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Created March 15, 2026 00:45
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light-research.md
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eonist commented Mar 15, 2026

You're right — the SFE-SC is the e-bike version. It has no internal battery, no USB port, no charger. It's just a seatpost with a COB LED strip and a DC power cable that exits from the bottom of the tube. [manuals](https://manuals.plus/m/e90a2aae3f0e8c92d3549d0c600e68dd2efd76fbb2970bc80019d853b1529ad0)

SFE-SC Specs

Wiring on Omera

The cable comes out the bottom of the seatpost, inside the seat tube. From there you route it internally down to the DT electronics module. The path:

SFE-SC cable → inside seat tube → seat tube / DT junction → DT loom → KT light output (6–24V)

You'll need to buy the connector cable separately — Schindelhauer sells it as an accessory for the e-bike version, and it comes in two variants. Or you can just solder your own lead to match whatever connector the SFE-SC has at the bottom. [schindelhauerbikes](https://schindelhauerbikes.com/en/accessories/lightskin-ebike-cable)

Since both the H1E handlebar and the SFE-SC seatpost run on the same DC 6–24V range, you can power both from a single 12V buck converter or directly off the KT light output. Two wires, one voltage, both StVZO-approved — very clean for Omera. [manuals](https://manuals.plus/m/e90a2aae3f0e8c92d3549d0c600e68dd2efd76fbb2970bc80019d853b1529ad0)

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eonist commented Mar 15, 2026

This is a brilliant idea and it works perfectly from an RF physics standpoint. Aluminum blocks GPS/BT signals completely, but plastic (ABS, polycarbonate, nylon) is fully RF-transparent. A plastic top cap becomes an antenna window.eabel+1

Why the Top Cap Is the Ideal Antenna Location

  • GPS needs sky visibility — the top cap faces straight up, unobstructed. Best possible position on the entire bike.

  • Bluetooth needs line-of-sight to a phone in your pocket — top of the steerer, above the frame tubes, is great.

  • The steerer tube is a metal cylinder that would kill signal if you buried the antenna inside it. But with a plastic cap on top, the antenna sits right at the opening, radiating outward.eevblog+1

What Already Exists

There are already AirTag headset top cap mounts — they use a machined aluminum base with a plastic or polycarbonate cover on top, specifically because the AirTag needs to transmit BT through the cap. SpyBike made a dedicated GPS tracker that lived entirely inside a top cap. So the concept is proven.aliexpress+1[youtube]​

How to Do It for Omera

Your electronics module (BT + GPS radio) lives inside the DT. Run a thin coax or antenna feed wire up through the same path as the H1E light cable:

text
DT electronics → HT/DT junction → inside steerer tube → plastic top cap (antenna)

Inside the top cap, mount a small dual-band ceramic patch antenna (GPS L1 + BT 2.4GHz — these are ~15×15mm, a few dollars each). The plastic cap acts as the radome.

For the cap itself:

  • 3D print in ABS or PETG — both are RF-transparent and weather-resistant[eabel]​

  • Match the diameter to standard 1⅛" (28.6mm steerer, ~31.8mm OD cap)

  • Make it thick enough to hide the antenna inside (8–10mm tall)

  • Add a small channel for the coax to exit downward into the steerer

Design Considerations

Factor | Detail -- | -- Cap material | ABS, PETG, or polycarbonate — all RF-transparent [eevblog]​ Antenna type | Ceramic patch, dual GPS L1 (1575 MHz) + BT (2.4 GHz) Antenna size | ~15×15×4mm Ground plane | Small copper disc under the antenna, inside the cap Feed cable | U.FL to the BT/GPS module in the DT Waterproofing | O-ring groove in the cap base, same as AirTag top caps [aliexpress]​

The aluminum steerer tube actually helps here — it acts as a ground plane and shield below the antenna, which can improve the upward radiation pattern for GPS. You get shielding from frame noise below and a clear sky window above.[data-alliance]​

This is honestly a cleaner solution than the plastic console on the DT you were considering for the antenna. The top cap is the highest, most exposed point on the bike — ideal for both GPS and BT. And since you're already routing the H1E light wire through the steerer, adding a thin coax alongside it is trivial.

This is a brilliant idea and it works perfectly from an RF physics standpoint. **Aluminum blocks GPS/BT signals completely, but plastic (ABS, polycarbonate, nylon) is fully RF-transparent**. A plastic top cap becomes an antenna window. [eabel](https://www.eabel.com/aluminum-vs-plastic-enclosure/)

Why the Top Cap Is the Ideal Antenna Location

  • GPS needs sky visibility — the top cap faces straight up, unobstructed. Best possible position on the entire bike.
  • Bluetooth needs line-of-sight to a phone in your pocket — top of the steerer, above the frame tubes, is great.
  • The steerer tube is a metal cylinder that would kill signal if you buried the antenna inside it. But with a plastic cap on top, the antenna sits right at the opening, radiating outward. eevblog

What Already Exists

There are already AirTag headset top cap mounts — they use a machined aluminum base with a plastic or polycarbonate cover on top, specifically because the AirTag needs to transmit BT through the cap. SpyBike made a dedicated GPS tracker that lived entirely inside a top cap. So the concept is proven. aliexpress

How to Do It for Omera

Your electronics module (BT + GPS radio) lives inside the DT. Run a thin coax or antenna feed wire up through the same path as the H1E light cable:

DT electronics → HT/DT junction → inside steerer tube → plastic top cap (antenna)

Inside the top cap, mount a small dual-band ceramic patch antenna (GPS L1 + BT 2.4GHz — these are ~15×15mm, a few dollars each). The plastic cap acts as the radome.

For the cap itself:

  • 3D print in ABS or PETG — both are RF-transparent and weather-resistant [eabel](https://www.eabel.com/aluminum-vs-plastic-enclosure/)
  • Match the diameter to standard 1⅛" (28.6mm steerer, ~31.8mm OD cap)
  • Make it thick enough to hide the antenna inside (8–10mm tall)
  • Add a small channel for the coax to exit downward into the steerer

Design Considerations

Factor Detail
Cap material ABS, PETG, or polycarbonate — all RF-transparent [eevblog](https://www.eevblog.com/forum/beginners/gps-antenna-on-the-aluminum-enclosure/)
Antenna type Ceramic patch, dual GPS L1 (1575 MHz) + BT (2.4 GHz)
Antenna size ~15×15×4mm
Ground plane Small copper disc under the antenna, inside the cap
Feed cable U.FL to the BT/GPS module in the DT
Waterproofing O-ring groove in the cap base, same as AirTag top caps [aliexpress](https://www.aliexpress.com/i/1005007653718300.html)

The aluminum steerer tube actually helps here — it acts as a ground plane and shield below the antenna, which can improve the upward radiation pattern for GPS. You get shielding from frame noise below and a clear sky window above. [data-alliance](https://www.data-alliance.net/blog/antennas-mounted-on-metal-enclosures-guidance)

This is honestly a cleaner solution than the plastic console on the DT you were considering for the antenna. The top cap is the highest, most exposed point on the bike — ideal for both GPS and BT. And since you're already routing the H1E light wire through the steerer, adding a thin coax alongside it is trivial.

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eonist commented Mar 15, 2026

This is a solved problem in the bike industry — every major component maker now offers an internal cable routing (ICR) system through the headset. Since you're designing the Omera frame from scratch, you can pick the approach that works best.

How It Works

All systems share the same core idea: a slotted compression ring sits inside the head tube between the steerer tube and the upper bearing. Cables/hoses pass through the gap between the steerer and the head tube wall, bypassing the bearing entirely. enduro-mtb

The Three Approaches

Oversized upper bearing (industry standard)

Use a 1½" (52mm) upper headset cup with a standard 1⅛" steerer. The ~12mm gap between the steerer and the cup gives plenty of room for brake hoses, the H1E light wire, and antenna coax to pass through. This is what most modern road and gravel frames use. Your head tube just needs a 44mm bore at the top. forum.customframeforum

Semi-integrated (simplest for a custom build)

Use a standard 1⅛" headset with a slotted top cover from brands like Prestine or FIRST Components. The cables exit from under the stem, pass through slots in the top cover/spacers, and drop into the head tube. No proprietary stem needed — you use any stem you want. [prestine.com](https://www.prestine.com.tw/internal-cable-routing)

Fully integrated (cleanest look, most restrictive)

One-piece bar/stem combos (ENVE In-Route, FSA ACR, Deda DCR) where cables disappear entirely inside the bar and exit directly into the headset. Looks incredible but locks you into a specific ecosystem and makes maintenance painful. firstcomponents

What Makes Sense for Omera

The oversized upper bearing approach is the move:

  1. Head tube design: Weld it to accept a 44mm upper cup (IS52 or ZS56 standard) and a standard lower. Prestine and others sell these off the shelf. prestine.com
  2. Cable path: Brake hoses + H1E wire + antenna coax exit the handlebar, wrap under the stem, pass through the slotted top cover, and drop into the gap between the steerer and the 52mm cup.
  3. Inside the head tube: Everything continues down and exits through a 22–35mm access hole at the HT/DT junction into the down tube. [forum.customframeforum](https://forum.customframeforum.com/t/internal-hidden-cable-stems-headsets-and-forks-resource/2473)
  4. Brake hoses split off to the fork (front) and chainstay (rear) at the head tube junction, while the electrical wires continue into the DT.

The Full Routing Bundle

Everything going through the headset in one pass:

Wire/Hose From To
Front brake hose Handlebar lever Fork / front caliper
Rear brake hose Handlebar lever Down tube → chainstay → rear caliper
H1E light DC wire Handlebar DT electronics (KT light output)
Antenna coax (U.FL) Plastic top cap DT electronics (BT/GPS module)

Plastic Top Cap + Antenna

This still works perfectly with the oversized bearing approach. The top cap sits above everything. Replace the standard aluminum top cap with your 3D-printed plastic cap containing the GPS/BT antenna. The slotted compression ring and cable routing happen below it, inside the headset — they don't interact with the top cap at all. prestine.com

So your top cap stack becomes:

[Plastic antenna cap]  ← GPS/BT radome, coax exits downward
[Stem]                 ← clamps steerer
[Slotted spacer(s)]    ← brake hoses + wires pass through slots
[Slotted compression ring] ← sits in the 52mm upper cup
[Upper bearing]        ← standard sealed cartridge

The key frame design detail: make the HT/DT junction hole at least 22mm diameter so all four lines (2 brake hoses + light wire + coax) can pass through without kinking. forum.customframeforum

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