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+--- Thread: Does smoke haze affect VHF/UHF propagation? (/thread-893.html)
Does smoke haze affect VHF/UHF propagation? - VK4WDM - 22-11-2019
The atmosphere over much of eastern (and probably southern and western) Australia have been filled with smoke haze for weeks now. My question is: does smoke haze inhibit propagation on VHF and UHF?
I am quite active on the AO-91 and AO-92 satellites and I have noticed that signal strengths from the birds when I am working them whilst they are over southern Australian, where the signal is traveling at a low angle and is traversing the smoky atmosphere for quite a long time, are much weaker and more unstable than usual.
By contrast, the signals I am hearing from the bird when it is north of me and at the same distance and angle, but presumably less atmospheric smoke, have their usual signal strength and stability.
Any other sat ops, or terrestrial ops, notice the same thing?
73
Wayne VK4WDM
RE: Does smoke haze affect VHF/UHF propagation? - VK2KRR - 23-11-2019
Hi Wayne
I dont know what frequency your working on there, but smoke probably has some effect of diffraction and scattering due to the differing densities of the smoke compared to normal troposphere, becoming greater as the frequency increases, to a point where it would almost completely be scattered or reflected at microwave frequencies.
BoM rain radars can plot smoke on the rain radar screen when its severe enough and thus must be a reflection of the signal back to the receiver.
RE: Does smoke haze affect VHF/UHF propagation? - VK4WDM - 23-11-2019
(23-11-2019, 11:05 AM)VK2KRR Wrote: Hi Wayne
I dont know what frequency your working on there, but smoke probably has some effect of diffraction and scattering due to the differing densities of the smoke compared to normal troposphere, becoming greater as the frequency increases, to a point where it would almost completely be scattered or reflected at microwave frequencies.
BoM rain radars can plot smoke on the rain radar screen when its severe enough and thus must be a reflection of the signal back to the receiver.
Hello Leigh
The down-links from the satellites are 145 MHz and the up-links are 435 MHz. They are in low orbit and I often work them when they are only 2 degrees or so above the horizon ( south coast of VK5 for instance) so the signals are traveling a long way through smoky atmosphere to get to and from the satellite.
Wayne VK4WDM