RVS Stakes as High Z Termination for RX Shielding & EFHW Counterpoise

In HF (high-frequency) reception and end-fed antenna design below 30 MHz, unconventional techniques sometimes help achieve specific goals. One such approach uses stainless steel (RVS/INOX) stakes as high-impedance terminations—either to reference the shield of a coaxial cable in a receive-only setup or as a counterpoise element in EFHW antennas. Because stainless steel isn’t an ideal conductor, this practice often raises eyebrows in the ham community. So is it valid, or are the skeptics right?

Understanding the Application Context

Criticism usually stems from comparing stainless steel with copper in traditional RF grounding or transmission roles. Copper is preferred for its low resistivity and excellent RF performance, especially for safety grounds and RF return paths where skin effect matters.

However, the context here is different—receive-only systems and counterpoise designs where high impedance is intentional:

• We are not seeking a low-impedance RF ground as we would in a transmission scenario.
• We are not handling high current; we’re dealing with voltage nodes (EFHW) and RF-potential isolation.
• We want to avoid strong coupling to ground, instead using a high-Z termination to limit unwanted RF return currents.

INOX as a High-Impedance Element

Because stainless steel has much higher resistivity than copper or aluminum, it presents higher impedance at RF. That makes it a poor choice where current flow is desired—but potentially a useful feature when the goal is to block or reduce RF current.

Applications

1. RX shield reference (common-mode reduction): In receive-only systems with active antennas (E-probes, active whips), bonding the coax shield to an INOX stake provides a high-Z path to earth that bleeds off static without creating a low-Z RF return. This can reduce common-mode pickup and system noise.
2. High-Z counterpoise for EFHW: For end-fed half-wave antennas where a full radial system isn’t practical, an INOX stake can act as a “soft” counterpoise—offering a high-impedance reference to earth that helps balance the system without inviting strong return currents onto the feedline.
3. Baluns with ground lugs: Where a balun includes a ground lug, an INOX stake can serve as the connection point. Its inherently higher impedance—often compounded by modest soil conductivity—can tame unwanted RF feedback without “hard” grounding the system.

Where INOX Is Not Appropriate

INOX stakes are not universal solutions. If you need a true low-impedance ground—such as for:

• Balanced-line bleeders that must efficiently dissipate common-mode current,
• Mast and equipment safety grounding or lightning protection,

…then a stainless steel stake is the wrong tool. Use copper or galvanized ground rods with good earth contact for safety and performance.

⚠️ If you cannot bond to the building’s protective earth with a low-impedance connection, separate independent ground systems by at least 15–20 meters. This helps reduce ground loops, circulating currents, and potential differences during lightning events or high-power operation.

Product Examples from RF.Guru

RF.Guru offers several grounding options suited to the use cases above:

• Multi-Use RVS/INOX RF Ground Stake: High-impedance termination for RX shield referencing or EFHW counterpoise duties.
• 65 cm Galvanized Grounding Rod: Robust low-Z ground for mast safety and balanced-line bleeders.
• Small RVS Ground Peg: Portable, corrosion-resistant high-Z termination for lightweight RX setups.

Compared with Copper or Galvanized Steel

Using copper in these specific roles may “over-ground” the system, increasing common-mode currents on the coax or upsetting the intended radiation pattern. INOX provides a weak capacitive link to earth and resistive dissipation of static and some RF—generally not enough to dominate system behavior.

Galvanized steel can be similar in RF impedance but typically degrades faster. INOX offers better corrosion resistance and more stable long-term performance.

Measurement

In the test setup, a common-mode signal was injected at the top of an RVS stake using a Tekbox current probe. A coax bulkhead adapter was mounted directly to the stake, which was inserted into ordinary soil to ensure realistic earth contact. A second Tekbox current probe on the output measured the remaining common-mode current to estimate the effective common-mode impedance of the stake-plus-earth combination.

The results show strong low-band attenuation—exceeding 30 dB at 1.8 MHz and remaining above 15 dB up to 10 MHz—demonstrating effective suppression of common-mode currents across much of the HF band.

Above ~20 MHz, attenuation drops to roughly 3–7 dB, consistent with increased capacitive coupling and wavelength effects.

These data confirm that an RVS stake with direct earth contact and an integrated bulkhead presents high common-mode impedance—useful for RF noise reduction and feedline isolation in antenna systems.

Conclusion: Myth or Valid Approach?

In this narrow but important use case, INOX stakes are a valid engineering choice. They are not appropriate for high-power transmission or code-required safety grounds, but they shine when high impedance, corrosion resistance, and stability matter more than conductivity. They are well suited to:

• Reducing unwanted RF currents in receive-only installations,
• Serving as high-Z counterpoise elements in EFHW systems,
• Providing a high-impedance reference for baluns in poor soil conditions.

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