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Duplo Hellschreiber
Duplo Hell
Invented by Nino IZ8BLY
The font and format are identical to Feld-Hell, except that two columns are transmitted at the same time, using two on-off keyed tones. The lower tone is used for the left column, and the upper for the right. Rather than operate at double throughput, the transmission runs at the same throughput as Feld-Hell 25wpm, with the dot elements doubled in length.
This mode is remarkably immune to noise, due to the higher integration time for each dot element. but more sensitive to selective fading. This format is , but only available in the IZ8BLY software.
In my experiences it is not a real sensitive mode but should perform real well on upper HF or VHF,UHF