ARLA/CLUSTER: Opera Optical Beacon variation

[João Gonçalves Costa]

Pre-release information

Based on the lecture given by Stuart Wisher G8CYW at the RSGB convention, outlining the use of a high frequency audio sub-carrier for optical communications, where the light source was modulated with a 17 KHz carrier to enable various modulations to be carrier above the audio 0>3Khz base band, thereby eliminating most of the QRM.

Following this example , a modified version of the Opera beacon is in development, with direct audio input / output based in the 15 to 17 KHz range, with intended OP0.5 and OP2 modes [ 30 second and 120 second tx cycle time] , OP0.5 has been proven in scatter tests on vhf and OP2 has similar sensitivity as the wspr system.

The Opera beacon system is a free running one pass decode data system, with no internet time locking requirement, utilising On/off keying (ook) of a single carrier, transmitting 256 data bits. Transmission either by way of a keyed audio output, as per normal data mode soundcard interface or a simple com-port cw keyer of an existing 'cw' system, Tx/Rx com-port ptt switching is also provided.

Where as the Tx format remains the same for all, the decoder has variations linked to the assigned band, propagation and, the Tx duration is used to set the sensitivity, with versions from 30 seconds to 4 hours, -20 dB s/n to -50 dB s/n.

CAT control and SDR interfaces are provided as part of the windows based software package, as is a 'PIC Code', which may be used to code a stand alone pic controlled beacon, as is a internet chat facility and spot upload to the psk-reporting web site, decodes from other users are also directly routed to all web-linked users, with single band or 'all' band filtering.

The latest version may be downloaded from http://rosmodem.wordpress.com/

Notification will be posted when the 15/17KHz modem is available

73
Graham G0NBD

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