NL-SW-LTE-SCR7611-4 by Airgain — Specs and Selection Reference
Counterfeit cellular modems frequently enter the supply chain with mislabeled speed grades, refurbished internal RF decks, or mismatched carrier certifications. The NL-SW-LTE-SCR7611-4 is an LTE Category 4 module from Airgain designed specifically for AT&T network certification, and its lineage as an integrated antenna-plus-modem solution makes it a prime target for substitution with generic LTE parts. This article provides a procurement specialist’s verification protocol using visual inspection, electrical parameter measurement, X-ray imaging, and Acceptable Quality Level (AQL) sampling to confirm the part identity and performance before committing to volume reels or tray quantities.
Visual and Marking Inspection: Laser Etch vs. Ink and Lot Code Decoding
The authentic module carries a top-side marking that is laser-etched into the molded compound, not ink-printed. Ink printing can be rubbed off with isopropyl alcohol or a fingernail; laser etch survives solvent cleaning and temperature cycling. On legitimate Airgain modules, the marking includes the full part number NL-SW-LTE-SCR7611-4, a traceable two-digit year and two-digit work week (YYWW) lot code, and an alphanumeric serialization on the secondary label. For example, lot code 2340 indicates assembly week 40 of 2023.
Inspect the back of the module for the Airgain logo and the FCC ID or AT&T-specific certification mark. Any deviation in font kerning, logo aspect ratio, or missing regulatory marks is a reject. Store incoming units in ESD-safe bags until the marking check is complete. Procurement action: If 2% of a sample lot shows ink marking, classify the entire lot as suspect and request manufacturer lot trace from the distributor.
Parameter Measurement Methods and Pass/Fail Criteria for CAT 4 Operation
Without a datasheet for the exact die revision, verification relies on measuring typical LTE Cat 4 parameters that should be consistent across the family. Use a spectrum analyzer with a calibrated signal generator and a vector network analyzer (VNA) for the RF path. Set the module into transparent mode with a known good AT&T SIM and measure:
- Maximum downlink throughput: 150 Mbps theoretical for Cat 4. In a test cell with no traffic, sustained throughput above 100 Mbps at -80 dBm RSRP indicates a genuine Cat 4 modem. Below 50 Mbps indicates a Cat 3 or Cat 1 part rebranded.
- Transmitter output power: For a Class 3 modem (23 dBm ± 2 dB), measure conducted power at the antenna port. Output below 19 dBm or above 25 dBm fails specification.
- Rx sensitivity at B12 (700 MHz) and B4 (AWS): Typical reference sensitivity is -95 dBm for 64QAM. If the module cannot decode at -90 dBm, the low-noise amplifier (LNA) may be damaged or from a different generation.
Instrument checklist: Use a Keysight N9020B spectrum analyzer or equivalent, a Rohde & Schwarz CMW500 for LTE signaling, and a 100 MHz bandwidth oscilloscope for power sequencing. Set pass/fail with a guard band of 5% below datasheet limits.
Critical Spec Checklist for Supplier Confirmation
| Parameter | Value | Engineering Meaning |
|---|---|---|
| Configuration | LTE Category 4 | This parameter indicates the peak downlink (150 Mbps) and uplink (50 Mbps) achievable in a 20 MHz carrier. Values above 150 Mbps suggest a Cat 6 or higher part. |
| Carrier Certification | AT&T | Specialty parameter — see datasheet for firmware variant. Using a non-AT&T variant may cause registration failure. |
| Antenna Interface | Diversity + Main | Dual antenna ports enable MIMO; missing a second port indicates single-chain design. |
| Supply Voltage Range | 3.3 V to 4.2 V | This parameter indicates the safe operating range for the module’s internal PMIC. Typical range is 3.3 V nominal; values below 3.0 V may cause brownout. |
| Operating Temperature | -40°C to +85°C | Industrial rating; modules failing above +70°C may be consumer-grade re-reeled. |
| RF Connector Type | U.FL / IPEX | Mechanical fit standard; counterfeit modules sometimes use non-standard snap-locks. |
| Regulatory Status | Active / RoHS Compliant | — |
Interpreting the Critical Specs: What 150 Mbps and Dual Antennas Mean for Your Gateway Design
The LTE Cat 4 throughput ceiling of 150 Mbps is a hardware constraint tied to the chipset’s baseband processing and the number of spatial streams (2×2 MIMO). In a gateway or router design, this limits the usable WAN bandwidth before the modem becomes the bottleneck. If your design targets 300 Mbps aggregate (e.g., dual-radio failover), the NL-SW-LTE-SCR7611-4 must be paired with a load-balancing processor that can queue traffic to avoid bufferbloat. The dual antenna interface is not optional; both ports must be routed to matching ceramic or PCB antennas to achieve the 150 Mbps peak. A single-port implementation will limit throughput to approximately 75 Mbps and reduce cell-edge reliability. For designs requiring AT&T FirstNet or First Priority, confirm the firmware version matches the AT&T IOT certification database, available from the module’s firmware release notes.
X-Ray and Decapsulation Inspection for High-Volume Applications
When procurement volumes exceed 500 units per order, destructive testing on a sample basis using X-ray fluorescence (XRF) and decapsulation provides silicon-level verification. X-ray inspection reveals the die size, bond wire count, and the presence of a shield can. The NL-SW-LTE-SCR7611-4 is known to use a Qualcomm MDM9207 or equivalent baseband; the die should measure approximately 8×8 mm (check against supplier-provided reference images). Count bond wires on the RF section: a genuine Cat 4 modem has at least 12 wires connecting the transceiver die to the antenna ports. XRF of the leadframe material should show a tin-silver-copper alloy, not bare copper or tin-lead (which indicates a non-RoHS part or a recycled scrap package). Decapsulation: soak one unit per 1000 in red fuming nitric acid at 60°C for 2 minutes; the die marking should match Airgain’s internal revision code.
Packaging Verification and Certificate of Authenticity Cross-Check
Verify reel and tray labels against the manufacturer’s standard: each unit is placed in a carrier pocket with a 12 mm or 24 mm tape width (depending on module size). The label must include the manufacturing date code (in YYWW format), the quantity, the part number with no hyphens substituted, and the country of origin. Request a Certificate of Conformance (CoC) from the distributor that includes the specific lot numbers and the test results for conducted power and sensitivity. If the CoC lists a different part number or the lot code is outside the typical shelf life of 2 years from manufacture, elevate the request to the manufacturer direct. Cross-reference sibling parts such as the Gateways, Routers category includes the NL-R-EC4S-VR or NL-S-C4S-V; if the package height or footprint differs from these known references, the part is mischaracterized.
AQL Sampling Plan with Accept/Reject Criteria
For incoming inspection of the NL-SW-LTE-SCR7611-4, follow General Inspection Level II, Normal, per ANSI/ASQ Z1.4 (AQL = 0.65% for critical defects, 1.0% for major defects, 4.0% for minor defects). Use the following defect classification:
- Critical defect (AQL 0.65): Part does not register on AT&T network within 30 seconds with any operational SIM, or shows no RF output on any LTE band. Reject the entire lot immediately.
- Major defect (AQL 1.0): Marking mismatch (wrong font, missing regulatory ID), missing shield can, or conducting RF power 3 dB below the 23 dBm target. Isolate the lot and re-screen 100%.
- Minor defect (AQL 4.0): Scratched plastic, tape residue on label, or non-functional auxiliary GPIO (if not used in design). Accept with corrective action plan from supplier.
Sample size for 5,000-unit lot: 200 units (code letter M); if >2 critical defects or >5 major defects appear, reject and negotiate return with full traceability.
Frequently Asked Questions About NL-SW-LTE-SCR7611-4
Frequently Asked Questions About NL-SW-LTE-SCR7611-4
What is the difference between NL-SW-LTE-SCR7611-4 and the NL-SW-LTE-SCR7611-3 variant?
The -4 variant is certified for AT&T LTE Cat 4, while the -3 variant may be a Cat 3 or carrier-specific alternative. Always confirm the firmware and certification bands; cross-referencing via Airgain’s product matrix is recommended.
How do I verify the firmware version without connecting to a network?
Use the module’s UART AT command port. Send AT+GMR; the response should include a firmware string that matches Airgain’s documented version for AT&T. A mismatch suggests an untested build.
Can I use the NL-SW-LTE-SCR7611-4 as a direct drop-in replacement for a Sierra Wireless MC7455?
No. The physical footprint and U.FL locations are different. The module also uses a different AT command set for carrier aggregation management. A full PCB layout redesign is required.
Where can I find the mechanical drawing for the module?
Airgain provides a mechanical outline drawing in the official datasheet package. Contact your distributor for the latest revision; they may also provide a 3D STEP file for PCB integration.
Procurement workflow summary: Begin with a 50-unit pilot sample and perform all RF parameter tests. If throughput, power, and sensitivity are within 5% of the ranges above, move to AQL Level II for the first production batch. Always keep one sample from each lot for decap X-ray if the application is mission-critical. The NL-SW-LTE-SCR7611-4 is a robust module for AT&T-bound gateways, but only rigorous inbound verification protects against the economic and schedule damage of counterfeit wireless silicon.
