Thursday, February 27, 2014
VOA Radiogram weekend schedule
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 email@example.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 firstname.lastname@example.org . 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 Andrew Elliott
Producer and Presenter