RX vs TX Grounding — Totally Different Games

One of the most persistent misconceptions in amateur radio and RF engineering is the assumption of reciprocity in all aspects of antenna systems. Many older RF textbooks state or imply that "what works for receive works for transmit" and vice versa. While the reciprocity theorem holds true for basic antenna radiation and reception patterns under linear, time-invariant conditions, it does not apply when it comes to grounding, common-mode currents, and EMI behavior. We were recently contacted regarding a previous article on using RVS rods to reduce EMI in RX systems, and it's a perfect example of how easily this mistake can mislead well-meaning builders. RX and TX systems require very different grounding strategies.

Receive Grounding (RX): EMI Suppression, High-Z Preferred

In receive-only systems, especially those using active antennas like E-probes or small loops, grounding is primarily about suppressing electromagnetic interference (EMI) and minimizing common-mode current (CMC) on the coax shield. The RF currents involved are typically in the microamp to milliamps range. Here, high impedance paths to ground are often desirable:

Stainless steel (RVS) ground rods are commonly used.

  • These rods introduce high resistance at RF but still allow enough discharge path to bleed off static or shield noise.
  • The skin effect is not a dominant factor because the currents are so low.
  • High-Z grounding prevents the shield from becoming a low-impedance antenna for local noise sources.

This makes RVS rods an excellent choice for receive antennas where the goal is quiet reception and EMI mitigation, not RF current handling.

Nuance: In mixed TX/RX setups—especially where a copper ground is installed at both the antenna base and the shack entrance—RVS rods or stakes placed along the coax route can help reduce EMI on reception. These act as intermediate bleed points for common-mode noise on the coax shield, improving RX quietness even on transmit antennas. While they don’t carry significant RF current, they enhance the RF environment for receive operations. 

For TX antennas like the EFOC or EFHW, which are inherently DC-grounded at the feedpoint, most RF current flows through the radiator—not along the coax shield. In these cases, introducing a high-impedance block (such as a choke) helps prevent shield current caused by skin-effect imbalance. An RVS stake placed at the choke location can provide an effective bleed path for residual common-mode noise without affecting TX performance, since the RF current levels on the shield are minimal. Unlike verticals or center-fed dipoles—where current maxima occur at the feedpoint and require robust low-Z grounding—these end-fed designs benefit more from strategic suppression than brute current handling. Nonetheless, a low-impedance copper or metal ground at the shack entrance is still mandatory for safety and regulatory compliance, though it plays no role in RF grounding.

Transmit Grounding (TX): Current Handling, Low-Z Required

Transmit systems are another story. Now, you're dealing with amps to tens of amps of RF current. Here, grounding needs to be:

  • Low impedance at RF to ensure safe, efficient current return paths.
  • Able to handle high skin-effect surface currents without resistive loss.
  • This is where RVS (stainless steel) fails:
  • It has significantly higher resistance than copper.
  • Its skin depth at HF is poor, making it a lossy conductor for RF.
  • It can heat up or introduce loss in matching systems or feedpoint grounds.

In TX systems, grounding should be done with:

  • Copper rods or wide copper strap for low-Z ground paths on point where grounding is needed like on a conductive mast, static bleeders and shack entrance.
  • Proper common-mode chokes (1:1) on the coaxial line.
  • Ground radials or counterpoises where needed (especially for verticals).

Summary: Context Is Everything

Use Case Grounding Material Purpose Recommended Impedance
RX (active antenna) RVS rod (high-Z) EMI/CMC bleed, static drain High
TX (antenna feed) Copper strap/rod RF current return path Low
TX (CMC choke) Ferrite choke Shield current suppression High (common-mode/skinn effect)
Mixed RX/TX system Copper + RVS combo EMI suppression during RX Hybrid depending on system

Final Thoughts

Grounding in receive systems is about quietness and noise rejection. Grounding in transmit systems is about power handling and efficiency. Confusing the two can lead to poor performance or even damage. Use RVS rods for receive-side EMI suppression, but switch to proper low-Z grounding when it’s time to put watts in the air. And in hybrid systems, consider combining copper and RVS strategically to get the best of both worlds.

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Written by Joeri Van Dooren, ON6URE – RF, electronics and software engineer, complex platform and antenna designer. Founder of RF.Guru. An expert in active and passive antennas, high-power RF transformers, and custom RF solutions, he has also engineered telecom and broadcast hardware, including set-top boxes, transcoders, and E1/T1 switchboards. His expertise spans high-power RF, embedded systems, digital signal processing, and complex software platforms, driving innovation in both amateur and professional communications industries.