Disclosed herein are hub-based wireless networks employing end-devices at intermediate wireless at ranges of thousands of meters, utilizing packets that include a preamble and a data payload. End-devices may be such things as keypads, door latches, occupancy monitors, sprinkler controllers and other devices controlled or monitored in a campus or a collection of buildings. A digital spread-spectrum frequency hopping rotation is used, wherein packet transmissions rotate through frequency sequences to spread radio-frequency emissions impact over a set of frequencies. A spectrum-impact-smoothed channel set is fashioned using sequences that each specify a unique preamble frequency relative to the other sequences and channels. The set is traversed as packets are transmitted, thereby distributing the focused radio-frequency emission impact of packets having long preambles over time. Detailed information on various example embodiments of the inventions are provided in the Detailed Description below, and the inventions are defined by the appended claims.