.

Important: Antennas don't necessarily equal pieces of metals or the little poles that stick out. They can be part of a device and determined by the FEM and the firmware. A Tri-band or Dual-band receiver can have just one piece of physical "antenna".

But even then, more antennas don't necessarily mean more features. Also, the number of antennas doesn't change the range of a router.

In other words, they change the type of coverage but not the range itself. So more antennas might mean faster speed grades, but not always so.

That's because, ultimately, it's how the router's FEM and firmware handle its antennas that matters. A Wi-Fi connection's speed takes two; the client also needs to support the feature and speed grade of the router for the goodness to happen.

In short, there's no need to get too hung up on the number of the little poles sticking out of our Wi-Fi box.

My home is sprawling. Is it wise to use third-party or directional antennas on my router?

The general answer is no. That's because most vendors don't make directional antennas for their broadcasters, and third-party ones don't usually work as you might hope, if at all.

On the other hand, you can use generic antennas at the receiving end -- they are just passive pieces of metal. For example, if you get a TP-Link Wi-Fi adapter, you can use the antennas of an Asus on it—most of the time, they fit.

Again, there are directional Wi-Fi antennas, but most a made for outdoor applications. So, if you have a specific broadcaster that includes its purpose-built directional antennas, and specific receiver, you can give that a try.

Keep in mind that, in this case, you might not get any signal from the device in some directions, even when you're next to it.

Ubiquiti UDM UniFi Dream Machine
Wi-Fi dBi and high-gain antenna explained: There's no antenna sticking out of this UniFi Dream Machine, but it's still an excellent router.

How do I angle the antennas for the best performance?

You can't. At most, you can only make "different" performances.

Routers with external antennas generally have a section in their user manual about how they should be handled. But generally, they are supposed to stay vertical to deliver the intended coverage and performance.

If you've read some "tech" websites or watched YouTube videos that gave you "special tricks" to angle a particular router's or an access point's antennas or use tin foil to better the coverage, keep in mind that all of that is bullcrap. If at all, only the hardware vendor has authority on this front, and they almost certainly never reveal the specifics.

Sure, you can change their positions (when possible) to manipulate the shape of the coverage sphere mentioned above a bit. Still, the result is generally unpredictable and varies from one router to another.

Furthermore, the effect would occur at the end of the router's range, where the signal is already too weak—the slight fluctuation will likely produce no meaningful Wi-Fi experience. More often than not, messing around with the antennas will make things worse.

Many routers with external antennas, like the TP-Link Archer GX90, don't allow you to swivel them around. There are also more routers with internal antennas.

That said, when it comes to antennas, don't remove or collapse them—keep them extended. After that, feel free to put them at any angle you'd like. When unsure, leave them all vertical.

What's more important is to place your Wi-Fi broadcaster in an elevated, open place.

Asus ROG STRIX GS-AX5400 Gaming Router
Wi-Fi dBi and high-gain antenna explained: Feel free to angle a router's antennas however you want, but generally, vertical is the best.

The takeaway

There you go. There's no need to get too hung up on the dBi when shopping for a new home Wi-Fi broadcaster. In most, if not all, cases, it's insignificant. High-gain (directional) antennas are more relevant to non-Wi-Fi radio applications.

If you want to go with directional antennas with Wi-Fi, then dBi is essential, but in this case, you need to hire a professional and use specialized equipment.

However, in Wi-Fi, size does matter. You can't pack a lot of algorithms into a small box without causing heat issues. So it's unrealistic to expect a Wi-Fi router to be compact and good-looking yet deliver top Wi-Fi speeds and extensive coverage. Not gonna happen.

Something has to give. It's a matter of physics (and cost).

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10 thoughts on “dBi: Wi-Fi Broadcasting Power and Antenna Explained—There’s no “High-Gain””

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  1. Hi Dong,
    A couple of antennas were broken on my GT AX11000. Can the broken AX11000 tri-band wifi 6 antennas be replaced with tri-band wifi 5 antennas of its ancestor AC5300 or even with dual-band wifi 5 or 6 antennas of AC88U or AX88U? There could be a performance or range drop when using these ASUS antennas?

    Thanks!

    Reply
    • I’d tentatively say no, Jacob. In most Asus routers, the parts that stick out of the antennas are passive. But you can’t abuse that, either. Give it a try, chances are you’ll have the same experience.

      Reply
  2. Does wall mounting a router like the ASUS RT-AXE7800 degrade the coverage because the antennas are now flipped sideways?

    Reply
  3. Dong,
    I’m having difficulty with this article. A zero dBi antenna is a sphere, a point source. A half-wave antenna, which most routers have (if their antennae are external) is about 6 dBi … and the router manufacturer, in order not to exceed 30 dBm of radiated power (ERP) reduces the power of the FEM by 6 db (from 1 watt RF down to 1/4 watt of RF power).

    The 1/2 wave-length antenna radiates RF in a donut-shaped pattern. Like a donut dropped down over the antenna rod. It’s a full circle in the one plane, but has increased signal strength in the plane at right angles to the antenna rod.

    Right ?? Comments ??

    Reply
    • All that depends on the FEM, Mike, which is an unknown variant. And to be honest, I’m not a physicist. Most of these are above me.

      Reply
  4. Hi,
    What about the beamforming and steering aspects?
    From the FCC teardown photos, it looks like each antenna on a router typically has a feed from each band’s transmitter. So 4/6/8 antennas are available per band that could form a steered beam by phase control.
    Do you have any insight into what they do in routers? Like packet-to-packet steering, etc.?
    Thanks much.

    BTW, great site and info from you!

    Reply
    • Hi Denny,

      Beamforming is generally proprietary and works within supported hardware (mostly of the same vendor). Band-steering (a.k.a Smart Connect) doesn’t work very well in home broadcasters. I’d just separate the bands as different SSIDs.

      Reply
    • Hello,
      1. Note the “generally” notion in the sentence.
      2. The XT8 has NO external antennas. Whatever angle its internal antennas use is designed specifically to work with its FEM.

      Reply

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