VOA Radiogram is now Shortwave Radiogram. Please visit swradiogram.net
VOA Radiogram is a Voice of America program experimenting with digital text and images via shortwave broadcasting. It is produced and presented by Dr. Kim Andrew Elliott.
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Results of experiments on VOA Radiogram, 30 Nov/Dec 1 2013
Thanks to all of you who participated in the experiments on VOA Radiogram during the weekend of 30 November/December 1 2013.Here is what we found out:1) Whatever caused the slant in the MFSK images on VOA Radiogram 34, 23-24 November, was resolved this past weekend on program 35. Most of you received unslanted images, even with the Fldigi RX ppm correction set to zero. Of course, the quality of the images varied according to reception.Tarmo in Estonia received and decoded this vertical blue line on 17860:
2) Our experiment with audio harmonics found virtually no difference between the 1500 Hz and 1000 Hz center frequencies for both MFSK64 and MFSK64L. With a center frequency of 1000 Hz, the second harmonic (1000 to 3000 Hz) overlaps the fundamental (500 to 1500 Hz), but this overlap appears not to have had any negative effect on decoding.
The only exception is the image of VOA correspondent Steve Herman, W7VOA, which was transmitted in MFSK64 centered on 1000 Hz…
For many listeners, this picture had an unusual amount of horizontal interference lines. Were these caused by the second harmonic? This weekend (7-8 Dec 2013) on VOA Radiogram, we’ll compare MFSK64 images at center frequencies of 1500 and 1000 Hz.3) The VOA Radiogram broadcast Sunday at 1930-2000 on 15670 kHz was difficult to receive in Europe. This will be typical reception in Europe now that we are nearing the winter solstice. Nevertheless, this transmission is a useful test for the digital text modes. Most of you had success with MFSK16 and most of you were able to decode MFSK32 with few or no errors. The faster modes were more problematic, and the images tended to be fuzzy.Even as 15670 kHz provided poor reception in Europe, it was providing good reception and excellent decodes in western North America, all the way to the Pacific coast.