DX Hellschrieber, from VK2ZAY

March 2, 2009 | Amateur Radio | By: Mark VandeWettering

Alan, VK2ZAY apparently has changed his beacon to send MT Hellschrieber, in addition to his FSK CW.


If you look carefully, you can see VK2ZAY in letters. Very neat!


Comment from Alan Yates
Time 3/2/2009 at 6:32 am

Hello Mark,

Yep, I was doing some other MCU work and realised how easy it should be to implement. When I originally built the TX modulator I had the idea in mind, but I only just got around to trying it.

The “font” is only 5×5 which isn’t the most readable. The code itself supports 8 shift levels (bit-mapped into a byte), a text file defines the pattern. I also need to add predistortion to the modulation steps to compensate for the varactor non-linearity. I added a table to support shift predistortion, but I haven’t yet computed the values needed. I can pick them off my previous characterisation data for the modulator.

So very much WIP, but it is good to see the general idea working.

I’ll post the code once I finish the predistortion.