Click here to see the original article from HR dec.-79.
Dear HR:
The December issue of ham radio describes the Hellschreiber typing keyboard machine, and the article mentioned that the shortest pulses are 8.16 ms, producing a speed of 122.5 baud and a minimum bandwidth of 61 Hz.
Unfortunately for the system, the abrupt rise and fall times involved are quite broad. A similar system that has been on 14140 kHz from the Hsinhua News Agency in Peking for years (but now possibly removed at the request of the Intruder Watch), is more like 3 or 4 kHz wide at a distance 6241 miles; it was hard to live with. There continue to be other signals here in the mornings on 3577, 3595, and 3845 kHz just before the 80-meter band closes to China.
The system I heard during WW2 was used by German fighter aircraft in interception, and directed from ground by this equipment. That was not so bad because vhf was used, and at some distance in frequency from other communications circuits. I think that it is a mistake to encourage the use of this system of 14 emission, which is not authorized by FCC Regulations, Section 97.61, except on frequencies of 51.1 MHz and higher.
My tape of the Hsinhua transmissions was printed by GSXB, who thought it was difficult for Chinese to read, and shows what would be expected when there may be as many as thirty or so strokes in one character. Obvioulsy, that requires rather good facsimile definition or it might not be possible to read.