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Hello
friends,
This weekend on VOA Radiogram,
in addition to our usual MFSK32, we will conduct experiments with Olivia at
different speeds.
In general, the Olivia modes
are too slow for broadcasting. However, we should keep in mind that text via
shortwave can be received unattended, for later retrieval, making speed less of
an issue. Furthermore, the Olivia modes might be more capable of overcoming
co-channel interference than our usual MFSK modes.
The speed of the Olivia modes
increases as 1) bandwidth increases and 2) the number of tones decreases.
However, as the number of tones decreases, the robustness of the mode, i.e. the
ability to decode in difficult reception conditions,
decreases.
On our shortwave broadcast
channel, we will use the maximum 2000 Hz bandwidth. We will transmit about three
minutes of content in each of Olivia 64-2000 (29 wpm), 32-2000 (48 wpm), 16-2000
(76 wpm), and 8-2000 (104 wpm). As the number of tones decreases, and the Olivia
modes become faster, how much does performance deteriorate?
There are RSIDs for each of
these Olivia modes. If you change modes manually, you will have to use the
Custom menu for the 32-, 16-, and 8-tone versions. Even if the signal is so bad
that you can barely hear it, change the modes manually at the appointed time,
and you might see the text. Because of latency in the Olivia modes, text will
not begin to display until a few seconds after the tones
begin.
Here is the lineup for VOA
Radiogram, program 48, 1-2 March 2014:
1:34 MFSK32:
Program preview (now)
2:48 MFSK32:
Introduction to Olivia experiment
4:35 Olivia
64-2000: Excerpt of VOA News story
8:29 Olivia
32-2000: Excerpt from same VOA News story
12:02 Olivia
16-2000: Excerpt from same VOA News story
15:17 Olivia
8-2000: Excerpt from same VOA News story
18:23 MFSK32:
Hospital machinist, with image
26:07 MFSK32:
Closing announcements
Please send reception reports
to radiogram@voanews.com
VOA Radiogram transmission
schedule
(all days and times
UTC):
Sat 0930-1000 5745
kHz
Sat 1600-1630 17860
kHz
Sun 0230-0300 5745
kHz
Sun 1930-2000 15670
kHz
All via the Edward R. Murrow
transmitting station in North Carolina.
MFSK image
preambles
Last weekend's VOA Radiogram,
program 47, brought good decoding results in many parts of the world. One
problem noticed by some listeners is that if the preamble to an MFSK image is
not received correctly, none of the picture is visible. At voaradiogram.net, I
will post mp3 audio of both of this weekend's images. You can "borrow" the
preamble from the mp3 recording and "graft" it into a recording of your
reception of VOA Radiogram 48.
The 0930 UTC
broadcast
The new broadcast Saturday at
0930-1000 on 5745 kHz is becoming very difficult to hear in Europe as we
approach spring (although it doesn't feel like spring here in the USA). I was
hoping for reports of this broadcast from the Asia-Pacific region, but so far
have received none. This past weekend, I did receive my first report from New
Zealand, but it was for the transmission Sunday at 1930-2000 UTC on 15670 kHz --
apparently via a very long path from North Carolina.
The 0930 UTC broadcast does
provide very good reception to the North American west coast, so if you live in
western North America, try unattended reception while you sleep.
In the next few weeks, we will
probably change this broadcast to another time and frequency. This might be
Sunday at 1400 UTC on a higher frequency receivable in Europe and perhaps
farther east.
MFSK64 on The Mighty
KBC
The Mighty KBC will transmit
another minute of MFSK64 Saturday at about 1230 UTC on 6095 kHz, and Sunday at
about 0130 UTC (Saturday evening 8:30 pm EST) on 7375 kHz. Reports to Eric at
themightykbc@gmail.com . The Mighty KBC schedule and other information are at kbcradio.eu.
I'll now begin answering your
reports from last weekend. I hope to hear from you this
weekend.
Kim
Kim Andrew
Elliott
Producer and
Presenter
VOA Radiogram
