WANTED =20 8KHz OP4H OPERA TESTER=E2=80=99S=20

Dreaming of sending data=20 ?

After testing , the Dreamer=E2=80=99s Band 8KHz version of =20 the Opera Beacon system is ready for AIR testing (OR) GROUND testing. The Opera beacon tx time has been extended to =20 4 hours to give maximum sensitivity , while maintaining transmit times in keeping with the 8K activity at the moment

At =20 approximately 50 % = duty=20 cycle , the system will transmit 2 =20 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 =20 approx randomly = 50% of=20 the data during the Tx time required to = achieve a decode.

Decode sensitivity is estimated to =20 be = approx -47 dB , but this is based on the sim-path calibration and may extend lower in actual use.

In tests , a=20 signal , modulated = by=20 the Opera on/off keying , level reduced to 'normal off = air'=20 was demonstrated = to leave a trace on =20 =E2=80=98Spec Lab=E2=80=99 so station=E2=80=99s using Opera will also show as =20 per normal on the web based grabbers etc, with the additional possibility of Opera=20 decodes.

As in the =20 LF>HF versions = ,=20 Opera utilises the PC sound card for both Tx =20 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=E2=80=99s over short MK1 back garden test ranges.

Users operating at 8Khz will show on the=20 psk-reporting map = as band=20 =E2=80=98unknown=E2=80=99, both = Tx and Rx =20 stations are = included in the display to ensure maximum visability.

Transmit =20 Keying

Tx =20 keying is provided by way of =20 a direct audio drive from the sound card or =20 by way of on/off keying by the com-port ptt key output from the software. An additional com = port may be=20 addressed to perform station Tx/Rx functions at change over. Due to the=20 longer time scales, the switching times of = heaver=20 'power' relays will not affect system = performance,=20 simplifying switching if need be. =

Rx requirements =

Receive is =20 facilitated by the =20 direct input to = the sound card at the 8Khz operating frequency , no filtering or =20 pre processing = is required, however, the =20 receiver is of fixed bandwidth so if = using=20 external oscillator , its important to ensure = the =20 signal falls within the bass band.

Compatibility = ,

Opera =20 is designed = to operate with all =E2=80=98new=E2=80=99 versions of =20 window=E2=80=99s = and is =20 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 =20 transmitted , so = the system may be classed as a data mode .

If there are any questions = etc =20 ,pls contact myself Graham G0NBD or Gary G4WGT , =