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Jon -

That would be an HF (High Frequency) radio.

An HF antenna would be required for long range communications. These HF frequencies are between 3 and 30 MhZ. Owing to the fairly low frequencies utilized, the antenna must be physically fairly long. For example, a quarter wave antenna on 3 MhZ would be about 64 feet long. On 7 MhZ, about 32 feet, and on 30 MhZ about 8.5 feet or so. Be advised that for reliable communication, the frequency utilized must go down as the sun drops below the horizon and the ionosphere thins and rises. Reliable communications over about 1000 to 2000 miles and beyond would be realized in the 7 to 14 MhZ band - 40 to 20 meters. Skip would have to be managed (you don't want to send the signal OVER and past the receiver you need). Frequent frequency adjustments would be needed as you moved away and toward a reciever and the time of day changed, as well as the changes in latitudes. It would also be dependent upon the season. This wire antenna would be attached to a transmitter, and could be reeled in or out with RF (radio frequency) traps in the wire to help keep it tuned, and a weight (called a "fish") to the end of it to keep it straight and prevent kinking.

Power can be fairly low - sometimes as low as 10 watts or so, but in order to overcome any interference from solar activiry, it should ideally be about 100 watts or more. Also, a good ground is ESSENTIAL to ensure adequate radiation.

Higher frequencies - the VHF spectrum and above - are not as susceptable to ionospheric skip as HF, MF, LF and VLF - rather, they are line of sight the higher in frequency you go, although there are a number of atomospheric conditions that can cause a "tunnelling" effect or "ducting". Lower frequencies are more subject to absorbtion.

There are other factors to consider - directionality, radiation pattern changes as the wire rises and/or lowers due to changes in airspeed, frequency changes as the antenna waves in the breeze if there is too much coupling between the master oscillator and antenna (although this is rare but noit unheard of in modern design)... on and on.

In short, there is a fair amount of training that ya have to familiarize yourself with when utilizing HF for long range communications. Time of day, weather.... a number of oddities.

HF is still used, but is being supplanted by satellites. Still, it's reliable, fairly simple, doesn't require much complexity in the way of equipment, and does the job.