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  #1  
Old 06-17-2004, 09:42 AM
Thato
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Hi Guys,

Does anyone know the effect of the presence of excessive smog/pollution on Microwave links. Will this also vary based on the frequency band used?
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  #2  
Old 07-23-2004, 12:25 AM
Harvey Lehpamer Harvey Lehpamer is offline
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In my 20 years plus of dealing with MW links I have never used or had a need to use this piece of information.
Smog, polution and fog are important in designing optical links but not microwave links.
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  #3  
Old 07-23-2004, 07:45 AM
Thato
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Default Industrial Smog

There is a natural phenomenon called Hamadan, which is a thick mist of dust and most probably pollution which causes chaos on the networks in Nigeria.
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Old 08-11-2004, 08:44 PM
Peter C Peter C is offline
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I've never heard of this either, but then in New Zealand we've got fairly clear air.

What I would do to ensure links never fail due to this phenomenom (if it is in fact the dust particles causing absorption or diffusion) is to log the signal level (fade margin) on several links for a long period (months if possible).

If fades (link degradation) correlate with the dust then you will be able to determine how much additional fade margin is required to overcome the dust.

If fades don't correlate with the dust then it's some other factor and the simple answer is the link hasn't been designed with enough margin and/or diversity.

The long duration of analysis may sound like a burden, but if it solves a nationwide systemic and regular failure of comms networks it would be well worthwhile.

Peter
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Old 08-16-2004, 07:15 AM
Lars H-L Lars H-L is offline
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Default Dust storms

Smog and haze is not an issue for MW links as Harvey Lehpamer says. Dust storms on the other hand may have harmful effects.

Probably the dust storms in Nigeria are so-called haboobs made by the cold downdraught in a thunderstorm. These give rise to refractivity changes in the air mass suspending the dust; the fading during a haboob is caused by the atmospheric side effects (e.g. multipath).

Investigations have shown that the dust content per se only gives negligible propagation impairments (attenuation and depolarisation) up to say 30 GHz, even for low optical visibility.



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  #6  
Old 08-18-2004, 09:23 AM
Lars H-L Lars H-L is offline
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Default Harmattan

Harmattan (not Hamadan) is the name of a wind blowing from the sahara to the atlantic ocean passing the countries along the guinea coast. This is a wind (not storm) during the winter months, persistent for prolonged periods of time. If this common and widespread wind really "causes chaos" in the MW network you are in real trouble.
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  #7  
Old 03-16-2005, 09:36 AM
Joshua Joshua is offline
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All,

Duct entrapment and severe fading under Harmattan condition is a major microwave propagation problem in the Gulf of Guinea nations - West Africa from Nigeria to Senegal.

The main cause is temperature inversion. Considering the cool air from Europe over hot ground.

We need more information on this though. Anyone with any?
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