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 ,
