T-Mobile High Speed 5G Internet Gateway (Nokia 5G21) External Antenna Guide


Looking to get the best possible data rates from your T-Mobile 5G Internet Gateway?

You’ll want to purchase and connect external MIMO antennas to the device’s internal U.FL ports.

In this guide, we'll:

  • Recommend the best external antennas to use.
  • Show you how to access the internal U.FL antenna ports, and how to install adapters for external antennas.
  • Explain how to aim the antennas for best results.

Got T-Mobile's newer, boxier hotspot with the display on the front? Check out our guide for that device here.

In this guide

Important Note: To connect external antennas you'll need to open your T-Mobile Gateway. Read our instructions for doing so carefully to avoid damaging the device. Gateways are owned by T-Mobile, and they may charge you a repair fee if you return a damaged gateway device.

The Best External Antennas For the T-Mobile 5G Internet Gateway

Using a MIMO antenna outside your building, pointed at the nearest tower, can help you get the fastest 4G LTE and 5G data rates possible.

The T-Mobile 5G Internet Gateway has four internal U.FL ports, which allow for two 2x2 MIMO antennas or a 4x4 MIMO antenna to be connected to the device.

Accessing the antenna ports does require some disassembly. And we recommend being careful: if you damage the device and then later return it, T-Mobile can charge you a damage fee. Our instructions below guide you through how to connect and test antennas without damaging the device.

We recommend two different MIMO antenna options for use with the T-Mobile 5G Internet Gateway:

Best Seller

This MIMO panel antenna kit will provide meaningful signal improvement, even if you're surrounded by trees, hills, or tall buildings.

For most users the best external antenna choice for the T-Mobile 5G Internet Gateway is our 2x2 MIMO Panel Antenna kit. This antenna doesn’t require line-of-sight to the tower.

Best Performance, Using All Four Antenna Ports

Using all four antenna ports on the T-Mobile Gateway enables 4x4 MIMO, and often results in higher performance.

These cross polarized log periodic antennas have higher gain and are more directional, but work best if you have direct line-of-sight to the tower.

However, if you have line of sight to the nearest tower, we recommend using a 4x4 MIMO log periodic antenna kit instead. This uses four antennas and enables 4x4 MIMO performance, which can often increase your data speeds. The higher gain on these antennas can also get you better performance, but only when you have a straight shot to the tower.

Most folks will see the biggest improvement with a 2x2 MIMO antenna kit like the ones linked above. If you'd like to experiment with upgrading to a 4x4 MIMO setup, this can occasionally yield even higher data rates.

To benefit from 4x4 MIMO, you'll need to use two of our MIMO antenna kits together and connect them to all four internal U.FL antenna ports. Then, separate the actual antenas by about 3 - 6 feet and aim them at the same tower to get 4x4 speeds.

Why External Antennas Are Critical for Improving Data Rates

There's one big misconception about external antennas.

Most people think that external antennas primarily help you increase your data rates by increasing the signal strength.

But that's not the case.

An increase in signal strength is actually probably the third most important way that external antennas help.

Here are the three main ways that external antennas help you increase your data rates:

1.They Improve Signal Quality

In 4G LTE and 5G networks, signal quality is measured as SINR (Signal to Interference plus Noise Ratio) or sometimes as RSRQ (Reference Signal Received Quality).

Improving signal quality has a huge impact on your data rates.

Higher data rates allow your hotspot to communicate using "higher order modulation schemes." That means they can use the same wireless spectrum to send more data per second.

However, there's one big caveat:

In order to improve your signal quality, you need to both aim and shield your outdoor antenna properly. We talk more about this in the next section.

2.They Allow You To Connect On More Bands

Hotspots like the T-Mobile 5G Internet Gateway support a feature called "carrier aggregation."

Carrier aggregation allows the Gateway to connect on multiple cellular bands simultaneously.

The more bands you're connected on, the greater the bandwidth, and the higher your data rates.

However, many of the higher frequency bands aren't able to penetrate into buildings. Using external antennas allows you to access higher frequency bands, which are often less congested and offer higher speeds than lower frequency bands.

3.They Increase Your Signal Strength

As you might expect, using outdoor directional antennas can help increase the signal strength.

This helps increase data rates, but only up to a point.

If your signal strength (called "RSRP" in 4G and 5G networks) is stronger than about -100 dBm, stronger signal won't speed up your connection any further.

Installing External Antennas to the T-Mobile 5G Internet Gateway

Before getting started, it's always a good idea to run a couple of speed tests indoors from a device connected to your Gateway's WiFi. The results will fluctuate a little, but this is the baseline you're trying to improve.

Once you've tested your baseline internet speeds, you're ready to install external antennas. The T-Mobile 5G Internet Gateway doesn't have any external antenna ports, but it's possible to access the internal ports and install adapters that allow you to connect antennas.

In the next section of this guide, we'll show you how to open up your Gateway, connect adapters for external antennas, and close it back up.

Before you get started, you will need the following:

  • A small phillips head screwdriver
  • A Torx T10 screwdriver
  • A thin plastic prying tool (old bank cards work fine too)
  • Needle-nose pliers or tweezers
  • Two U.FL-male to N-female pigtail adapters (included in our External Antenna kit)
  • Some electrical tape
  • A secure container to keep screws and small parts safe while you work
Important note:

Be careful not to damage your T-Mobile Home Internet Gateway while disassembling.

As part of your agreement with T-Mobile, you "borrow" this equipment from them. When you end your service, you'll likely need to return the gateway to T-Mobile. If there's damage to the device they are contractually able to charge you up to $370 in damage fees.

Waveform does not make any guarantees nor take any responsibility for damage caused to your unit when following these instructions. Please proceed at your own risk.

If you do decide to return your unit to T-Mobile, make sure to reconnect the existing internal antenna connectors before doing so.

Step-by-Step Guide to Installing Adapters for External Antennas

Step 1: Power off the T-Mobile 5G Internet Gateway and unplug the power cable.

Step 2: Unscrew the Phillips head screw securing the SIM card holder and remove the SIM card holder, as pointed at by the top arrow below.

Step 3: Unscrew the two T10 screws from the bottom cover.

Unscrew the two T10 screws from the bottom cover

Step 4: Gently pull the bottom cover away from the casing until it releases.

Step 4: Release the clip securing the battery, and remove it from the device.

Release the clip securing the battery, and remove it from the device

Step 5: Remove the four T10 screws securing the outer casing in each corner.

Remove the four T10 screws securing the outer casing in each corner

Step 6: Now remove the outer casing. Be careful not to damage the clips on any of the ethernet ports, and ensure the power button stays in the off position (pushed out) when sliding the casing off.

Remove the outer casing

Step 7: Rotate the gateway to see a series of black cables connected to the board by small U.Fl connectors. There are a total of four U.FL connectors for use with cellular antennas, two on either side of the purple GPS connector. Depending on which MIMO Antenna kit you are installing, two or four of these cables will be disconnected:

  • If you have a 2x2 MIMO Antenna Kit, use a prying tool or pair of tweezers to very carefully disconnect the two cables to the right of the purple cable. Do not alter the remaining cables.
  • If you have a 4x4 MIMO Antenna Kit, use a prying tool or pair of tweezers to very carefully disconnect all four of these cables.

Note: Be very careful. U.Fl connectors can be quite fragile. Make sure you're very gentle to avoid breaking the connector when disconnecting it from the board.

Once the U.Fl cables for the internal antennas are fully disconnected, coil them into the open spaces above and below the board, as shown here:

Disconnect the U.FL cables for the internal antennas

Step 8: Route your pigtail adapters through both sets of vent ports on the bottom stand (the vents are around the circumference and going inside the unit).

Note: Try to route the pigtails through the vents that will be close to the ports on the device to avoid any sharp bends and excessive force on the cables once re-assembled.

Route your pigtail adapters through the vent ports

Step 9: Install your U.FL-male to N-female pigtail adapters by very carefully aligning and pressing them down into the ports you opened up in step 8. A quiet "click" can often be heard once the connectors are pressed down and fully connected.

Install the U.FL to SMA-female pigtail adapters into the ports you opened up in step 7

Step 10 (optional): Use electrical tape to secure your pigtail adapters to the frame. This helps prevent the cables from being tugged on and damaging the U.Fl connectors.

Step 11: Reassemble everything in reverse order. Make sure that your power button is in the off position before reconnecting the battery.

Reassemble the gateway

Congrats! Your T-Mobile 5G Internet Gateway should now be fully re-assembled, with the pigtail adapters protruding from the bottom. You are now ready to connect your external antenna(s) to the adapters you installed into your Gateway.

Fully completed installation.

Thanks to Eric Durham and XMRFreak on Reddit for allowing us to use these images.

Positioning and Aiming MIMO Antennas

Positioning and aiming MIMO antennas well is crucial to getting the best performance to your T-Mobile 5G Internet Gateway, or indeed any other hotspot.

We've actually compiled a detailed 2x2 MIMO instruction manual and 4x4 MIMO instruction manual to accompany our own MIMO Antenna Kits, where we go into depth on the best ways to aim the antennas.

The goal is to find the best location and direction for the antenna(s), to maximize data rates to the T-Mobile Gateway. It can take a little patience, but can have a huge impact – it’s worth a bit of extra effort!

Connect your MIMO external antennas to your modified T-Mobile 5G Internet Gateway via the newly installed pigtail adapters, and go outside with your "test-rig".

With each location and direction you try, run a couple speed tests, and make a note of the results. Here are all the locations and directions where we recommend testing your MIMO antenna:

Where to test your signal

Where to test your signal

Pro tip: Don’t just go to the highest point of the roof! While signal is generally stronger the higher you go, there’s also often more interference. We’ve found it’s often better to mount the antenna(s) on the side of the building where the structure can shield the antennas from interference.

Once you've found the position which gets you the highest data rates to the T-Mobile Gateway, that's where you'll want to install the MIMO antenna. Go ahead and mount the antenna, run cables inside, connect everything up, and enjoy superior data rates!

T-Mobile 5G Internet Gateway Technical Specifcations

Supported T-Mobile bands in the US

  • 5G Bands: n2, n25, n41, n66, n71
  • 4G LTE Bands: B2, B4, B5, B12, B25, B26, B41, B46, B48, B66, B71

Cellular Modem

  • Model: Qualcomm Snapdragon X55
  • MIMO Support: 4x4 w/ internal antennas or external antennas
  • LTE-A Carrier Aggregation: Yes (5x 20 MHz bands)
  • LTE Performance Category: Cat 20
  • Max Theoretical Speeds: 2.5 Gbps Download, 316 Mbps Upload


  • Technologies: 802.11 ax
  • Bands: Simultaneous 2.4 GHz and 5 GHz


  • Cellular Antenna Ports: 4x internal U.FL (two on each side of purple GPS cable)
  • Ethernet Ports: 2x Gigabit LAN ports, 1x Gigabit WAN port
  • Other Ports: 1x USB-C, RJ-11 (voice)


  • Can Be Powered Without a Battery: Yes

Other Helpful Resources

A helpful guide on installing and maintaining U.FL connectors

T-Mobile's support page for the High-Speed 5G Internet Gateway