====== Placement & Outdoor ======

C-ITS reaches a few hundred metres in a town and a few kilometres with a clear view. Within those limits, where you put the receiver decides almost everything — far more than which board you built. A well-placed cheap receiver beats a badly-placed good one every time.

===== Mounting & line of sight =====

  * **The higher, the better.** This is the single most effective change you can make.
  * **Outdoors beats indoors**, by a lot. Windows reflect 5.9 GHz, and coated or tinted glazing is close to a mirror at this frequency. If you must stay inside, put the node directly against a plain, untinted window facing the road.
  * **Line of sight is what counts.** A free view towards a road, an intersection or a tram line gives the best results. A single building between you and the sender costs more than a few metres of height gain.

The enclosure exists so that the board can be mounted outdoors permanently — on a balcony, a railing or a mast.

===== Interference =====

  * A **5 GHz Wi-Fi access point close by** will degrade reception. 5.9 GHz sits directly next to the Wi-Fi band, and a strong neighbour desensitises the receiver's front end. Either separate the two physically, or switch the access point's 5 GHz band off. This costs you nothing on the receiver side: the official node has no Wi-Fi at all, since its radio is fully occupied with C-ITS.

If reception is poor despite a good mounting position, this is the first thing to check.

===== Antennas & polarization =====

The **antenna printed on the ESP32-C5-WROOM-1 module** already performs very well. Do not assume that an external antenna is automatically an upgrade.

There is also a build variant using the ''ESP32-C5-WROOM-1U'' module, which has a **u.FL connector** for an external antenna instead. Which one to pick, and which pigtail you need, is covered under [[en_alt:receivers#get_one|Get one]].

{{:jlcpcb_externe_antenne.png?0x420|The u.FL variant of the board}}
{{:esp32-c5-ufl.png?0x420|The u.FL connector on the ESP32-C5}}

If you do use an external antenna, **polarization matters more than gain**. We tested this with a Ubiquiti airMAX 16 dBi, on which horizontal and vertical polarization can be connected separately:

{{:pxl_20260628_180745600.jpg?0x420|The Ubiquiti antenna with separate polarization connectors}}

The test setup ran three receivers side by side: the integrated PCB antenna, the external antenna vertically polarized, and the same antenna horizontally polarized.

{{:pxl_20260628_180740889.jpg?0x420|Test setup}}
{{:pxl_20260628_180756944.jpg?0x420|Test setup}}

Comparing the reception heatmaps gives a clear ranking:

  - **Vertical** external antenna — best
  - **PCB antenna** of the ESP32-C5 — very close behind, and no extra hardware
  - **Horizontal** external antenna — clearly worst

**Ubiquiti, vertical**
{{:node99.png?0x420|Reception heatmap, external antenna vertically polarized}}

**ESP32-C5 PCB antenna**
{{:node98.png?0x420|Reception heatmap, integrated PCB antenna}}

**Ubiquiti, horizontal**
{{:node101.png?0x420|Reception heatmap, external antenna horizontally polarized}}

The practical conclusion: unless you have a specific reason and a good antenna, keep the PCB antenna and spend the effort on mounting height instead. If you do go external, mount it vertically.

The heatmaps above come from the [[en_alt:your_node#heatmap|heatmap in the self-service portal]], which is a good way to evaluate your own changes.

===== Temperature =====

  * A typical operating temperature is around **55 °C**.
  * In direct summer sunlight, **more than 83 °C** has been measured inside the enclosure.
  * **Turn the LED brightness down** in the [[en_alt:your_node#node_settings|self-service portal]] (0 = off, 255 = maximum). At full brightness the status LEDs contribute a noticeable amount of heat inside a sealed box.
  * Prefer a **shaded mounting spot**. North-facing, or under an eave, costs nothing and helps considerably.

===== Enclosure =====

The enclosure is 3D-printed, designed in OpenSCAD, and lives in the ''case'' directory of the hardware repository: [[https://codeberg.org/opentrafficmap/its-g5-receiver/src/branch/main/case|its-g5-receiver/case]]

We recommend printing in **ASA**. ASA is UV-resistant without special additives, so the filament manufacturer hardly matters — we always buy the cheapest white one. PLA will not survive a summer outdoors.

For a weatherproof result you need all of it:

  * The printed **bottom seal** (''bottom.stl'') and its screws (M4 × 12, TX20)
  * The **rubber plug** for the LAN cable entry
  * Cable entries facing **downwards**, with a drip loop before the cable enters

===== Surge protection =====

If the receiver is mounted outdoors and its LAN cable runs back to a switch or router indoors, plan for an Ethernet surge protector. A thunderstorm in the area induces voltage spikes on outdoor cable runs, and those spikes travel down the cable into whatever is connected at the far end.

**In short:** one surge protector per outdoor cable run, installed inline **before** the switch, and it **must be grounded**. Without grounding the device does nothing at all.

==== When do you need it? ====

  * Receiver outdoors, switch or router indoors → plan for a surge protector.
  * Fully indoor installation, for example on a windowsill behind glass → not needed.
  * A surge protector guards against **induced** surges from nearby lightning or static build-up. It does not protect against a direct strike — that needs a proper lightning protection concept from a professional.

==== What is at risk? ====

Not primarily the receiver. At around 20 € it is cheap to replace, and so is a PoE injector. The money sits at the **indoor** end of the cable: a PoE switch costs 100 € and upwards, and an unprotected outdoor run feeding into it can destroy it. In the worst case the damage does not stop at the switch — other devices on the same network can be hit as well.

==== Device ====

A proven option is the **Ubiquiti ETH-SP-G2** (Ethernet Surge Protector, around 13 €):

^ Property ^ ETH-SP-G2 ^
| Connection | 2× RJ45, installed inline into the LAN cable |
| PoE | passed through — 802.3af power for the receiver keeps working |
| Data rate | Gigabit-capable; the receiver only uses 100 Mbit anyway |
| Mounting | weatherproof, suitable for outdoor installation |
| Grounding | screw terminal — **the grounding wire is not included** |

==== Installation ====

  * **Position:** inline in the outdoor run, **before the switch** — that is, at the indoor end of the cable, as close as possible to where it enters the building. With several outdoor runs, each run gets its own protector.
  * **Grounding (mandatory):** connect the grounding terminal with **at least 4 mm² copper wire**, green/yellow, to protective earth or the equipotential bonding bar. **Without grounding the surge protector is useless**, because the diverted surge has nowhere to go. Buy the wire separately.
  * **Outdoor connectors:** keep them protected in an outdoor box or under cover, with cable entries facing down and a drip loop. Connectors outside are then uncritical.