RF Chokes - 1:1 Current Baluns for HF | Greyline

Feedline Hygiene · Greyline Doctrine

Stop Common-Mode Noise. Keep The Pattern Clean.

If your receive sounds noisier than your noise floor should be, or your shack equipment lights up when you key down, the answer usually lives here. RF chokes and 1:1 current baluns block common-mode current on the feedline — the leak path that turns your coax shield into an unwanted radiator and your shack into a receive antenna for everything you don't want to hear.

What Common-Mode Current Actually Is

Coax is supposed to carry RF inside the cable — center conductor and shield's inner surface. In a clean system, the outer surface of the shield carries no current. In an unclean system, common-mode current flows on the outside of the shield, turning your feedline into part of the antenna.

When that happens, three things go wrong:

Receive noise goes up. Your feedline now picks up every electrical noise source on the way to the radio — LED bulbs, switching power supplies, neighbor's solar inverter, your own house wiring.

Transmit gets dirty. RF in the shack causes everything from headphone hum to keyboard glitches to telephones ringing on their own. RFI is the symptom; common-mode is usually the cause.

Your antenna pattern distorts. A radiating feedline isn't part of your designed antenna. The pattern you tested in modeling isn't the pattern you're running.

The Two Tools In This Collection

RF Choke. A high-impedance block that sits in the feedline and refuses to pass common-mode current. The differential signal (the one you actually want) goes through. The unwanted common-mode hits the wall. Clean install, immediate effect.

1:1 Current Balun. Same job, different geometry. A current balun forces equal-and-opposite current on the two conductors entering the antenna, which mathematically cancels common-mode at the feedpoint. On an HF vertical, the 1:1 current balun is the standard answer.

Which One Do I Need?

For most Greyline VDA installs, a 1:1 current balun at the feedpoint is the cleanest answer. If you're already running a balun and still hearing noise, an additional RF choke further down the feedline (typically near where the coax enters the shack) is the second line of defense.

Belt and suspenders is fine. RF doesn't care about over-engineering. Noise floors do.

Quick Diagnostic Frame

Symptom Likely Cause
Receive noise floor unusually high Common-mode pickup. Add choke or balun.
RFI in shack on transmit Common-mode return through equipment grounds.
Signal touches the radio chassis Feedline radiating. Choke at shack entry.
Pattern doesn't match modeling Coax shield is part of the antenna. Balun.

Built For HF Verticals

Greyline RF chokes and 1:1 current baluns are spec'd specifically for HF vertical antenna systems. Power handling, frequency range, and impedance characteristics are matched to what a Greyline VDA actually does on the air. Not a generic part with a hopeful spec sheet.

Quiet receive. Cleaner transmit. Lower RFI. Pattern stays where it belongs.

The Other Half of the Feedline Story

Quiet Receive AND Low Loss

Common-mode noise is one feedline problem. Power loss in the cable is another. The Greyline Feedline Loss Calculator shows you how much of your transmitter power actually reaches the antenna — pair it with a clean RF choke and you have both halves of the feedline solved.

Open the Calculator →

Pair with: Antenna Tuner Collection → · Feedline Physics → · Feedline System Kits →

73 Greyline — 435-200-4902

Ham Radio is fun again. Pass it on…

4個の商品
  • $65.00
    $65.00
  • $95.00
    $95.00
  • $95.00
    $95.00
  • $65.00
    $65.00