So far, we have talked about using packet, VHF/UHF frequencies and utilizing repeaters to communicate between communities that are relatively close to one another. There is a simpler and less expensive alternative that would not require elaborate antenna systems and repeater systems that could be utilized for communities, say, two or three times the distance of the horizon (horizon distance is about 20 miles).
That is to use HF transceivers at low frequencies of 1.5 to 4 MHz. At these frequencies there is almost always a secondary propagation called ground wave. That is, the signal follows the curvature of the earth for some distance. These signals could also be voice, CW, or digital.
The primary disadvantage of this mode is that interference and noise is frequently caused by lightening from thunderstorms. Today, pre pole shift, this noise can be extreme because a thunderstorm hundreds of miles away causes noise signals that are propagated via the upper atmosphere. Post pole shift, that mode of propagation would probably be gone, at least for quite a while, and we would only be interfered with by local thunderstorms (lightening). In any case, using modern radios with DSP (digital signal processing) to filter out the noise, and by using digital (Internet-like) communication modes that keep repeating the packet until it is received properly and acknowledged, this relatively close intercommunication would be quite reliable.
Offered by Ron.
WB5KAN - General Class