[Lowfer] Alternative ways to generate Hellschreiber

[John Andrews]

Stan,

Here are two ways:

Using a program like Spectrum Laboratory, run the digimode terminal in 
one of the Hell modes. Take the line output(s) from your sound card and 
feed it into an SSB exciter set for the desired output frequency. SSB 
generators using the phasing method can be done fairly easily, see
http://www.w1tag.com/Phasing.htm for an example. Actually, I'm not using 
that circuit, but an older one with SBL-3 doubly-balanced modulators and 
an audio phase shift board from work. In using the SSB method, you will 
need a linear amplifier to run "chirped Hell" as Jay and I were doing 
the other night. Sequential Hell, however, consists of one tone with a 
constant amplitude, and can be run through a non-linear PA.

Another approach for sequential Hell is to use a DDS chip to generate 
the carrier frequency. A computer or microcontroller program can key the 
carrier and move the DDS frequency in accordance with fonts for the 
various characters. I've got a version of this in my exciter, so I can 
send XES at various slow speeds (and HoHoHo at Christmas <g>). The font 
for each letter can be created on graph paper, using the constraints of 
number of frequency steps and number of dots per character. If memory 
serves, my setup has 10 frequency steps and about 15 dots per character. 
Only one frequency can be sent at a time. As noted above, a non-linear 
amplifier can be used after the exciter. The ZL1BPU exciter:
http://www.qsl.net/zl1bpu/MICRO/EXCITER/Index.htm can be used to send 
sequential Hell.

I'm sure there are other approaches, and others may chime in.

John Andrews, W1TAG