TITLE:
Radio Wave Propagation Experiment in Sugarcane Fire Environments
AUTHORS:
Douglas Letsholathebe, Kgakgamatso M. Mphale, Samuel Chimidza, Malcolm L. Heron
KEYWORDS:
Canefire, Radiowave Loss, Attenuation, Thermal Ionization
JOURNAL NAME:
Journal of Electromagnetic Analysis and Applications,
Vol.8 No.7,
July
21,
2016
ABSTRACT: Large fires have an effect of suppressing Very or Ultra High Frequency
(VHF/UHF) radio wave signals strength which consequently impact negatively on
the efficiency of radio communications at the frequency ranges. Mobile
hand-held radio operating at the frequency ranges is a major communication tool
during fire suppression; therefore inefficient radio communication systems put
lives of fire fighters at risk. One of the causes of signal attenuation in fire
environment is plume ionization. Plume species which include graphitic carbon,
alkalis and thermally excited radicals such as methyl are responsible for
ionization. As atmospheric pressure ionized medium (combustion plasma),
sugarcane fire has momentum transfer electron-neutral collision frequency much
higher than plasma frequency, hence propagation of VHF/UHF radio waves through
such a medium is predicted to suffer a significant attenuation and phase shift.
Radiowave propagation measurements were carried out in a moderate intensity
prescribed sugarcane fire at 151 MHz frequency over a 590 m path using a
radiowave interferometer. The radio wave interferometer measured signal
attenuation of 0.43 dB through the fire with maximum temperature and flame depth
of 1154 K and 8.7 m, respectively.