Grounding and choking 2025

Keeping the Shack Clean – Fighting RF Noise

 

In a modern radio shack there are many cables: DC power, rotor control lines, relay control, computer connections, and coax lines.
All of these can act as unwanted antennas that pick up or radiate RF noise.

To prevent this, I am systematically adding ferrite chokes and grounding to every cable that enters or leaves the shack.

  • Ferrite chokes block common-mode currents on DC, control and coax cables.

  • Proper grounding with copper strips and a single ground point keeps all equipment at the same potential, reducing loops and interference.

The goal is simple:
👉 Keep the RF energy where it belongs – in the antenna system – and keep noise away from sensitive equipment.

This makes the station cleaner, more reliable, and ensures that both transmit and receive performance are at their best.

 

 

Starting with the Control Cables

The first step in improving my shack was to work on the control cables that run from outside into the shack. These lines can easily pick up RF and bring it straight into the equipment.

To reduce this, I added ferrite chokes on every control cable as soon as it enters the shack. Each cable now passes through multiple ferrite cores to raise common-mode impedance and block unwanted RF currents.

The exact values of the chokes can always be optimized further, but this setup already makes a big difference. It’s a solid starting point that improves receive performance and lowers interference inside the shack.

This way, the control cables are no longer a weak spot, and the RF energy stays where it belongs – in the antenna system.

 

 

 

Grounding the Control Cable Grounds

The next important step was connecting all the grounds of the control cables directly to a single ground bar.
This copper braid is bonded to my main ground system and provides a clean, low-impedance path for unwanted currents.

By tying every control cable ground together at this point, I prevent potential differences and reduce the chance of common-mode currents sneaking into the shack.

It’s a simple but very effective improvement: grounding everything at one place already makes the whole setup more stable and quiet.

DC Power Distribution

In the picture you can see my DC distribution units, which are used to power all the peripheral equipment in the shack. These include controllers, switches, and other support electronics.

The DC distributors blocks are mounted on the grounding bar in the shack.

My transceivers and amplifiers are connected to a separate power supply to ensure stable and interference-free operation.

An important detail: All DC negatives are bonded to the shack ground bar. This provides a common reference point and helps to avoid noise issues and unwanted voltage differences.

 

DC Cables and Chokes

All DC cables in my shack are equipped with ferrite chokes at two points:

  • One choke is placed at the distribution point of the power supply.

  • A second choke is placed close to the device being powered.

This ensures that any unwanted HF currents traveling along the cables are suppressed both at the source and right before entering the equipment. As a result, the risk of RFI is greatly reduced and all accessories continue to operate reliably, even at high transmit power.

In addition, all cables are properly labeled, making the setup organized and easy to maintain.

Remote RX System

For my remote RX system, I paid extra attention to suppressing interference using chokes. These are placed at multiple points in the chain to block unwanted common-mode signals as effectively as possible.

  • Inside the shack: a choke is installed right at the transceiver.

  • At the remote RX distributor: there is a choke right before the distributor, and additional chokes are built into the distributor itself.

  • Future expansion: when the RX is placed outside, it will also get a choke directly at the RX unit. On top of that, another choke will be added just before the cables enter the shack.

With this layered approach, the chance of interference traveling along the RX lines into the shack is minimized, keeping the reception clean even with strong transmit power or local noise sources.

 

 

 

 

Grounding the Transmitter and Amplifier

 

Both my transmitter and amplifier are bonded with a short, thick braided grounding strap to the shack ground bar.

I use a braided strap instead of a single solid wire because the braid offers a much lower impedance to RF currents. At radio frequencies, it is not just about resistance, but mainly about inductance and surface area. The wide, flat surface of a braid provides better conductivity for high-frequency currents compared to a round solid cable.

Additionally, the grounding strap is kept as short as possible, minimizing the path length for any unwanted currents. This reduces potential RF feedback, improves safety, and ensures stable operation of the transmitter and amplifier, even at high power levels.

 

Grounding/Filtering the ALS-600 Power Supply

For my Ameritron ALS-600 amplifier, I added a dedicated ground connection to the power supply. The chassis is bonded directly to the main grounding bar in the shack using a wide braided copper strap.

I use braid instead of solid cable because it provides a much larger surface area, which is especially effective at RF frequencies. The strap is kept as short and direct as possible to minimize impedance and to ensure that any unwanted RF currents are safely directed to ground.

This upgrade improves both safety and performance. It reduces the risk of RF feedback into the amplifier and helps create a clean grounding system where all equipment shares a common reference point.

 

Filtering the ALS-600 Power Supply

Even the mains cable of the Ameritron ALS-600 power supply has been treated against unwanted RF.
Since this cable cannot easily be looped through a large toroid (without removing the factory plug), I used five snap-on ferrite chokes (mix 31) in series.

This solution provides a solid level of common-mode suppression across the HF bands (typically 800–1000 Ω from 3–30 MHz), effectively reducing the chance of RF currents traveling back into the shack through the 230 V line.

While a toroidal core with multiple turns would give a slightly higher impedance, the snap-on approach is the most practical and non-destructive solution here. It ensures the ALS-600 operates cleanly and without introducing noise or RF feedback into the mains network.