Amateur Radio Campaign and Award „125RH“
To mark the 125th anniversary of the birth of Dr.-Ing. Rudolf Hell (19 December 1901 – 2002), technology enthusiasts are celebrating the life’s work of one of Germany’s most significant inventors. Known as the ‘Edison of the printing industry’, he revolutionised newspaper printing with the fax and the Klischograph. Among amateur radio operators, he remains unforgettable above all for one ingenious masterpiece: the Hell transmission method (also known as Hell writing or Feldhell).
What is the ‘Hell’ transmission mode?
Patented in 1929, this method operates on an image-based rather than a code-based principle. Unlike modern digital modes, Hell does not convert characters into binary code. A letter is scanned in a raster pattern and transmitted as a simple ‘signal/no signal’. At the receiver, this signal is plotted directly as pixelated text onto a paper tape (or, nowadays, onto a screen).
Why the system is so ingenious
- Human error correction: Because an image is transmitted, radio interference does not result in incorrect characters (as with RTTY or FT8), but only in visual blurring. The human eye can usually still read the noisy text with ease.
- The diagonal printing trick: To compensate for synchronisation fluctuations, the text is printed twice, one line below the other, by default. This ensures that at least one line is always perfectly legible.
Its significance in amateur radio today
Although it has long since been superseded in the commercial sector, Feld-Hell is more alive than ever in amateur radio as a digital mode (via sound card and software such as Fldigi):
- Extremely robust: Ideal for long-distance contacts (DX) under difficult conditions and with minimal transmit power (QRP).
- Narrowband: With a bandwidth of only around 245 Hz, it takes up very little space on the shortwave bands.
- The fascination of nostalgia: It combines the mechanical pioneering era of communications technology with modern software.
Every time a text appears on the screen today, emerging directly from the static of the shortwave, the genius of Rudolf Hell lives on.