Radio Wave Propagation Experiment in Sugarcane Fire Environments

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.

Microwaves propagation through a small fire curtain at 3.55 GHz and 6.26 GHz and the impact on vital signs detection by using a four-element patch antenna array

“…The enhancement was explained by diffraction phenomena which contributes to the IOP Publishing doi:10.1088/1757-899X/1254/1/012010 2 recovery of the signal. The frequency range (100-180) MHz presented attenuations of (3)(4)(5)(6) dB in outdoor small fires, while the (400-450) MHz range showed an attenuation of (10)(11)(12)(13)(14)(15) dB for the same fire geometry and structure. It was also underlined the role the turbulences of fire have on the apparition of Doppler spread effects of the signals.…”

“…Values of (0.35 -0.9) dB attenuation were emphasized in this frequency range. Later in 2016 the same authors [12] carried out measurements at 151 MHz over a 590 m path in a moderate intensity fire and found a signal attenuation of 0.43 dB. In [13] the behaviour of the frequency range (350-400) MHz at thru-fire propagation when different fuel types were used was investigated.…”

Microwave spectra inside the combustion chamber of a kraft recovery boiler – effects on communications

“…For low frequencies (< 6 THz), the Rayleigh-Jeans approximation is based on the approximation [15] e (h f /kT) ≃ 1 + kT h f (2) So the Rayleigh-Jeans approximation can be modified to the form…”

“…The main mechanism for charged ions and free electron generation is chemi-ionisation rather than thermal ionisation. Ionisation is considered an important factor for both attenuation of radio and microwaves and generation of radio and microwave spectra [13][14][15][16].…”

Effects of Fire Plumes From Pine Needles on Small-Scale Fading in Radiowave Propagation

“…Radiowave propagation in vegetation media and its experimental excess loss assessment under fire conditions, is a rather important topic when communication reliability is at stake, particularly in remote rural areas when affected by severe wildfires. In events in which fire spreading gets out of control, emergency radio communications, that are usually employed to aid fire suppression operations, should provide the required resilience for effective disaster relief operations [1]. While the topic of radiowave propagation in vegetation has been extensively studied in the literature [2]- [6], the effect of fire on top of the attenuation caused by vegetations lacks more research.…”