Neat multiplexing test on VOA RadioGram

For those that hang out with us on FLDIGI, you'll remember that we did some nets where we had multiple modes running in the same audio bandwidth.  Olivia 8-500 on the bottom, MFSK-16 in the middle, and some PSK-125 at the top.  All you have to do is run multiple instances of FLDIGI to the same soundcard.  You can even transmit two or three modes simultaneously.

Looks like VOA is getting into the game.  See below:

Hello friends,

 

This weekend’s VOA Radiogram will include some experiments.

 

Simultaneous text and image. One experiment will be the simultaneous transmission of text and an image. The text of the VOA News story about men overeating will be transmitted in MFSK32 at the usual center audio frequency of 1500 Hz. The MFSK32 image accompanying this story will be transmitted simultaneously at a center audio frequency of 2200 Hz. You will need two instances of Fldigi; that is, start Fldigi once, then start it again. If you cannot run two instances of Fldigi (some operating systems don’t allow it), you can decode the image at 2200 Hz later from a recording. (You could also run Fldigi and MultiPSK simultaneously.)

 

At 15 seconds after the text begins, a tuning signal will help you find the exact center frequency near 2200 Hz. The image itself will start 20 seconds after the tone begins.

 

 

I had to reduce the audio level of both the text and image by 3 dB so that the combined audio of the text and image would not overload the transmitter and your receiver. This simultaneous transmission will be followed by the image only, at 1500 Hz, and at full audio level. 

 

QR codes. The broadcast will include two QR codes.  They look like this …

 

 

You scan the QR code, usually with your mobile device, to obtain information.

 

The first QR code will follow the VOA News Story about Middle East hackers. It will provide the link to the full text of the story. The second QR code will be at the end of the show, with the VOA Radiogram transmission schedule.

 

I don’t know much about QR codes, so your advice would be appreciated. Are the transmitted QR codes too big? Unnecessarily big? How small can I make them? (The smaller they are, the less time required to transmit them.)

 

Here is the lineup for VOA Radiogram, program 138, 21-22November 2015, all in MFSK32 except where noted:

    

 1:32  Program preview

2:44  Earth-like exoplanet may not be habitable*

7:29  New tool to search for extraterrestrial life*

11:13  Analysts warn of Middle East hackers*

20:43  Men overeat to show off to women (simultaneous image)*

23:45  Closing announcements*

28:41  Olivia 64-2000: Transmission schedule

 

* with image

 

Please send reception reports to radiogram@voanews.com .

 

VOA Radiogram transmission schedule
(all days and times UTC):
Sat 0930-1000 5865 kHz
Sat 1600-1630 17580 kHz
Sun 0230-0300 5745 kHz
Sun 1930-2000 15670 kHz
All via the Edward R. Murrow transmitting station in North Carolina.

 

The Mighty KBC will transmit a minute of MFSK32 Sunday at 0130 UTC (Saturday 8:30 pm EST) on 7395 kHz, via Germany. This is part of the KBC broadcast to North America Saturday 2300  UTC to Sunday 0200 UTC on 7395 kHz. Reception reports for KBC reception and decoding to Eric: themightykbc@gmail.com .

 

Thanks for your reception reports. Today I hope to answer the last of the reports from program 130, then I’ll put together the MFSK image gallery from program 131.

 

I hope you can tune in and write in.  Have fun with the experiments.

 

Kim

 

Kim Andrew Elliott

Producer and Presenter

VOA Radiogram

voaradiogram.net