I found this mode on my internet travels. The history behind it is very interesting.
"Feld-Hell
means "Field" Hellschreiber, or "bright writing".
It was invented in 1929 by Rudolf Hell, as the
earliest widely used method of transmitting text by facsimile.
Each character is defined to have a 7 x 7 matrix
of dots, including space before, after, above and below the
character. Each dot is transmitted in a strictly
timed sequence using on-off keying of a carrier or subcarrier.
Each character takes 400 ms to send, thus a
throughput of 2.5 characters/sec or 25 WPM is achieved.
The signal is like high speed CW, with a
similar narrow bandwidth. Feld-Hell is spectrum and power
efficient, and is extremely resistant to noise because being
directly human readable, noise dots are rejected
and the letters recognized in context. (Text is still
recognizable when 20% of the data bits are in error -
RTTY gives up completely at 5%). Feld-Hell is prone to carrier
interference exactly on frequency, and
suffers from temporary errors due to fast fades. Because there is
no synchronism, noise does not affect the
interpretation of characters. Timing accuracy need only be better
than 5%, and lack of synchronism is
compensated for by printing the text twice, one line above the
other. Feld-Hell has a significant following on
HF, where use of modern software and DSP techniques have raised
its performance and popularity."
Info taken from Nino's web site
The latest Windows 95 and Sound Card software from Nino IZ8BLY. The software is very sensitive, fully "fuzzy", offers a wide range of speeds, DX mode, choice of colours, a choice of Windows fonts, and a choice of excellent FIR filters, down to 100 Hz wide. It even transmits and receives FSK-Hell and CW and includes a waterfall plot for easy tuning! Check the IZ8BLY Web Site for the latest version and information. If you find it difficult to access Nino's site Version 3.1 (700k) is here. You need a powerful PC - a PentiumTM or better.
You can download it here