Add GPS_L76k

GPS_L76k.md

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+Below is a focused, technical comparison of the **two GNSS module options** offered for the **LilyGO T-Beam Supreme**, followed by a recommendation specifically for a **mobile unit in the United States**.
+
+---
+
+## GNSS module options on the T-Beam Supreme
+
+![Image](https://files.seeedstudio.com/wiki/Seeeduino-XIAO-Expansion-Board/GPS_Module/L76K/1-L76K-GNSS-Module-for-Seeed-Studio-XIAO-45font.jpg)
+
+![Image](https://content.u-blox.com/sites/default/files/products/NEO-M8-top-bottom.png)
+
+![Image](https://lilygo.cc/cdn/shop/files/LILYGO-T-BEAM_10_3bb84be5-da09-4626-8b93-99be997d49b8.jpg?v=1739257071)
+
+### 1. **Quectel L76K**
+
+**Type:** GNSS (multi-constellation)
+**Constellations supported:**
+
+* GPS (USA)
+* GLONASS (Russia)
+* Galileo (EU)
+* BeiDou (China)
+* QZSS (Japan)
+* SBAS (WAAS in the USA)
+
+**Key characteristics**
+
+* Modern, low-power GNSS chipset
+* Fast cold-start and good tracking sensitivity
+* Designed for wearable and battery-powered devices
+* Small RF footprint; tolerant of sub-optimal antennas
+* Fully supports **WAAS**, which is important in North America
+
+**Operational implications**
+
+* Excellent performance while **moving**
+* More resilient to intermittent sky view (pockets, jackets, dog harnesses)
+* Lower steady-state current draw than older modules
+
+---
+
+### 2. **u-blox NEO-M8 (M8N/M8Q family)**
+
+**Type:** GNSS (multi-constellation, earlier generation)
+
+**Constellations supported (variant-dependent):**
+
+* GPS
+* GLONASS
+* Galileo
+* BeiDou
+* SBAS (WAAS)
+
+**Key characteristics**
+
+* Extremely mature and well-documented chipset
+* Broad tooling support (u-center, extensive configuration options)
+* Slightly higher power consumption than L76K
+* Larger module footprint
+* Very stable long-term operation
+
+**Operational implications**
+
+* Rock-solid for fixed or vehicle-mounted nodes
+* Slightly slower reacquisition when repeatedly blocked/unblocked
+* Power draw matters more in pocket-sized, battery-only devices
+
+---
+
+## Side-by-side summary
+
+| Attribute         | **Quectel L76K**    | **u-blox NEO-M8** |
+| ----------------- | ------------------- | ----------------- |
+| Generation        | Newer               | Older but mature  |
+| Power consumption | **Lower**           | Higher            |
+| Mobile tracking   | **Better**          | Good              |
+| WAAS (USA)        | Yes                 | Yes               |
+| Cold-start speed  | Faster              | Slower            |
+| Tooling ecosystem | Moderate            | **Excellent**     |
+| Best use case     | Wearable / handheld | Fixed / vehicle   |
+
+---
+
+## Recommendation for a **mobile unit in the USA**
+
+For your stated use case—**a mobile unit that may be pocketed, worn, or attached to a dog**—the **Quectel L76K** is the preferable choice.
+
+**Why:**
+
+* Better tolerance of marginal sky visibility
+* Faster reacquisition after brief signal loss
+* Lower power draw → longer battery life
+* Full WAAS support in the United States
+* Optimized for modern low-power GNSS use cases
+
+The **u-blox NEO-M8** remains an excellent module, but its strengths shine more in **vehicle-mounted**, **fixed**, or **externally powered** installations where power and reacquisition latency are less critical.
+
+---
+
+## Practical note (important for mobility)
+
+Regardless of module choice, **antenna orientation and ground plane matter more than chipset choice** in wearable scenarios. A well-matched ceramic or flexible PCB antenna with a decent ground reference will yield more real-world improvement than switching GNSS modules.
+
+If you want, I can:
+
+* Recommend **specific antennas** that pair well with the L76K for pocket or harness use
+* Compare **patch vs. PCB vs. flexible antennas** for your walking scenarios
+* Discuss **assisted-GNSS (A-GNSS)** options when Internet backhaul is occasionally available