Friday, May 03, 2013

VOA Radiogram for May 4-5

VOA Radiogram for May 4-5: All MFSK, with another Flamp

In the next few weeks, we will be transmitting more MFSK32 and MFSK64, and comparing these two speeds of MFSK. MFSK64 (240 wpm) would allow us to put more information into a broadcast, but MFSK32 (120 wpm) would perform better in difficult reception conditions.

Last weekend, after using Flamp to transmit a VOA news story twice, some of you successfully received more than 90% but not quite 100% of the blocks. This weekend, we will use Flamp to broadcast a VOA news story three times. Please use Flamp 1.0.x.; the experimental version Flamp 2.0 is not compatible with Flamp as currently transmitted on VOA Radiogram.

The question for us is whether it makes sense to use Flamp (or similar future app) to transmit a news story two or three times using a fast mode like MFSK125, or just send the story once using a slower but more robust mode, like MFSK32 or MFSK64.
Here is the schedule of modes for the May 4-5 VOA Radiogram:

MFSK16: Program preview
MFSK32: Two VOA news stories
MFSK32: Image to accompany story to follow
MFSK32: VOA news story in Flmsg* format
MFSK64: Same VOA news story in Flmsg* format
MFSK128: Same VOA news story in Flamp* X3 format (compressed**)
MFSK16: Closing announcements
MFSK32: Image

An MFSK16 mode ID will precede each mode transmission.

All modes (except for one surprise mode) will be centered on 1500 Hz.

*Download Flmsg, Flamp 1.0.01, and Fldigi from
**Because it is compressed, you will not see recognizable words during this Flamp transmission

Two interesting suggestions sent by listeners:

John Hoskins WA5NJG runs two instances in Fldigi during VOA Radiogram. One is set permanently to MFSK16 (no RSID) to receive the mode IDs. The other instance follows the modes being tested.

Ralph Wallio W0RPK suggests turning off Fldigi’s AFC during VOA Radiogram. This will help keep the audio frequency on 1500 Hz, rather than chasing a noise up or down in audio frequency as sometimes happens with the AFC on.

Please send reception reports to Audio samples of digital text that is successfully decoded during difficult reception conditions are especially helpful.

And visit
Twitter: @VOARadiogram   

 VOA Radiogram transmission schedule
(all days and times UTC)

Sat 1600-1630 17860 kHz
Sun 0230-0300 5745 kHz
Sun 1300-1330 6095 kHz
Sun 1930-2000 15670 kHz

All via the Edward R. Murrow transmitting station in North Carolina.
Wishing you good decoding whether reception is good or not,