H.F. DIGITAL "BROADCASTING"

A program experimenting with digital text and images via shortwave broadcasting.
‘Radiogram’ an entirely novel form of international high-frequency broadcasting.voaradiogram.net
Radiogram is soundly premised on modern digital techniques and mitigates longstanding impediments to HF transmission.
Users around the world have documented reception of 50 VOA Radiogram programs in more than 1000 YouTube videos.
Radiogram should not be confused with Digital Radio Mondiale (DRM), which employs digital modulation for sound broadcasting.
Radiogram broadcasts web content via robust, interference-resistant, error-detecting/correcting AM tone modulation,
using standardized formats widely practiced in the Amateur Radio Service.

The user’s ordinary shortwave receiver, tuned to a Radiogram transmission, feeds its audio to a user device.
These could include mobile phones, tablets, laptop and desktop computers and the new ARM-based miniature computers and embedded devices.
The user device decodes the tones and displays text and imagery despite propagation impairments and intentional interference,
and without Internet connection.
Placing the radio near the phone or computer is normally sufficient. No hardwire connection is required.
By adding a simple audio cable between receiver and user device, however, reception can be silent and covert.
No specialized hardware is needed, and the software platform for decoding is long in the public domain.
A more advanced, yet still inexpensive setup would use existing “dongle” technology
that places a software-defined radio (SDR) inside a small USB enclosure.

Such units are available today for a few tens of dollars and widely used by experimenters.
The operating system and decoding software could also be incorporated into the device,
which could boot the computer, eliminating the need to install any PC software.
The user need not be present at the time of transmission to receive content.
He essentially receives a web magazine updated at will and always ready for use.
The user can redistribute it by printing, USB storage, SMS, E-mail etc.
Naturally, the audio tone transmission can be recorded for later playback.

Even when buried well under music or noise, the nearly inaudible recorded broadcast can nevertheless deliver 100% copy upon decode.
Radiogram’s transmission methods provide text at 120 WPM (near to the speed of spoken English) along with images.
Additional languages have been proven, including non-Roman alphabets.
Sent over regular broadcast transmitters (no modifications needed), this approach effectively extends the reach of the transmitter.
In other words, the digital text mode will decode in locations where the audible speech over the same transmitter would be too low for aural intelligibility.
The audio recorded or captured could be replayed over another transmitter to even further extend the reach of the broadcast.

(from: http://swling.com/blog/2014/03/dear-bbg-take-note-of-the-radiogram/)

Obtained from websdr.ewi.utwente.nl:8901
University of Twente, Nederlands
multi-user Web software defined radio (SDR)
5745KHz 0230 - 0300UT 25 Oct 2015
Off-air recorded "VOA Radiogram" sound samples:
MFSK32 Olivia 32-2000 Olivia 64-2000
with closing music

Olivia MFSK by Pawel Jalocha SP9VRC
is a digital protocol, which transmits a stream of ASCII (7-bit) characters, which are sent in blocks of 5
Each block takes 2 seconds to transmit, thus the effective data rate is 2.5 character/second or 150 characters/minute.
The most common transmission bandwidth is 1000 Hz and the baud rate is 31.25 MFSK tones/second.



A weak signal can be resolved even when 10 dB below the noise floor
(i.e. when the amplitude of the noise is 3 times that of the signal).
Commonly used by radio amateurs to transmit ASCII characters over noisy channels in the HF (3-30MHz) spectrum
Olivia MFSK can be 16/500 (16 tones over a 500 Hz bandwidth) or Olivia 32/1000 (32 tones over a 1000 Hz bandwidth).
The possible number of tones available are 2, 4, 8, 16, 32, 64, 128, and 256 more tones give more data redundancy slow throughput and vice versa.
Available bandwidths for Olivia are 125 Hz, 256 Hz, 512 Hz, 500 Hz, 1000 Hz, and 2000 Hz.
Common combinations are 4/125, 8/250, 8/500, 16/500, 16/1000, 32/1000.

First decode on 5745KHz Sat 0930z 10 Oct '15 (QTH Perth Australia)


VOA RADIOGRAM MFSK32 YOUTUBE VID'S

https://www.youtube.com/watch?v=gdPp1Rc4X0M
https://www.youtube.com/watch?v=mEXbQ8W-gqc
VOA Radiogram #103 - 22/3/2015 off air
https://www.youtube.com/watch?v=KA2IcVaU64Y


VOA Radiogram is a Voice of America program experimenting with digital text and images via shortwave broadcasting.
It is produced and presented by Dr. Kim Andrew Elliott (KD9XB).

VOA Radiogram transmission schedule
(all days and times UTC):

Day Time and Frequency
Saturday 0930-1000 5745 kHz      
QSY 5910 kHz 31 Oct 15
QSY 5865 kHz 14 Nov 15
to avoid QRM
from Alcaraván Radio
Colombia on 5910 KHz
QSY 5745 kHz 2 April 16
QSY 5865 kHz 6 Nov 16
1600-1630 17870 kHz      
QSY 17580 kHz 31 Oct 15
Sunday 0230-0300 5745 kHz 1930-2000 15670 kHz

All via the Edward R. Murrow transmitting station in North Carolina.


To decode the digital text and images transmitted on VOA Radiogram, download Fldigi, Flmsg and Flamp from w1hkj.com
See also how to decode the modes.

Also: https://en.wikipedia.org/wiki/Olivia_MFSK