Building Microwave Networks Part 1

Some Thoughts looking back 30+years

Early 1980's - Rebuild 6 GHz Analog 600 channel FDM Microwave systems

Path Surveys and Profiles were primarily done with paper topo maps, land surveyors/sextant positioning for critical points, and profile chart graph paper on D size paper constructed by hand. Just started using scientific calculators

Concerns were fade margin, and 4 Khz channel noise over a 600 channel Frequency Division Multiplexed baseband signal. In the electric Utility Industry, high speed relaying was the killer 'app' and the fast channels were on specialized baseband Modems that operated in 60 Khz chunks of the baseband and made by Motorola - MC22 was the model. The new stuff was GE type 10 tone relaying in 4 Khz voice band channels. Transfer Trip schemes were in the sub 4 millisecond timing range for MC22 and sub 10 millisecond for the Type 10 channels.

The FDM based band had to be 'broken' up every 10 hops or so (sometimes less) due to Noise Power Ratio additive noise in the 4 KHz channels in part of the baseband. the entire baseband had to be demuxed and reinserted using analog FDM coaxial and voice band cross connects.

In the 1980's the conversion was from reflector based antenna systems to the 'new' waveguide based parabolic dish systems. Towers had to be rebuilt or replaced to accommodate the increased loading. The reflector based system had a dish on the ground with a short rigid waveguide system from the shelter and radiated a tower top flat panel reflector that was angled to reflect the signal to the far end.

Next topic - Conversion from analog to digital T1 and sonet based systems