EA4FSI
HF · ANTENNAS · SIMULATION

Marconi Antenna

This article describes the characteristics of the Marconi antenna and shows the results of several simulations made with MMANA-GAL, covering models optimized for the 20 m, 40 m and 80 m bands. The goal of the simulations is to check the behaviour of the antenna both in it fundamental band of design and in the harmonic bands, taking into account the impedance and the radiation patterns.

HF · MARCONIMMANA-GAL
Marconi Antenna
Marconi
TypeVertical wire antenna
DesignREMER
Impedance50 Ω
SimulationMMANA-GAL
BandMultiband
Remarks: Antenna length (m) = 71.25 / f (MHz)
Marconi for 20 mMarconi_20m.maaMarconi for 40 mMarconi_40m.maaMarconi for 80 mMarconi_80m.maaMarconi antenna for 20 m — Simulation report (PDF)Marconi_report.pdf

1. Antenna design and modeling

Figure 1 shows the Marconi antenna modeled in MMANA-GAL, oriented along the Z-axis.

Marconi antenna model in MMANA-GAL.
Fig. 1. Marconi antenna model in MMANA-GAL.

The Marconi antenna consists of a vertical wire approximately one-quarter of the operating wavelength long, fed at its lower end. It requires a highly conductive ground plane. The Marconi radiator is resonant at odd multiples of a quarter wavelength. The wire length is calculated as L (m) = 71.25 / f (MHz).

2. Simulation results

This section presents the MMANA-GAL simulation results, including the calculated standing-wave ratios (SWR) and radiation patterns for each frequency band.

2.1 Standing-wave ratio (SWR)

This section presents the simulated SWR at 7 MHz and 21 MHz (the third harmonic) for a Marconi antenna designed for the 40-metre band.

Figure 2 shows the SWR in the design band (7 MHz).

SWR of the Marconi antenna in the design band (7 MHz).
Fig. 2. SWR of the Marconi antenna in the design band (7 MHz).

Figure 3 shows the SWR in the third-harmonic band (21 MHz). For SWR < 2, the antenna has a bandwidth of approximately 310 kHz at this harmonic.

SWR of the Marconi antenna in the third-harmonic band (21 MHz).
Fig. 3. SWR of the Marconi antenna in the third-harmonic band (21 MHz).

2.2 Radiation patterns

This section presents the simulated radiation patterns at 7 MHz and 21 MHz (the third harmonic) for a Marconi antenna designed for the 40-metre band.

Figure 4 shows the radiation pattern in the design band (7 MHz).

Radiation pattern of the Marconi antenna in the design band (7 MHz).
Fig. 4. Radiation pattern of the Marconi antenna in the design band (7 MHz).

Figure 5 shows the radiation pattern in the third-harmonic band (21 MHz).

Radiation pattern of the Marconi antenna in the third-harmonic band (21 MHz).
Fig. 5. Radiation pattern of the Marconi antenna in the third-harmonic band (21 MHz).

As a vertical antenna, it is not suitable for NVIS operation. At the design frequency, its radiation pattern is omnidirectional, with a gain of approximately 5.13 dBi. At odd harmonics, the elevation pattern becomes distorted and may develop two main lobes, with reduced gain.

ORIGINAL PUBLICATIONSEPTEMBER 2008