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1/4 wavelength vertical monopole

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MainVHF/UHF Radio Resource CenterVHF/UHF Antennas1/4 wavelength vertical monopole

Este artículo también está disponible en Español (this article is also available in Spanish).


MMANA-GAL simulation of a 1/4 wavelenght monopole designed for a central frequency of 146 MHz. The following results are shown: standing wave ratio, radiation pattern and antenna input impedance.

Article first published on 10/12/2009.


Type: Monopole
Design: REMER
Impedance: 58 + j17
Simulation: MMANA-GAL Band: 2 meters

Remarks: 4 radials layout at 45 degrees. Simulation at 7 meters over perfect ground.


1. Antenna design.

Fig.1. 1/4 wavelength monopole(Vademecum REMER)


Fig.2. 1/4 wavelength monopole modeled in MMANA-GAL


File download:
VHF - Dipolo L4 146 MHz radiales a 45º.maa

Simulation report (Z, SWR, Gain):

The antenna is made of a quarter-wavelength monopole for 146 MHz, plus a ground plane made of 4 radials separated 90 degrees between them and bent 45 degrees from the monopole.


2. Standing wave ratio (SWR).


Fig.3. SWR of the monopole simulated in MMANA-GAL

The fig.3 shows a plot of the SWR for a characteristic impedance of 50 ohms. The SWR at the central frequency (146 MHz) is 1,4.


3. Radiation pattern.


Fig.4. Radiation pattern of the monopole simulated in MMANA-GAL


The fig.4 shows the radiation pattern resulting from the simulation. The antenna is omnidirectional with a gain of 7,91 dBi.


4. Input impedance.

Fig.5. Input impedance of the monopole simulated in MMANA-GAL


The fig.5 shows the input impedance of the antenna, computed with MMANA-GAL between 144 MHz and 148 MHz. The input antenna impedance at the central frequency (146 MHz) is 58 + j17 ohms.


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Ismael Pellejero - EA4FSI
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