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 ,
