[A-DX] VOA Radiogram, 25-26 February: Three flavors of MFSK

[Roger]

Am 25.02.2017 um 15:06 schrieb Mike Terry  [dxld]:
> 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.
> With reception conditions apparently improving, we will take a chance 
> with MFSK64 (240 wpm) for one of our news stories this weekend.
>
When using the faster MFSK64-mode  one should also use the possibilities 
of FLMSG. This allows you to check the CRC of the received (formatted) 
texts.



> But if reception conditions are poor, we will also transmit one story 
> in MFSK16 (58 wpm).  Tuning for MFSK16 needs to be precise, so if the 
> RSID does not work, I precede it with a 10-second tuning signal.

A precise frequency tuning is only important for LSB or USB,  if you use 
"own" demodulation carriers
If one demodulates in AM, or in S-AM, the relative distance of the 
useful signal / carrier does not change. So you can always work with a 
FLDIGI fixed to 1500 Hz.

Even a frequency drift of receiver or transmitter of 1 kHz would be no 
problem  -  in AM.


>
> So this will be a weekend to compare MFSK16, 32, and 64, including one 
> image transmitted in both MFSK64 and 32, and another image transmitted 
> in both MFSK16 and 32


Images in MFSK-16 have the lowest resolution, despite the same 
transmission time.
In addition, they are particularly susceptible to interference patterns 
from the audio intermodulation products of the aged station in Greenville.

Perhaps the HAARP transmitters could also broadcast the VOA-radiogram, 
while they heat up the Ionosphere .... ;-)


<http://www.rhci-online.net/radiogram/VoA_Radiogram_2017-02-25.htm#HAARP>

http://www.rhci-online.net/radiogram/VoA_Radiogram_2017-02-25.htm#HAARP


roger