[A-DX] VOA Radiogram slow modes to Australia

Sa Jan 30 15:41:26 CET 2016

Am 30.01.2016 um 12:39 schrieb  [dxld]:
> Using Fldigi <http://w1hkj.com> or TIVAR 
> <http://sourceforge.net/projects/fldigi/files/AndFlmsg/TIVAR/>, try 
> decoding this audio of VOA Radiogram <http://voaradiogram.net> Olivia 
> 64-2000 (25 wpm) and MFSK8 (30 wpm) by a receiver in Sydney, 
> Australia, 15000 km from the North Carolina transmitter ...
> https://t.co/2ike5zvB7Z
> Given the reception conditions, voice would probably be 
> unintelligible, and the faster MFSK32 generally failed.
> Kim


"....VOA Radiogram as received in Sydney, NSW, Australia, 30 January 
2015, 0948 UTC, 5865 kHz, via North Carolina transmitter. Modes are 
Olivia 64-2000 and MFSK8, each preceded by a 15-second tuning signal 
transmitted at 1500 Hz but received at 1384 and 1612 Hz (1612 seems to 
decode more successfully). Transmitter was AM, but receiver was set to 
USB. Some unsuccessful MFSK32 is included at the end of the recording....."

Decoding could be better, but in the audio is a big mistake !!

In audio, there are two signal-centers: at 1500 +/- 100 Hz.
That means:  both Olivia, as well as in MFSK there are two center 
frequencies:  about 1390 Hz + 1610 Hz.

This clearly means:
1.  reception was at 5865,100 kHz (100 Hz higher)
2.  decoding was NOT only in USB, but USB + LSB = DSB,  without S-AM
3   because of that: both NF spectra do not add congruently !!

Thereby:    AF demodulation was NOT correct !!!