The Future of RX: aRFoF vs Coax in QRM-Challenged Environments
The Future of RX: aRFoF vs Coax in QRM-Challenged Environments
In today’s RF landscape, high levels of man-made noise (QRM) make it increasingly difficult to maintain clean receive paths — especially on the low bands like 160 m and 80 m. Even relatively short coaxial runs to remote antennas can become part of the noise problem, not the solution.
Analog RF over Fiber (aRFoF) offers a noise-immune alternative, delivering pristine analog RF signals over short plastic optical fiber (POF) links. While coax remains practical for long-haul runs, fiber has the potential to eliminate the last meters of QRM pickup into the shack.
aRFoF vs. Coax at 10 Meters: A Low-Band Focus
| Parameter | RG6 Coax (75 Ω) | aRFoF (1 mm POF) |
|---|---|---|
| Attenuation (10 m @ 7 MHz) | ~0.26 dB | <0.1 dB (optical + electronics) |
| EMI susceptibility | High | None |
| Ground loop risk | High | None |
| Common-mode pickup | Significant | None |
| Cost per meter | €0.30–0.50 | ~€1–1.50 |
Key takeaway: Even at just 10 m, aRFoF eliminates noise sources coax can still couple in.
QRM Immunity: Fiber Solves the Root Problem
Unlike coax, fiber is dielectric and immune to:
- Radiated EMI from Ethernet, LEDs, or switch-mode PSUs
- Conducted noise from shack power systems
- Ground loops between antenna site and station
How aRFoF Fits Into the RX Chain
- Antenna (passive or active) → RF captured
- aRFoF TX module → converts RF into light
- Plastic optical fiber (POF) → carries signal
- aRFoF RX module → restores RF for the receiver
- Receiver → processes a clean, isolated signal
Unlike digital transport, aRFoF preserves real-time amplitude and phase, critical for phasing and array work.
Hybrid Deployment: Coax + Fiber
For distant antenna sites, a hybrid approach works well:
- Use RG6 for 100–300 m trunk runs (loss manageable with preamps).
- Convert to aRFoF in the last 5–10 m near the shack to eliminate local QRM pickup.
Looking Ahead
At RF.Guru, we believe aRFoF will become a practical alternative to coax in noise-sensitive low-band receive applications. While coax remains a cost-effective, flexible solution for most amateur installations, fiber offers the ultimate in QRM immunity and galvanic isolation.
We plan to tackle this idea in the future by exploring compact analog aRFoF modules optimized for the 1–10 MHz RX band, tailored for active antennas and phased-array use. Once development is underway, we’ll share more technical details and opportunities for real-world testing.
Final Thoughts
For serious low-band DXers in high-QRM environments, coaxial cable is often part of the problem. Even over short distances, analog RF over fiber promises:
- Clean signal paths
- No common-mode currents
- Zero EMI pickup
- Galvanic isolation between shack and antenna site
Mini-FAQ
- Is aRFoF really better than coax at just 5–10 m? — For low-band RX in noisy QTHs, yes. Fiber blocks local EMI and common-mode the last meters cannot avoid.
- Does aRFoF preserve phase for phasing/arrays? — Yes. Analog optical links carry amplitude and phase in real time, suitable for beamforming.
- What are the downsides? — Higher link cost and the need to keep optics clean; electronics must have adequate SFDR to avoid strong-signal compression.
- Can I mix coax and fiber? — Yes. Use coax for long trunk runs, then convert to fiber near the shack to eliminate local QRM pickup.
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