FM Hell is a Hellschreiber mode. The Hellschreiber modes FELD HELL, PSK HELL, FM HELL and HELL 80 are
graphical modes where characters are drawn and the interpretation done by the
user. For FELD HELL, the transmission is done by On-Off keying (OOK) as in CW,
by BPSK for PSK HELL and by AFSK in HELL 80 and FM HELL (MSK in fact).
This mode is included into the software MULTIPSK by Patrick F6CTE, there is the description of this mode and its
variants as well as the specifications coming from his software :
Click on the copy of the screen in order to
listen to the corresponding audio
Createad by : Nino Porcino (IZ8BLY) and Murray Greenman (ZL1BPU)
Baud rate : 105 or 245
Matrix : - for FM HELL 105 bauds…height: 6 pixels and width: 7 pixels
- for FM HELL 245
bauds…height: 7 pixels and width: 14 pixels
Speed : 25 wpm
MSK with a "minimum" shift between tones of 122.5 Hz (at 245 bauds).
The white is at the upper frequency and the black at the lower one.
Receive mode : USB
Character set :
all ASCII printable characters except small letters, carriage return (+
line feed) and error correction character. The used font (FeldHell) is
derived from the font of G3PLX (Peter Martinez),
Shape of pulse : rectangular
Bandwidth : about 130 Hz for 105 bauds and 300 Hz for 245 bauds,
Synchronization : no need, each column is displayed vertically 2 times (but transmitted once)
Pmean/Ppeak : 1
Lowest S/N : - 10 dB for the 245 bauds mode
the Multipsk "105 bauds" is not a "105 bauds" as described previously.
It is, in fact, a mode similar to the 245 bauds and using the same
characters (7 x 14 pixels). The difference lies in the frequency
variation which is not the MSK one (i.e. +/- 61,25 Hz) but it is equal
to 61,25*105/245 Hz. When receiving, it comes to the same (modes are
compatible). In the other hand, this solution has the advantage to be
able to use 7x14 pixels characters and so to keep on with a good
Others pieces of information about Hellschreiber modes can be found on the WEB
site of ZL1BPU (Murray Greenman). Pascal F1ULT make a french
translation of ZL1BPU's site on http://f1ult.free.fr.
frequencies for FM HELL (USB)
Valid also for FELD HELL, PSK HELL and HELL 80.
3580, 7035, 10135, 14063, 21063 and