WANTED
8KHz OP4H OPERA TESTER’S
Dreaming of sending data
?
After testing , the Dreamer’s Band 8KHz version of
the Opera Beacon system is ready for AIR testing (OR) GROUND testing. The Opera beacon tx time has been extended to
4 hours to give maximum sensitivity , while maintaining transmit times in keeping with the 8K activity at the moment
At
approximately 50 % duty
cycle , the system will transmit 2
hours of carrier in every 4, so should reduce the electricity bill !, while sending the full call sign , as in the LF>HF versions , the decode criteria remains at
approx randomly 50% of
the data during the Tx time required to achieve a decode.
Decode sensitivity is estimated to
be approx -47 dB , but this is based on the sim-path calibration and may extend lower in actual use.
In tests , a
signal , modulated by
the Opera on/off keying , level reduced to 'normal off air'
was demonstrated to leave a trace on
‘Spec Lab’ so station’s using Opera will also show as
per normal on the web based grabbers etc, with the additional possibility of Opera
decodes.
As in the
LF>HF versions ,
Opera utilises the PC sound card for both Tx
and Rx and requires NO high stability oscillators or time synchronisation , all testing being conducted with normal soundcards, mostly with local Tx and Rx using very small Ae’s over short MK1 back garden test ranges.
Users operating at 8Khz will show on the
psk-reporting map as band
‘unknown’, both Tx and Rx
stations are included in the display to ensure maximum visability.
Transmit
Keying
Tx
keying is provided by way of
a direct audio drive from the sound card or
by way of on/off keying by the com-port ptt key output from the software. An additional com port may be
addressed to perform station Tx/Rx functions at change over. Due to the
longer time scales, the switching times of heaver
'power' relays will not affect system performance,
simplifying switching if need be.
Rx requirements
Receive is
facilitated by the
direct input to the sound card at the 8Khz operating frequency , no filtering or
pre processing is required, however, the
receiver is of fixed bandwidth so if using
external oscillator , its important to ensure the
signal falls within the bass band.
Compatibility ,
Opera
is designed to operate with all ‘new’ versions of
window’s and is
compatible with running multiple sessions of Spec-Lab and Opera on the same PC
Function
The OP4H system , will provide the same data as the high frequency variants , s/n reporting via the web or local s/n copy if not web linked. The full call sign is
transmitted , so the system may be classed as a data mode .
If there are any questions etc
,pls contact myself Graham G0NBD or Gary G4WGT ,
