Several recent posts in this thread have mentioned the "horn" microwave antennas used by AT&T Long Lines. As David Lesher noted in TD 28:127:
Those horns often carried six circuits: 4 Ghz horz > polarization, 4 Ghz vertical, 6 Ghz h & v, 11 Ghz h & v. They > delivered a jaw busting 48dB of gain at 11 Ghz, with a beam > width of about 0.75 degrees. But then they had 36 ft^2 of > throat, were 14 ft+ tall and weighed several thousand > pounds... despite being aluminum...
Narrow bandwidth not only provided substantial main lobe gain, but it reduced side lobe gain. This, in turn, reduced interference to or from other antennas, including satellite antennas.
Cable TV companies sometimes used TVROs based on the same design in order to block interference from point-to-point microwave links. Two examples:
Lyndhurst, New Jersey, 1982:
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Lamar, Colorado, 2007:
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Of course, in some situations, there was an easier way to block interference: put the antennas behind a hill or a berm. Two examples:
West Haven, Utah, 2001:
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Warwood, West Virginia, 2008:
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Neal McLain