You can build a DIY 4G phone around a prototyping board by pairing a host that runs the interface with an LTE modem that handles the cellular connection. The key decision is whether you need mobile data only, SMS, or voice calls: an LTE modem’s advertised features do not guarantee that a specific board, firmware, SIM plan, and carrier will support calls or texts.
What a DIY 4G phone needs
This is a host-board-plus-modem project, not a single-board phone kit. The host runs the screen, controls, and application logic; the modem connects to the cellular network. A usable build also needs a compatible antenna, SIM, suitable power arrangement, and—if you want calls—an audio path and software to manage calls.
Choose your intended services before choosing hardware. Mobile data, SMS, and voice are separate requirements to verify. A modem-family specification may list voice or VoLTE capability without confirming that a particular module SKU, firmware, carrier, and plan can use it.
Choose a build route
| Route | What the cited hardware offers | Best fit | Important checks |
|---|---|---|---|
| Arduino Pro 4G Module | Mini PCIe module for compatible Portenta carrier boards. Arduino describes an EMEA version with Quectel EC200A-EU and a Global version with Quectel EG25-G, LTE Cat.4, and 2G/3G fallback. Arduino Pro 4G Module | A build already using compatible Portenta hardware. | It is not a universal Arduino shield. Confirm the specific module version, carrier-board compatibility, regional bands, and provider acceptance. |
| Arduino-oriented SIM7600 shield | DFRobot links setup instructions, an AT command handbook, and Arduino examples for calls, answering or rejecting calls, SMS, TCP, and GPS. Its guide says D0, D1, and D12 are occupied; D12 connects to the modem power switch, and the module requires external power. DFRobot SIM7600G-H shield | A microcontroller project with a focused interface and direct modem control. | Check the exact shield’s pin use, power input, modem SKU, antennas, and audio connections before wiring. |
| Linux-capable host and modem carrier board | The Strongtek SIM7600G-H board is described with a Raspberry Pi form factor, nano-SIM socket, microphone, audio connectors, antenna connectors, and power/reset controls. SIMCom lists Windows, Linux, and Android USB drivers for the SIM7600 family. Strongtek SIM7600G-H board · SIMCom SIM7600X-H | A richer software interface running on a single-board computer. | Integration depends on board revision, drivers, and modem and carrier configuration. A Linux host can add software flexibility, but typically brings more size, boot complexity, and power demand than a small microcontroller. |
These are distinct hardware routes, not a tested ranking. Compare the exact regional modem variant, host interface, antenna connectors, power input, exposed audio, and how much interface software you want to build.
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Check regional bands and service before buying
Start with the country and provider where you intend to use the device. SIMCom lists different LTE bands for SIM7600-H variants SA-H, JC-H, E-H, NA-H, and G-H R2; Arduino also distinguishes EMEA and Global module versions. “Global” branding by itself does not establish compatibility with your network. Compare the published bands for the exact SKU with the provider’s requirements, then ask the provider whether it accepts the device and will provision the service you need. Band overlap alone does not guarantee registration, data service, SMS, or calls.
SIMCom lists VoLTE as a SIM7600-H family software feature, and its hardware guide describes voice-call support. These are family-level capabilities, not confirmation that voice over LTE is enabled on every board or accepted by every carrier. Verify voice and SMS with the exact modem SKU, firmware, SIM plan, and provider before designing the rest of the project around them.
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Plan the connections and power
Host-to-modem control
Use the interface exposed and supported by the chosen carrier board. SIM7600-family documentation describes UART and USB; a microcontroller shield may expose a particular serial connection and have pins reserved for modem functions. Follow the board’s own pinout and setup guide rather than assuming that another SIM7600 carrier uses the same wiring. DFRobot’s shield guide, for example, identifies D0, D1, and D12 as occupied.
Power supply
SIMCom’s SIM7600 Series Hardware Design V1.02 (2018) specifies a module supply range of 3.4–4.2 V. That is the module supply specification, not necessarily the input voltage you should apply to a carrier board: follow the carrier’s actual input and power recommendations. DFRobot says its shield requires external power. Do not assume the host’s logic supply can power the modem, and do not apply the module supply directly to a board input unless its documentation calls for it. The cited material does not establish one peak-current figure for every module and carrier combination.
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Antennas and audio
The SIM7600 hardware guide identifies main and auxiliary cellular antenna connections and a GNSS antenna path. Use antennas compatible with the selected board’s connectors and the modem’s regional bands. If voice calls are a requirement, check that the carrier board exposes a microphone and speaker or headset path, then confirm the modem, firmware, and provider support the intended voice mode.
Bring up the modem, then build the phone interface
- Define the use and location. Write down the country, provider, and whether the target is data, SMS, voice, or a combination.
- Select the exact modem and host carrier. Match the modem SKU’s bands and interfaces to the provider and board. Confirm that the modem fits the carrier physically and that the carrier exposes the connections you need.
- Wire the board as documented. Connect the supported UART or USB interface, SIM, compatible antennas, and any required external power. Account for pins already assigned to the modem and connect audio hardware if calls are in scope.
- Establish modem control. Use the carrier board’s setup instructions and the modem’s AT command documentation or board examples to communicate with it. DFRobot links SIM7600 examples for tasks such as calls, SMS, TCP, and GPS; the command set and wiring depend on the exact board.
- Add display, input, and application logic. Build the screen and controls on the host. The software must do more than send modem commands: it needs to present status, handle user input, and respond to failures or changes in network state.
- Validate each intended service with the chosen provider. Test network registration and data, SMS, and voice separately as applicable. A working serial link to the modem confirms only that the host can control it; it does not establish that the network has provisioned the service.
Program the modem and interface
For a microcontroller-based build, the host can send AT commands through the interface provided by its shield or carrier. Use examples and command references for that exact board and modem; names such as “SIM7600” do not ensure identical wiring or setup across carriers. A command that starts a call or sends a text is only one part of the application: the interface also needs to show state and deal with unsuccessful operations.
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A Linux-capable single-board computer may make a more software-rich interface practical, while a microcontroller can suit a narrower, dedicated interface. The cited hardware and driver references do not establish a single preferred operating system or compare host performance, so choose based on the software you intend to run and the integration work you are willing to take on.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What modem specifications do—and do not—tell you
SIMCom’s current SIM7600X-H product page lists maximum LTE Cat.4 rates of 150 Mbps downlink and 50 Mbps uplink. These are vendor specifications, not measured speeds for a DIY build; actual results depend on the modem variant, carrier, network, and conditions. The same product page describes drivers for Windows, Linux, and Android, but that does not establish that a particular carrier board will work without board-specific setup.
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Likewise, the 3.4–4.2 V figure applies to the SIM7600 module supply in SIMCom’s 2018 hardware design guide. A carrier board can require a different external input. Keep module specifications separate from the behavior and requirements of the complete board.
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