Redundant Digital File Transfer (RDFT)

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Redundant Digital File Transfer (RDFT)
Digtrx intro.jpg
Frequencies 9.24 MHz,9.065 MHz
Frequency Range 9.065 MHz - 9.24 MHz
Mode USB
Modulation PSK
Emission Designator
Bandwidth 1.8 kHz
Location Worldwide
Short Description RDFT is an amateur radio digital mode used to transmit files.
I/Q Raw Recording
Audio Sample

RDFT is an amateur radio digital mode used to transmit files invented by Barry Sanderson, KB9VAK. Uses DPSKDifferential Phase-Shift Keying.

RDFT was designed for radio amateurs to send files, primarily pictures, known as Digital SSTV, although it was not very popular. Now it is used almost exclusively by the Cuban Number Station (HM01).

Original applications for coding, modulating, demodulating and decoding, which use DSP techniques to work with PC soundcard, were written by Barry Sanderson, KB9VAK. The only GUI application (which utilizes applications written by KB9VAK) known to copy the files (but not necessarily decrypt them) is DIGTRX made by Roland Zurmely, PY4ZBZ.

This software has been long abandoned for other modes and has been replaced by HamDRM and other similar digital SSTV software.

Cuban Number Station[edit]

The only station known to utilize RDFT is the infamous Cuban Numbers Stations (Enigma designation HM01). HM01 transmits both a synthesized voice signal as well as the RDFT file transfer mode. Files are sent in .TXT format but are encrypted. This station is known to use the broadcast facilities - via a feeder or other unknown means - of Radio Habana.

Decoding Software[edit]

Hobby Level Software

DIGTRX was developed by Roland Zurmely PY4ZBZ, a Brazilian Ham Radio operator. This software was originally intended for use in amateur radio for Digital SSTV, but is also able to send images and other computer files using the computer's sound card.

Audio Samples[edit]

RDFT Samples[edit]

RDFT Intro RDFT EOTEnd of Transmission
Digtrx intro.jpg

Cuban Numbers Station[edit]

HM01 Waterfall2thmb.jpg

Video Examples[edit]


For up to date listings, subscribe to the UDXF on and see the Numbers and Oddities website

Additional Links[edit]

Additional Images[edit]