The VP2E Antenna: What It Is, How It Works, and How It Compares
The VP2E Antenna: What It Is, How It Works, and How It Compares
The VP2E is an off-centre-fed full-wave wire arranged as a low inverted-V. It can combine a useful vertical field component, azimuth directivity and one main mast—but its gain, polarization and elevation pattern belong to the installed geometry, not to the antenna’s name.
I like the VP2E because it asks one mast to do clever geometric work. I do not like giving it a fixed number of decibels or degrees without the model file, ground parameters and measurement plane. It sits in a genuinely useful design space between a radial-dependent quarter-wave vertical and a two-support half-square, but that is a construction comparison—not a guaranteed performance ranking.
The Historical VP2E Is One Continuous Radiator
Fritz Demuth, HB9SL, published the design as the “Low Band Vertical VP2E,” expanding the name as “Vertical Polarized 2 Element.” Electrically, however, the familiar form is not a driven element plus a separate parasitic element. It is one continuous wire close to a wavelength long, bent into a shallow inverted-V and fed away from its centre.
The classic proportions are valuable starting geometry, not a universal cutting schedule. Wavelength in the installed wire changes with conductor diameter, insulation, bends and nearby material. The feed resistance and reactance move with the exact feed position, apex angle, end height, soil and surrounding conductors. Scale the published drawing for a first model, then trim against complex impedance measured at a declared feedpoint plane.
“One support” also needs honest wording. The VP2E can use one main apex mast, but the two low ends still need anchors and safe clearance, and the off-centre feedpoint needs mechanical support plus a controlled feedline route. Its footprint is much wider than a ground-mounted vertical’s radiator, even when it avoids a circular radial field.
Current Distribution Explains More Than the Label
A wire near one wavelength supports more than one current maximum. Bending it and moving the feedpoint change how those current regions contribute in phase and magnitude to the far field. That is the useful physical picture behind the VP2E: several portions of one driven conductor contribute, and the sloping geometry changes how their fields add by azimuth and elevation.
The off-centre feed is chosen to reach a practical impedance region in the intended shape. It does not force 50 Ω, and it does not establish one transformer ratio for every installation. Measure R + jX at the antenna terminals across the operating band. Select any matching network from that measured locus, then include its insertion loss, voltage, current and thermal limits in the power budget.
The feedpoint still has two radiator terminals. Off-centre geometry alone neither proves nor disproves current balance. The wanted line mode has equal and opposite conductor currents; exterior coax current is a separate common-mode path involving the feedline, mast, station wiring and nearby objects. If coax is used, choose common-mode impedance and placement from measured outside-shield current over the required band. A generic “1:1 choke” label is not a qualification.
“Vertically Polarized” Is a Useful Clue, Not a Scalar Promise
Each sloping section contributes electric-field components set by its current, orientation and phase. Their vector sum can produce a substantial vertical component in useful directions, which explains the historical name. The same structure can also produce horizontal and cross-polarized components. The ratio varies with azimuth, elevation, apex angle, wire height and environmental coupling.
Pattern language needs the same discipline. A low inverted-V over real earth can show directional azimuth lobes and useful low-elevation radiation, but no fixed takeoff angle belongs to every VP2E. Height in wavelengths, the shape of the wire, soil conductivity and permittivity, terrain, end clearance and unintended feedline radiation all move the lobes and nulls.
Ground reflection and loss are part of that pattern. ITU-R P.527 provides representative electrical characteristics for earth materials, not one “average ground” that describes every field, beach or garden. Use measured local values when available and run a range of credible conductivity and permittivity values when they are not.
No Radial Field Does Not Mean No Ground Effect
A VP2E is a two-terminal wire radiator, so it does not require the galvanically connected radial or counterpoise system that completes a ground-mounted quarter-wave monopole. That is a real installation advantage. It does not make the antenna independent of earth.
The low wire ends couple capacitively to the soil and nearby objects. Real ground affects terminal impedance, loss and the reflected field that shapes the elevation pattern. Wet soil, dry rock, vegetation, fences and buildings can change an installation even though none is wired to the feedpoint. A low end can also carry substantial RF voltage depending on frequency and current distribution, so keep every conductor and anchor inaccessible during transmission and apply the site’s RF-exposure, lightning, structural and electrical-safety controls.
Compare the VP2E, Vertical and Half-Square at the Same Boundary
A fair comparison holds frequency, terrain, soil, conductor loss, available supports and accepted antenna power constant. It also distinguishes directivity, gain and realised gain. Quoting transmitter forward power for one antenna and accepted feedpoint power for another hides feedline, matching and mismatch losses.
| Question | Quarter-wave vertical | VP2E | Half-square |
|---|---|---|---|
| Driven geometry | One near-quarter-wave vertical conductor plus a radial, counterpoise or ground-return system | One near-full-wave wire, off-centre-fed and folded into a low inverted-V | Two near-quarter-wave vertical legs joined by a near-half-wave horizontal wire |
| Typical support problem | One vertical support plus the radial footprint and feed-base hardware | One main apex support plus two end anchors and an off-centre feed support | Two elevated supports plus anchors and feed hardware |
| Azimuth behaviour | Near-omnidirectional only when the radiator, return system and surroundings are sufficiently symmetric | Directional lobes depend on inverted-V geometry, height, ground and common mode | Broadside behaviour depends on leg currents, spacing, height, ground and feed arrangement |
| Ground dependency | Return-system loss and soil materially affect efficiency and pattern | No connected radial field, but earth still affects impedance, loss and pattern | No monopole radial field, but the low vertical legs and reflected field still interact with earth |
| Polarization | Predominantly vertical in an ideal symmetric installation | A geometry-dependent vector mixture, often with a substantial vertical component in selected directions | A geometry-dependent field commonly dominated by the vertical legs in broadside directions |
That table deliberately contains no winner. A well-built vertical over an effective return system may outperform a compromised VP2E in a required direction. A half-square may provide a stronger broadside result when its two supports, feed arrangement and site are favourable. The VP2E may be the best engineering choice when one high apex, two low anchors and no radial field fit the site. The answer comes from the required coverage and declared constraints.
Model the Installation, Not a Stick Figure
NEC is well suited to thin-wire investigations within its modelling limits, but its output is conditional on the input deck. Record enough detail for another operator to reproduce the comparison:
- frequency, wire coordinates, apex angle, end height, conductor radius and any insulation treatment;
- segment length, segmentation-convergence checks and the exact excitation segment;
- ground model, conductivity, relative permittivity and any terrain limitation;
- wire and network loss, feedline route, mast, nearby conductors and the common-mode boundary;
- terminal impedance reference plane and accepted power; and
- whether the reported quantity is directivity, gain or realised gain, with its azimuth, elevation and polarization.
Run the VP2E, quarter-wave vertical and half-square over the same ground and at the same accepted power. Use the supports and end heights the site can actually provide. Sweep plausible soil values and construction tolerances instead of presenting one run as a law. NEC assumes declared geometry and ground; it cannot know about the fence, damp rope, buried services or feedline that was omitted.
Correlate the Model With the Installed Antenna
Start with a calibrated VNA measurement of complex impedance. Measure at the feedpoint or de-embed a characterized feedline so the reference plane is explicit. Keep R, X and SWR across the band; a low shack-end SWR alone cannot separate antenna impedance from line transformation and loss.
Then measure common-mode current on the outside of the coax, mast and other plausible return paths at repeatable positions. Change one feedline route or choking condition at a time and repeat A/B/A. If the terminal impedance or field pattern moves, that path belongs in the installed antenna model.
For a pattern or gain comparison, switch rapidly among antennas at the same site, frequency and accepted power. Keep receiver bandwidth, gain state, detector and timing fixed. A stable beacon or controlled distant transmitter is better than unrelated contacts through changing propagation. Record azimuth, distance, polarization and uncertainty; one S-unit report in one direction is not a gain measurement.
The most informative result is a small correlation table: predicted and measured R + jX, modelled and observed lobe direction, outside-shield current before and after control, and relative field against the same reference antenna. Disagreement is useful—it identifies omitted ground, feedline, mast or environmental coupling.
Where the VP2E Earns Its Place
The VP2E remains clever because its construction trade is distinctive. It uses a near-full-wave wire and one main apex to create a pattern that can favour selected azimuths and low elevations without a connected radial field. It can be an excellent answer when the site permits two low anchors but not two tall supports or a large radial system.
That is enough of a claim. It does not need a universal gain advantage, one launch angle or a promise to beat a low dipole, a vertical or a half-square. Preserve the geometry, model the real site, measure the complete current path and let the installed evidence choose the antenna.
Bottom line: the VP2E is an off-centre-fed full-wave inverted-V with a useful historical design logic. Treat its polarization, pattern, impedance and comparative performance as model-and-measurement results tied to the actual height, ground, feed system and surroundings.
Primary and authoritative references
- Fritz Demuth, HB9SL — “Low Band Vertical VP2E,” Old Man, October 1993
- IEEE 145-2025 — Standard definitions of terms for antennas
- ITU-R P.527-4 — Electrical characteristics of the surface of the Earth
- NTIA — Numerical Electromagnetic Code capabilities and model limitations
- NIST/NPL — Antenna measurement challenges, feed effects and uncertainty
- Keysight — Impedance Measurement Handbook
- Keysight — Reference-plane extension and de-embedding
- ARRL — RF ground and quarter-wave vertical return-system boundaries
- IEEE EMC Society — Differential- and common-mode current
Mini-FAQ
- What is a VP2E antenna? It is a near-full-wave continuous wire arranged as a low inverted-V and fed off-centre. The historical name expands to “Vertical Polarized 2 Element,” but it is not a conventional driven-plus-parasitic two-element array.
- Does a VP2E require radials? It does not require the connected radial system of a ground-mounted monopole because it has two radiator terminals. Earth still affects its impedance, loss and radiation pattern.
- Is the VP2E always vertically polarized? No. Its sloping wire sections produce a vector mixture whose vertical, horizontal and cross-polarized components vary with direction, geometry, height, ground and surroundings.
- Does the VP2E have a fixed takeoff angle or gain? No. Those results depend on electrical height, wire shape, soil, terrain, loss, feedline current and the stated gain definition. Quote them only with a reproducible model or measurement.
- Is a 1:1 choke always required at the feedpoint? Not as a universal rule. Measure outside-shield current and choose any common-mode control by frequency, placement, impedance, voltage, current and thermal limits.
- How should I compare a VP2E with a vertical or half-square? Model and rapidly measure them over the same ground, at the same frequency and accepted power, with declared supports, feed losses, reference planes and uncertainty.