The Quectel M26 and M66 are 2G GSM and GPRS modules, while the EC25 is a 4G LTE Cat 4 module with fallback to older networks, and the choice between them is a network-lifespan decision rather than a spec-sheet comparison.
For an SMS device that must keep working for years, the 4G EC25 family protects against 2G shutdowns; for short-life, low-cost designs in markets that still run 2G, the M26 or M66 keeps cost down.
This guide compares the three families on network generation, bands, AT compatibility, power, and integration, and explains how the choice affects a finished SMS modem product.
The Three Families
| Module | Network generation | Typical role |
|---|---|---|
| Quectel M26 | 2G GSM/GPRS | Low-cost SMS and M2M designs |
| Quectel M66 | 2G GSM/GPRS | Compact, cost-sensitive designs |
| Quectel EC25 | 4G LTE Cat 4 with fallback | Long-life SMS and data devices |
The M26 and M66 sit in the same generation: both are 2G GSM modules built for messaging and machine traffic, and they differ mainly in form factor, footprint, and the exact variant options. For SMS throughput, both are governed by the same per-SIM carrier pacing that limits every 2G channel.
The EC25 is a different generation entirely. It is an LTE Cat 4 module, which means higher data rates and a network path that operators are still building, and its fallback behavior keeps the device working where 2G or 3G remains available.
The table is a starting point, not a substitute for the datasheet. Module variants differ by region, band set, and carrier certification, so the comparison should always be re-run against the current datasheet and the target market's network.
Neither 2G module should be chosen without checking the target market's 2G status first, because the network, not the module, sets the device's expiry date.
The M66's compact size is its reason to exist. For an SMS modem with tight enclosure constraints, the smaller footprint simplifies the board layout, but the trade-off is usually in variant options and availability, so compare the two 2G modules on the specific part numbers, not the family names.
The choice also shapes the firmware and test effort: 2G modules have a mature, stable command set, while 4G modules bring more complexity in network registration and fallback handling. Teams with limited engineering capacity often start on 2G for simplicity and move to 4G when the market forces it.
What the Network Generation Decides
Network generation decides how long the device can send, and that is the whole argument for the EC25. 2G shutdowns are underway or announced in many markets, so a device built on the M26 or M66 has a lifespan tied to the local operator's retirement calendar.
The fallback behavior of the EC25 is the practical safety net: where the carrier still runs 3G or 2G, the module can shift down automatically, which keeps an SMS device alive through the migration years instead of failing on a switch-off date.
SMS behavior itself does not change much between generations. A 2G module and a 4G module both submit one message at a time per SIM, so the buyer choosing between the M26 and the EC25 is choosing lifespan and network resilience, not a faster SMS path.
The 2G sunset also affects SIM sourcing. As carriers consolidate portfolios, new 2G-only SIM plans become harder to find, which means a device built on the M26 or M66 may face a supply problem before it faces a network problem; check SIM availability when planning the product's life.
The EC25 is not a single module: regional variants carry different LTE bands and fallback sets, so the choice inside the family matters as much as the family itself. A design that standardizes on one EC25 variant risks failing in markets the variant does not cover.
Band and Coverage Checks
Bands decide whether the module can register in the target market at all. The M26 and M66 carry the GSM bands used for 2G in most regions, while the EC25's LTE bands vary by variant, so the correct EC25 model for Europe may not be the correct one for Asia or the Americas.
The check is simple: list the bands the carrier uses in each target country, compare them with the module variant's band table, and confirm the carrier's certification or approval where the market requires it. A module with the right bands but no approval is a project risk, not a design choice.
Carrier testing belongs in the evaluation. The datasheet lists bands, but registration quality and fallback behavior vary by network, so a test device with the actual SIM in the actual market settles questions the datasheet cannot answer.
Roaming changes the band question. A device that works on the home carrier may need different bands on a roaming partner, and some operators restrict machine traffic while roaming; confirm the roaming terms and bands if the device will move across borders.
Keep a market coverage matrix during evaluation: country, carrier, bands used, module variant, and approval status. The matrix turns a multi-market product decision from a series of conversations into a document the whole team can review and update.
Power and Integration
Power draws differ by generation. A 2G module typically draws less during transmission bursts than a 4G module in LTE mode, which matters for battery-powered designs, while a mains-powered SMS modem absorbs the difference; the power budget should be calculated for the module family, not assumed.
AT compatibility is a practical integration factor. Quectel modules share the general AT command family, so software written for one module often works with another with minor changes, but the details of power management, network registration, and SMS handling can differ, so plan a firmware verification pass when switching families.
The form factor matters for the finished product: footprint, antenna interface, and the availability of a module-to-board adapter affect the enclosure and assembly. Design around the module family that fits the product, then verify the SMS path with the same test harness used in production.
Antenna design is part of integration: the module's antenna port expects a specific impedance and cable, and a mismatched antenna degrades both signal and certification results. Use the reference design from the module vendor for the antenna path, because the module's published performance assumes it.
Thermal behavior belongs in the design review. A 4G module transmitting in LTE mode generates more heat than a 2G module, and a sealed enclosure without airflow can push the module out of its operating range; check the thermal budget, especially for multi-module devices.
Telarvo Expert Views
The module decision is usually made twice: once on the datasheet and once on the market's network roadmap. Teams that pick 2G for cost alone find themselves redesigning when the switch-off is announced, while teams that pick 4G early pay a small premium and skip the forced migration.
— Messaging Solutions Engineer, Telarvo Store
Validation note: module variants, bands, and certifications vary by region; always verify against the current datasheet and carrier approvals.
Conclusion
The M26, M66, and EC25 comparison is a generation decision: 2G modules fit low-cost short-life designs, while the 4G EC25 family protects a device's lifespan, with bands, power, and integration verified per market.
Key Takeaways for B2B Buyers
Choose by network lifespan before price, verify bands and carrier approvals per market, calculate the power budget per generation, and test the module with the real SIM in the real market before committing.
Questions to Ask Before Committing
Ask which module family the device uses, which variants cover your bands, what fallback behavior the module supports, and which carrier certifications are documented.
Ask Telarvo Store which SMS modem models use which module families before you evaluate a configuration.
FAQs
Is the M66 an upgrade over the M26?
They are the same network generation; the M66 is a compact alternative, and the choice depends on footprint and variant availability rather than a generation difference.
Does the EC25 send SMS faster than the M26?
No. SMS throughput is limited by per-SIM carrier pacing, so the EC25's advantage is network lifespan and fallback, not SMS speed.
Can I swap modules without rewriting my software?
Usually with minor changes, because the AT command family is shared, but power and registration details differ; verify the firmware on the new module.
Which module should I choose for a new design?
If the device must last beyond a 2G shutdown, the 4G path is the safer default; use 2G modules only for short-life designs in markets with confirmed 2G longevity.
Are these modules interchangeable in Telarvo products?
Model availability varies by product line; confirm the module family on the product page before assuming compatibility.