KENTUCKY PORTABLE CLUB • ANTENNA GUIDES
Hear what the noise is hiding. The Loop on Ground (LoG), Beverage on Ground, K9AY loops and active antennas: what they are, how to build them, and how to hook them up without frying your radio.
On 160, 80 and 40 meters you can usually hear more noise than signal. A receive antenna doesn't make signals louder. It makes the noise quieter, so the signal stands out.
Your transmit antenna is built to radiate well, so it also picks up every noisy power line, charger and TV in the neighborhood. A small, low, "inefficient" receive antenna hears much less of that local noise. Signals read lower on the S-meter, but you copy them better.
Low-band noise is usually stronger than your radio's own internal noise, so you can throw away antenna gain and not lose anything. On 20 m and up, band noise is lower and these antennas help much less.
A LoG is 60 feet of wire on the grass and a little transformer. It packs in a sandwich bag. Lay one out away from the generators and campers and you'll hear 80 m stations nobody else can copy.
Start with the LoG. It's the cheapest, smallest and most forgiving.
A square of insulated wire, about 15 ft per side, lying on the grass. Fed at one corner through a small transformer.
| SPACE | ~20 × 20 ft |
| BANDS | 160–40 m (some use to 20 m) |
| PATTERN | Roughly all-around |
| COST | Under $20 |
A long, straight wire lying on the ground, aimed at the area you want to hear. A resistor to ground at the far end makes it one-way.
| SPACE | 150–300 ft straight run |
| BANDS | 160–40 m |
| PATTERN | Toward the far end |
| COST | Under $25 |
Two triangle-shaped loops at right angles on one ~25 ft support, each with a resistor in it. A relay box picks one of four directions.
| SPACE | ~30 × 30 ft |
| BANDS | 160 & 80 m (40 m OK) |
| PATTERN | 4 switchable directions |
| BEST FOR | Home station |
A small amplified whip ("mini-whip") or an amplified receive loop. Needs power over the coax. Popular for SDRs and web SDRs.
| SPACE | A pole or fence post |
| BANDS | LF to 30 MHz |
| WATCH OUT | Whips hear house noise; mount them away from the house |
| COST | $30–300 |
About an hour of work. Parts: 60 ft of insulated wire, a small ferrite core, some magnet wire, a weatherproof box, a connector and a run of coax.
The corner where the wire ends meet is the feedpoint. Bring both ends into the box and keep the coax leaving the loop at a right angle, along the ground.
| LOOP WIRE | 60 ft of insulated wire, 14–20 AWG. Anything works. |
| TRANSFORMER | About 3:1 turns (9:1 impedance) with separate windings. A mix 73 or 43 binocular core (BN-73-202 or similar) is easy: 3 turns on the coax side, 9 on the loop side. Wiring diagram · Turns helper ↓ |
| FEEDLINE | RG-6 TV coax (75 Ω) is cheap and perfect. F-connectors are fine. |
| CHOKE | A common-mode choke at the radio end, and ideally one at the loop end. Choke recipes |
| PREAMP | Usually needed: 15–25 dB of gain. Your radio's built-in preamp is a fine start. |
| PROTECTION | An RX antenna jack, or a T/R switch that grounds the receive antenna when you transmit. See below |
A long wire on the ground that hears best in one direction. Point it at Europe, the West Coast, or wherever you want to work.
It hears best toward the resistor end. Leave the resistor off and it hears both ways.
Picks the turns for the little transformer between your receive antenna and the coax.
Your transmit antenna puts strong RF into anything nearby, including your receive antenna. Plan for that before you key up.
Many mid-range and higher radios have an "RX ANT" input or an RX-in/RX-out loop on the back. Use it. The radio picks the receive antenna on receive and takes care of switching when you transmit. Check your manual for the jack and the menu setting.
A receive-antenna switch box sits between the radio and both antennas. It listens on the receive antenna and shorts it to ground the moment you transmit. Use one that's keyed by your radio's amp-key / send line, not by RF sensing alone.
Further reading: KK5JY — The Loop on Ground · TAPR — Loop on Ground · KG3V — LoG build
HEAR THEM FIRST
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