The Signal Lab

The Greyline Standard: Physics & Performance

I. The Physics

Why the VDA Works Without Radials

Traditional quarter-wave verticals are ground-fed monopoles. The antenna feeds at the current maximum at the base, so every ohm of ground resistance sits in series with the radiation resistance — stealing signal before it leaves your yard. The standard solution is a buried radial field: 32 to 120 wires extending outward to create a low-resistance ground plane. On 160 meters, a proper radial field spans roughly 200 feet in every direction. That system runs directly toward your neighbor’s house, their panel, their appliances, and every noise source on the property line.

The Greyline VDA solves this differently. It is a vertical dipole — an OCF (off-center fed) design with an elevated feedpoint. Return current flows through the lower element rather than through a buried radial field, which removes the radial field's loss from the equation and makes performance far less dependent on your soil. The antenna works against itself, not against the earth. Ground still shapes the far-field pattern, as it does for every antenna; what it no longer does is sit in series with your feed.

The result: consistent, predictable performance on concrete, asphalt, rooftop, or frozen ground, in any season. And a 2-inch pole footprint that goes wherever your lot is quietest.

Further reading: Robert Zavrel, Antenna Physics: An Introduction (ARRL, 2020) · John Kraus, Antennas (McGraw-Hill) · the ARRL Antenna Book · Full VDA physics deep dive →

II. Gain Data

dBi Gain by Height and Band

In NEC modeling over average ground, measured against an ideal quarter-wave on a full field of buried radials (0 dBi), here is each Greyline height, with and without the 9-foot whip. These are maximum gain figures at the optimum angle, modeled at total height with the feedpoint section included. Every height works every band; the table shows where each one earns its bonus. Past a certain electrical length on the higher bands, the pattern breaks into lobes — the EDZ region — and that band's energy splits between low and high angles.

NEC modeling over average ground. Maximum gain at optimum angle, against a full-radial quarter-wave at 0 dBi. The runs were made at 12, 16, 20, 24, 29, 33, and 37 feet total height; the 28-foot shares the 29-foot run, one foot apart. EDZ = extended double Zepp region: the pattern breaks into lobes, and the band still works, with its energy split between low and high angles.

Gold values = the strongest band for that height. Every height also works 80, 160, and 6 meters, where more height means more aperture.

III. The “Too Tall” Problem

Smarter, Not Taller: VDA vs. the 43’ Vertical

Height pays — it is aperture, and on 40, 80, and 160 more of it means more signal. The 43-foot vertical is built on that truth. But it is a ground-fed quarter-wave, so it needs an extensive radial field to deliver its length, and on the higher bands its pattern works against it.

With a good radial field under it, a 43-footer is effective from 80 through 30 meters. From 20M through 10M, its electrical length becomes a liability: the pattern rises, sending more signal skyward and less toward the horizon, where the DX is.

The Greyline VDA uses an elevated feedpoint. Return current flows through the lower element rather than a buried radial field. No traps, no coils. In NEC modeling the 28-foot runs ahead of a full-radial quarter-wave from 30 through 15 meters — about +1.1 dBi on 30, +2.3 on 20, +3.5 on 17 — with no radials in your yard.

Both antennas are non-resonant and use an external ATU. The difference is what each needs in the ground, and what its pattern does up the bands.

IV. Legacy Verticals

VDA vs. Cushcraft R9 & Butternut AV680

The Cushcraft R9 and Butternut AV680 are respected legacy designs that built the hobby. Both are trap-loaded resonant verticals — made resonant on specific bands with traps and loading coils. The tradeoff: each trap is a loss element. Near each trap frequency, part of your transmit power becomes heat rather than RF, and on the lower bands the loss adds up across stages.

The Greyline VDA has no traps, no coils, and no resonating elements. It is a full-length radiator from feedpoint to tip, and an external ATU handles the multiband matching instead.

The same design logic applies across the legacy field — many trap verticals share the trap-and-coil architecture and its losses. The R9 and AV680 modeled here are simply the most-requested head-to-head.

EZNEC Comparison: Greyline 20–28 ft VDA vs. Cushcraft R9 & Butternut AV680

Modeled over average ground. Key: 80M–red | 40M–blue | 20M–green | 15M–orange

Note the lower takeoff angle on the Greyline plots. Lower angle = more signal toward the horizon = more DX. The R9 and AV680 patterns — particularly on 20 and 15M — show higher radiation angles that favor regional contacts over DX.

This comparison is not apples-to-apples in the strictest sense — the heights differ, and physics is height-dependent. The point is design philosophy: a full-length, no-trap VDA produces a lower takeoff angle than trap-loaded designs at comparable heights.

16’ Greyline DXF Flagpole Antenna — Hawaii. Curb appeal, HOA approved, every band.

Real-World Propagation Data

20' DXF — Heard Worldwide on FT8

PSKreporter map from a single FT8 session — WC0R, Colorado HOA, 20' DX Flagpole. September 11, 2020. No special conditions. Marginal solar flux. Standard installation on a concrete foundation.

WC0R · 20' DXF · Colorado HOA · FT8 · September 2020. Received across North America, Europe, South America, and the Pacific.

Full operator report →

V. Height Selection

Where Each Height Earns Its Bonus

Every height works every band, 160 through 6. Height adds aperture — more signal on 40, 80, and 160 — and moves the bonus gain down the dial. The 9-foot whip adds nine feet of aperture to any height. Choose by your lot, your wind, and your low-band ambitions.

The antennas modeled here: DX Flagpoles, DX Verticals, the Skyline Series, and antenna + tuner systems.

Ham Radio is fun again! Pass it on… 73, Jon KL2A