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Old 29th Mar 2019, 6:48 pm   #8
Granitehill
Tetrode
 
Join Date: Mar 2019
Location: York, North Yorkshire, UK.
Posts: 95
Default Re: BT microwave network history

Line of sight was most certainly lost on occasion by "Snow in the dish". Ordinary snow would have little effect other than a modest fade at 6GHz, but a certain variety of wet, sticky snow could build up a wedge shaped snowdrift on the face of the dish which would cause the beam to develop a squint and to lose alignment. I've watched the AGC levels gradually fall until the link became unusable. There were protection channels, but they were multiplexed into the same system, and would fail as well. (cue lots of red lights and alarm bells !)
The snow would eventually slip down and off the dish, and the AGC levels on all receivers sharing the aerial would abruptly jump back to normal.

I understand this was one of the reasons why many of the open-faced dishes were later replaced by covered face "Low sidelobe" ones.

John
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