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
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 firstname.lastname@example.org
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.