LF: Re: LF: WANTED 8KHz OP4H OPERA TESTER’S

[Roger Lapthorn <rogerlapthorn@gmail.com>]

Graham,

When I get a new PC (next few months) with a bit more processing power I may give this a try using earth mode at VLF in the Cambridgeshire area. 

My initial Opera tests a few months ago led to all sorts of problems on my 6 year old WinXP PC. Since then I've not reloaded the software. You may remember that the load with Opera was close to 100% and I had a number of other issues that coincided with putting Opera software onto the PC. I hope you can assure me regarding the stability and processor loading with the latest versions. I'm still unhappy that the software is not "open" in the sense that people who know can fully understand what it does. 

73s
Roger G3XBM

On 29 April 2012 20:23, Graham <g8fzk@g8fzk.fsnet.co.uk> wrote:

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 ,

 

 

 

 

 

 

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