Hellschreiber (Feld-Hell)

Hellschreiber, a 70-year-old mode halfway between CW and fax, is German for "shiny writing." It's also a play on the name of its inventor, Dr. Hell. What we see here is Feld-Hell, "Field Hell," which was used a lot in World War II (war is Hell?). The original version sent typed characters as CW pulses. These represented pixels of a chosen font, as scanned vertically onto a moving paper tape in the receiver. Today, a computer program simulates the moving tape, and the pulses are usually a keyed, 980-Hz, quasi-synchronous, audio tone from a sound card fed to a single-sideband transmitter. Everything else is pretty much the same.

Why bother with this old mode? Because it's fuzzy. It allows shades of grey in the output, which gets increasingly lighter as the signal grows weaker. It's read by eye, allowing the human brain to fill in characters that would barf a computer. This locally-generated signal looks like Hell in more ways than one, but Hell received from the air tends to look pretty clean except for the inevitable keying clicks. Hams are raising Hell because it's great for DX, it does well with computer DSP, and it's just good, strange fun.