Why Hellschreiber is cool.

So I just joined the Feld Hell Club, hoping to become a little more active in one of my favourite modes again. And I thought that this would be a nice opportunity to blog about why I like it.

When I started to be interested in amateur radio, years before I acquired my first license, I was fascinated with SSTV and spent quite some hours monitoring 14,230 MHz. It was clear to me that some day, I wanted to do this myself! Although now I could, I never transmitted SSTV so far. I still think it’s a nice mode, but it also has some disadvantages: Not only does it take up as much bandwidth as an SSB phone transmission, it also has a near 100% duty cycle and transmission times can be quite long. And even if you use templates, SSTV just isn’t the right mode for common two-way QSOs, in my opinion.

Now usually I’m active in PSK and occasionally RTTY or other modern digital modes (I’m not really using phone outside of contests, for a number of reasons), but I also like Hellschreiber (Feldhell) a lot. Here’s why:

  • The duty cycle is very low, therefore perfect for portable operations where you want your batteries to last as long as possible (think FT-817 with no external power source).
  • The bandwidth is also reasonably low, so there is almost no limit as to where in the bands you can use it.
  • It is usually text-only (at least I haven’t seen any graphical content implemented, although that’d be easily possible – and cool), but as the text is encoded in a matrix rather than bytes, encoding problems cannot occur. Also, as everybody can set up the font being used by his or her own likings, it feels just a little more personal than one of the usual text modes like PSK. I mean, voices are individual too, right?
  • There is no decoding algorithm between you and the band. With PSK and similar modes, you hear a beeping sound and either get somewhat readable text or not. When using Hellschreiber, you literally see what you hear and the actual decoding process is done in your head.
  • Tuning isn’t very critical. This might be useful when using homebrew transceivers. Also, it enables you to tune with your rig’s VFO instead of within the software, so the audio frequency remains constant all the time and you don’t need to re-adjust levels.
  • At least theoretically, you could use this mode with no computer of any kind at all – just like it was done when it was invented.
  • It’s just cool. Period! 🙂 (and I probably forgot some points as well)

All in all I think it’s just cool that some communication protocol that old can still be of so much use today. Dr. Rudolf Hell was a true visionary, more than he could know back in the day! I’m always happy to meet other Hellschreiber enthusiasts on the band and I hope more hams will learn to appreciate this mode.

Some practical advice in the end: As Hellschreiber uses short pulses, please be extra careful about splattering. If possible, adjust the audio input to your transmitter using a 0dB sine tone of the same audio frequency you are going to use for your actual transmission. Fldigi, which I am using, has a very handy „TUNE“ button which does exactly that. On a common 100W transceiver, I’d always set it to no more than 50W HF output. This leaves a lot of dynamic range before distortion should occur. On QRP rigs like the FT-817 mentioned before, you’ll probably want to use the available power to the fullest, but at least watch the ALC meter (it shouldn’t show anything). In doubt, it is never a bad idea to monitor your own signal or ask a friend to do it. And please remember that there is nothing polite about giving a fake 599 report.