Why Coax Clamps Fail — and Bulkhead Plates Are the Right Way to Ground Your Shack
Why a Bulkhead in an RVS Plate Beats Cutting Your Coax for PE
Some hams still cut into their coax cable and add a clamp or “tap” to connect the protective earth (PE) or ground. While it may look like a quick fix, this practice is technically flawed and can actually degrade both safety and RF performance.
Why Cutting Coax for PE is a Bad Idea
- Weakens the coax shield — Cutting into the braid compromises its integrity, inviting water ingress, oxidation, and mechanical failure.
- Unreliable ground path — A clamp around braid fibers is not a low-impedance, repeatable connection. Under RF, it can act more like a resistive or inductive joint.
- Increased common-mode pickup — By disturbing shield continuity, you create a “leaky coax” segment where unwanted RF currents and noise can enter.
- No compliance — From a safety perspective, a damaged shield does not meet protective earth requirements in many electrical codes.
Why a Bulkhead Through Copper or RVS is Better
The professional solution is a coaxial bulkhead connector mounted through a copper or RVS (stainless steel) plate, with the plate bonded to PE. Modern bulkheads are plated for corrosion resistance and ensure excellent conductivity between coax shield and ground.
- Direct, solid bond — The bulkhead makes a full-surface, low-impedance connection between coax shield and the plate.
- Structural strength — Coax stays intact; strain is handled by the connector, not a fragile clamp on the braid.
- Corrosion resistance — Plated surfaces (nickel, silver, or tin) ensure stable contact with both copper and stainless.
- Proper entry point — A plate acts as a defined RF and safety reference at the shack entrance, instead of random mid-cable taps.
Think of the bulkhead as both a mechanical anchor and an electrical checkpoint — ensuring coax shielding, RF currents, and safety earth are all tied to one robust reference plane.
Standards Say So
This isn’t just good practice — it’s what international standards demand:
- EN 55032 / EN 55035 — EMC requirements assume continuous coaxial shielding until bonded at entry.
- EN 50083-1 and EN 60728-11 — Require coaxial systems to be bonded via proper entry grounding devices, not clamps.
- EN 50310 — Defines equipotential bonding in ICT environments; bulkhead bonding plates are the reference method.
- IEC 60364 / HD 60364 — Mandates durable, corrosion-resistant PE connections; clamps on braid do not qualify.
- IEEE Std 1100 (Emerald Book) — Recommends single-point entry grounding with bulkhead connectors for shield integrity.
- NIST SP 960-6 — On lightning/surge protection, requires low-inductance, mechanically strong bonds — satisfied by bulkhead plates, not mid-cable clamps.
In short: the clamp “solution” is not just poor practice — it’s non-compliant with every professional code.
Mini-FAQ
- Can I just clamp PE directly to coax? — No, this weakens shielding and creates leakage paths. Use a bulkhead.
- Why stainless (RVS) or copper plates? — Both provide a large, conductive reference plane. Stainless is durable outdoors; copper is superior electrically but needs plating or paste to avoid corrosion.
- Do I need plating on the bulkhead? — Yes, plating prevents galvanic corrosion between dissimilar metals and keeps the bond low-impedance long term.
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