Получил из рассылки, посвященной режиму любительской радиосвязи FeldHell (или Hellsreiber) следующее сообщение, касающееся нашей тематики:
Hi,
Just to whet your appetite...
You might remember that the first use of Hell by radio was on LF, and it pre-dated RTTY by many years! Since MSK is so effective on LF we thought we'd revive Hell, combine it with MSK and give the world a new narrow-band, sensitive chat mode for LF/MF.
Con ZL2AFP is (with my assistance) developing a new Hell program, designed specifically for use on LF and MF. The modulation is MSK, and so the bandwidth is very narrow and sensitivity very good. Speeds 105, 63 and 31 baud are offered. For comparison purposes, the program also offers Feld-Hell mode (on-off keyed) with the same speeds.
On the 105 baud speed this software is completely compatible with IZ8BLY Hellshreiber (in both FM-Hell and Feld-Hell modes) due to the use of a lower resolution font.
The receiver offers an interesting eye diagram for tuning (like CMSK), and TWO different detectors. The traditional ASYNC detector has best sensitivity, but the new SYNC detector alternative (uses a Costas Loop demod similar to CMSK) gives nice clear text with no wandering, provided there's not much multipath.
The 105 baud MSK-Hell 105 is just under 200Hz wide, so appropriate for use on 600m in ZL where the maximum transmission BW is 200Hz. The expected sensitivity of the MSK-Hell 31 is about -15dB S/N in 2.4kHz BW and the transmission is only 50Hz wide. It's not too difficult to tune, and the waterfall display is clear to see at the weakest levels.
My test signals using MSK-Hell 63 have been copied easily in VK2 (range 2200km) on 600m, so expect some good performance!
The new modes work on HF as well, but there's no reason to use the slower speeds and you will run into Doppler problems there. The new software offers nothing for HF operators that IZ8BLY Hell hasn't got (except the SYNC detector), but for LF/MF it's an important step forward.
The software is for Windows and will be on my web site soon,complete with help file. If you'd like to test a beta version, write to Con ZL2AFP (zl2afp at xtra dot co dot nz).
73,
Murray ZL1BPU/ZL1EE
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