sabato 21 dicembre 2013

VOA Radiogram, Dec 21-22, tries a different MFSK64 center frequency

It may be the holiday season, but the experiments continue on VOA Radiogram.

Experiments for the weekend of December 21-22, 2013, involve MFSK64 at our usual center frequency of 1500 Hz, versus a center frequency of 1700 Hz.

At a center frequency of 1500 Hz, the fundamental data is from 1000 to 2000 Hz. The second audio harmonic is from 2000 to 4000 Hz, thus abutting the fundamental. Don't you just hate it when the fundamental is abutted?

Anyway, after transmitting an image at a center frequency of 1500 Hz, we'll transmit it again at a center frequency of 1700 Hz. The fundamental is now from 1200 to 2200 Hz, and the second harmonic is from 2400 to 4400 Hz. We now have a "guard band" between the fundamental and the second harmonic. Will this reduce noise in the MFSK64 images and improve the text performance?

        ! ;   1500 Hz  2nd audio harmonic

             1700 Hz    2nd audio harmonic         
           ----------  ====================

More details about this weekend's program at...

VOA Radiogram transmission schedule
(all days and times UTC):
Sat 1600-1630 17860 kHz
Sun 0230-0300 5745 kHz
Sun 1300-1330 6095 kHz
Sun 1930-2000 15670 kHz
All via the Edward R. Murrow transmitting station in North Carolina.

Sunday, December 22, 2013, will be the last day for the transmission at 1300-1330 UTC on 6095 kHz. Next weekend it will be replaced by Saturday, 0930-1000 UTC, on 5745 kHz. The other times and frequencies will remain the same.

Check out last weekend's picture of the National Christmas Tree, transmitted December 14 at 1626 UTC on 17860 kHz, as received and decoded from Estonia to California.


PS: The Mighty KBC, 7375 kHz via Germany, will transmit a minute of MFSK32 at about 0130 UTC  Sunday (Saturday 8:30 pm EST).
(via dxld yg)