Welcome to the World of Fuzzy Modes!
| Hell Modes | Philosophy | Feld-Hell | MT-Hell |
Radio communications, like most things in this world, would appear to come in two forms, analogue and digital. Analogue refers to things that have smoothly varying properties that are not easily expressed in numbers, for example human speech, time read from a clock with moving hands,and almost all natural processes from the fluttering of leaves in the wind to the silvery trails left by a snail. Digital refers to things that can be defined in steps - on and off, pass and fail, stop and go, up and down, day and night, integer numbers.Our radio spectrum is filled with signals both analogue and digital in nature. Broadcast radio, TV, SSB transmissions and noise, both man-made and natural, are analog transmissions; while radio teletype (RTTY), PSK31, packet radio, cellular phones and a whole range of data communication, radio control and telemetry applications involve digital transmissions.
These days digital is considered trendy - computers, TV, CD and MP3 music, telephones, clocks - but humans are not digital animals.All our senses - feel, sight, smell, taste and sound, are analogue in nature. Consequently we do not relate easily to the digital world. So welcome to the world of
Modes!
By the way - Morse may be considered a
Most digital communications modes are intended to be read by a machine, be it mechanical or electronic. Conversely, analogue modes are generally intended for direct human interaction. There are however a very few machine generated communication modes intended to be human readable. These are (to my knowledge), Morse, FAX, SSTV, Feld-Hell and MT-Hell, although they are not all necessarily trulyHellschreiber describes a method of sending text by radio or telephone line that involves dividing each text character into little pieces and sending them digitally. Hellschreiber is a German name, meaning "bright writing", or "clear writing", and may be a pun on the name of the inventor, Rudolf Hell, who patented Hellschreiber in 1929.
The first major application of Hellschreiber was transmission of text for newspapers by telephone line in the years beforeWorld War II. Hell's invention was thus the world's first widely used and practical facsimile machine.War-time machines were more portable, and intended for use with field telephones and radio equipment.Later, Hell page printers were developed.
The traditional method of sending Hellschreiber is to key a Morse-type (CW) transmitter ON for every black spot in a text character,and OFF for every white place. Different parts of each character are sent at different times. The technique is still in use by interested Amateurs, still using pre-war parameters, communicating world-wide. This mode is now called Feld-Hell (Field-Hell), since it was originally used for field communications by the German Army. Feld-Hell offered good immunity to interference and provideda clandestine transmission capability because nothing was transmitted until a key was pressed. Commercial variations of Feld-Hell could still be heard occasionally on HF up until the 1980s, transmitting Chinese and Korean characters. 
Print from a wartime mechanical Hellschreiber
It is also possible to transmit text information by sending the dots using some other property of the transmitter carrier, for example phase (PSK-Hell) or frequency (FSK-Hell and FM-Hell). Alternatively, different parts of each character can be sent on different frequencies. This latter technique uses the frequency domain, as opposed to the more conventional time domain. This type of transmission is known as Multi-Tone or MT-Hell. Until recently, it was thought that MT-Hell was a 1990's invention, but we now know it was described in 1937!
G3PLX working PA3BQS in Feld-Hell
Feld-Hell, PSK-Hell, FM-Hell and MT-Hell are all in use on the amateur bands. See "Operating", below. The hot DX spot is 14.071 to 14.075 MHz, ±Pactor QRM. 18 MHz is also very good - try 18.104 to 18.107 MHz. With all these modes long distance DX is practical, and worldwide contacts are now routine!Feld-Hell is especially useful in poor conditions when other modes are ineffective - especially just after a magnetic storm when the ionosphere is lively but unstable. FM-Hell is best for very weak signal DX, and is not seriously affected by the Doppler problems that limit PSK31. MT-Hell lacks sensitivity unless very slow, but is excellent on LF. MF and low HF where atmospheric noise is the limiting factor. (The picture at the top of this page is an example of Sequential MT-Hell).
The technical specifications of Feld-Hell and MT-Hell are not especially complicated, and anyone can have a copy by downloading the Hellschreiber Modes Technical Specification document (133 kB). The document does not include specifications of PSK-Hell or FM-Hell. We have to keep our competitive edge somehow! If you feel you need to know, contact IZ8BLY or ZL1BPU.
- ZL/VK: 3559 kHz at 0730 - 1030 UTC. "Hellraisers' Net" on 3560 kHz LSB (SSB, Hell and you name it!) at 8:30 pm Fridays
- Europe: 3579 kHz at 2130 UTC Tuesdays, 7037 kHz Sundays at 1200UTC, and 3579 kHz Sundays at 1530UTC.
- DX Hell: 14.071 - 14.075 MHz, 18.104 - 18.107 MHz or 21.063 - 21.070 MHz, 24 hours/day! Calling frequency 14.073 MHz carrier. USB operation is conventional (affects FM-Hell and Duplo-Hell).
DX contacts can also be arranged by email, via the Hell Reflector, or by commandeering PSK31 stations!- A Feld-Hell Contest is hosted by the DARC each October.
- A fun Hellschreiber Activity Day (multi-mode) is held about every three months. Details are posted on the Hell Reflector.
- See 'Where should I operate?' for more details.
You too can have enjoyable 10,000 km Hell contacts as easy as this!
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