Slow Scan Radio has been transmitting two streams of text simultaneously. We
have tried this a few times on VOA/Shortwave Radiogram, and will try it again
this weekend.
Near the end the half hour will be a simultaneous
transmission of a news item from swissinfo.ch in two languages, both in MFSK32,
with the English version centered on 1500 Hz and the Spanish version centered on
2200 Hz.
Why 2200Hz? The "primary" MFSK32 occupies audio spectrum
approximately from 1250 to 1750 Hz. This sometimes results in an audio harmonic
from 2500 to 3500 Hz. MFSK32 at a 2200 Hz center frequency occupies 1950 to 2450
Hz, placing it above the primary MFSK32 but below the harmonic.
One way
to decode both is to run two instances of Fldigi, one with the RxID turned on,
and the other with the RxID turned off. For the second instance, manually adjust
the audio frequency using the ten-second tuning tone.
Another method,
requiring only one instance of Fldigi, is to record the broadcast of Shortwave
Radiogram, and decode the 2200 Hz text from the recording.
This
simultaneous transmission begins at 25:02 into the half-hour
broadcast.
Last week's Thor 50x1 performed well, especially for its
speed, but not as well as MFSK32, and sometimes even not as well as the faster
MFSK64. I was able to test this during the Sunday 0800 UTC broadcast using an
SDR in Japan tuned to 5850 kHz. This is one time of the year that the Sunday
0800 UTC show has a better than usual chance of successful reception and
decode.
Here is the
lineup for Shortwave Radiogram, program 93, 29-31 March 2019, in MFSK
modes as noted:
1:47
MFSK32: Program preview
4:05 SSTV transmissions from the ISS on 1-2
April
5:49 MFSK64: Improved design for lithium-sulfur batteries*
10:15
Images of the week*
24:56 MFSK32: Swiss worry about 5G antenna health
effects**
28:27 Closing announcements
* with
image(s)
** simultaneous English and Spanish, as discussed
above
Please send reception reports to radiogram@verizon.net
And
visit http://swradiogram.net
Twitter:
@SWRadiogram or https://twitter.com/swradiogram (visit during the
weekend to see listeners' results)
Facebook group: https://www.facebook.com/groups/567099476753304
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