ZL1HIT Hellschreiber Page

Hellschreiber (pronounced "Hell - Shrey - Ber" [ I think ] ) is a technology invented by a German chap in 1927 for use as a reliable radio communication method. The chap's name, apparently, was Mr. Hell. There's the first clue. Now "Schreiber" translates to "Writing" or "Writer" I believe. Hence "Hell - Schreiber" - Hell Writer. Such as I understand it all anyhow.

The systems method of operation is very similar to modern day FAX machines. It is even closer still, in my opinion, to (maybe not so...) modern day "Weather FAX" radio systems. Fig 1. is a sample of what Hellschreiber looks received like over a "reasonable" radio link on the 14 MHz (20 meter) band

Fig 1. Partial screen shot of IZ8BLY Hellschreiber software

The gray bars in the background are interference signals and noise as is characteristic of the H.F. (High Frequency or "Short-wave") bands. To the ear these interfering signals were approximately half the level of the desired Hellschreiber information. This particular sample shows no evidence of "multi-pathing" or the "ghosting" effect which can be caused by such. That is another totally fascinating subject all in itself!

You can see that this mode is very tolerant of poor radio conditions. A truly remarkable invention for it's time. Today we are using fully solid state equipment for sending and received to mode of communications. namely IBM^(tm) compatible computers. It would be fascinating to construct a mechanical printer but this is more than likely way beyond my personal skills!

You may now have guessed that the original Hell Schreiber was received on a paper strip. The slight upward slant occurs because the transmitter scanning and receiver "printer" are not perfectly synchronized. To prevent huge complexity the system was designed to have the human eyes and brain take care of the synchronization errors. To do this the receiver prints each received column twice. That way we can always see at least one full letter. Today we call this type of system a "fuzzy mode" of communication. ZL1BPU appears to have coined this term and here is a definition he gives:

Transmissions must be uncoded RX equipment must not decide when there is a data bit, but simply present samples as often as possible, i.e. over sample the bit rate. RX equipment must not make decisions on the status of a data sample, i.e. black or white, but may present the data bit according to a probability of it being black or white by using a grey scale to epresent probability. The aim of course is to present exactly what is on the radio channel for the eye/brain to decode - exactly like CW, which is another fuzzy mode.

The actual sample shown above was transmitted using a PIC16F84 Microcontroller based beacon which I designed and programmed with help from Murray, ZL1BPU. The circuit comprises a single IC, 3 capacitors, 2 resistors, 1 quartz crystal and 1 transistor. The singe IC is the PIC Microcontroller. This is yet another example of how powerful modern electronics is getting for the home hobbyist. Full details of the ZL1HIT Hellschreiber Beacon Project can be found HERE.

[ Details of how you can build your own PIC Micro' programmer and where you can get excellent FREE software to drive it can be found at http://www.conquestsys.com/picprog/ ]

For a complete and thorough description of the new/old Hellschreiber fuzzy technology please start with ZL1BPU's (Murray) site. CLICK HERE. Murray has been encouraging the use of and dissemination. There are links there to Nino's (IZ8BLY) home site. Nino's Hellschreiber software is fast becoming the best available software for MS-Windows 95/98 computers with sound card. Murray has also had a lot to do with this developement. There are many other interested and involved parties so for goodness sake do not take this list as anything like complete!

Page updated April 19, 1999