For that reason: cheap available quartz crystals, since the 1970s, the shortwave radio frequency 3.579Mhz has been a spot on the dial where radio hams use low p

For that reason: cheap available quartz crystals, since the 1970s, the shortwave radio frequency 3.579Mhz has been a spot on the dial where radio hams use low power home made morse code transmitters. At night, a range of a couple of hundred files is usually possible.