OPERA OPTICAL BEACON variation
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 embodied
