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Re: LF: Re: 137.500 kHz ROS beacon

To: [email protected]
Subject: Re: LF: Re: 137.500 kHz ROS beacon
From: Roger Lapthorn <[email protected]>
Date: Mon, 21 Jun 2010 08:39:11 +0100
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Graham,

Thank you for taking the time and trouble to give me (and others here) a very full and helpful response to my questions about ROS.

73s
Roger G3XBM

On 21 June 2010 00:18, Graham <[email protected]> wrote:
Ok Roger
 
Well  as you  will  of  noted Mr Ros had a  bit  of a  bumpy ride with  our  friends over  the  pond , so  having a  data  system  coded  for  MF was , perhaps a  bit  of a  unexpected out come  from my  initial  request , however ... we have  one .....
 
2) Spread  spectrum .. well  that is where  it all  started to  fall apart ......  yes the  term is  reasonably  close , but  not  close enough to  fully  qualify , for  example F5WK is  working on a  pic based translator  to  enable  a  dds  to be  driven  directly  from the  ros  software ..  the  tx tones are  defined by  a  look up  table .. not  exactly spread spectrum in the  military  sense ..yes there  is a  mixing  of  digital  noise with the  tx data  stream , but  as everyone  is using the  same  prog free , then  its not  particularly secret ...unlike  say  jolly  windows , that  every one uses  without  access  to the  source code ....mfsk with  fec  may of been a  more  fitting  description .. but the  post  is history  as was/is  the  ensuing flap  ..
 
The  mode  deploys full  power to each tone  burst , ie  a mfsk, phase continues   modulation scheme , the  average  power is  less  than 100% peak  as the  system seems to  tx short ms pulses ..may be  slightly  wrong  on that  , but  gaps do  appear causing my  carrier  led to  flicker  on tx
 
2)  bandwidth  is as advertised , the  ros -mf 1 & 7  is  approx  98 Hz  wide  , coded to  fit  inside the  (new ?) 100 Hz  data  allocation on 500 .. by inspection the  modulation seems to be  very  clean with  no  over  shoot  , unlike mfsk  that seems to  spread  quite  badly ,  I note that  137K  band plans  talk of 200  hz data bw
 
3)  Non linear  PA  is  required , the  smart x2  harmonic  amplifier Gary and my self deployed gives a  work-round to the  logic  drive  problem , Gary is  transverting to  137 khz  from HF with a  linear  transverter ... however the  class d/e  amp  would  half  the  frequency  and  modulation , so  picking the  x2  harmonic  produced  a  drive  carrier of  274 khz , which then  reduced to  137  at the  Ae  ......
 
4) Well  its a  free system ...... its  running  better  as time  go's on and evolving , some  beacon modes are now  available , cut and  paste , and the  e-mail qsl seems to  work  nicely
 
5)  I  would  say it  already is , running  1 watt  to  my  Ae I can  obtain 100%  decodes  from the  delft  web-sdr  on 500 Khz in mf-1 mode , 2 to 3  watts  for  mf-7 , that's  350  miles , on  7  meg  in qso with  co2dc I have  taken 100% print  with  him running  250 mW to the  Ae   with  50 mW  drive to  my  Ae on 500 , print  was 100% in Harrogate, in tests  last  month , Grays test on 137  as reported by F5WK , was under the visible  level  on the  spectrum  plot  , but  was decoding.
 
1) facts and  figures ..well  I don't  really know  .Mr Ros  has the  info  .. but its not  for  publication .... this is perhaps a sticky point .. but  while it  lasts  its showing what  can be  achieved  . wspr  is a  time  locked   array  processed  system , using  best fit  matching  , ros  is a  free  running  live  data  system, that  is using  digital  noise  reduction / cancellation to  recover the  data and as  such  are  not  really  compatible , it  looks to be  on the lines of the  noise reduction  used in the  military satellite  systems  of the  1980/1990 .. but  in a much  reduced  bandwidth, making use  of  modern  pc  power ... reception of the  initial  sync  frame is  essential  ..  this  process  is  much  more robust than the  main data  flow , but  dose  present a  problem  with  long  qsb   , unlike wspr that  is partitioned
 
From my own experience  as was Michel , I have  seen  the  low  baud  rate  ros  system  produce  100% print  , when  the signal  could not  be  viewed on spec lab or  detected by  headphones   .. so  I think 'we'  are  working  below the  noise , co2dc has  intimated that  the  system  provides a  increase of  20 dB over the  psk31 system over the  path  co/vk , high  immunity  to  phase  distortion is also  provided  by the  modulation  system.
 
Ok Roger , I hope that  fills in the  gaps ...  at the  moment you  still  need the  traditional  audio  to rf  translation  , however f5wk is  working  on a pic  system and the  x2  harmonic  amp  provides a  work  round  for  classe/d  amps  .. but  you  do  need  to  generate  on the intended  Ae frequency to  use the  amp.
 
73 - G ..
 
Nb .. There may be  some  mileage   in using a  logic  gate  digital  mixer to  get on to  frequency ........ would need  a  x2  doubler (logic)   to  get over the  logic  drive  .. but if it works .. opens up  500/137 to  a lot  more data  com's , bit of a  odd  concept . but if it  works .. ?
 
 
 

Sent: Sunday, June 20, 2010 9:41 PM
Subject: Re: LF: Re: 137.500 kHz ROS beacon

Graham,

I'm behind on ROS progress so have a few questions please, if you've time:
  1. How does ROS compare on a weak signal "effectiveness" factor with modes like QRSS3, 10 etc and with WSPR? Is there a "dB better than" estimate for ROS in its various forms?
  2. What sort of bandwidths does ROS occupy on these LF tests? I appreciate it is spread spectrum, so there's not much power at any time on any frequency.
  3. What sort of TX PA is needed - linear or non-linear?
  4. Is the software less clunky than when I looked a few months back?
  5. Is it going to be a serious contender for real QRP buffs like me?
73s
Roger G3XBM

On 20 June 2010 20:46, Graham <[email protected]> wrote:
''''for instance the French stn F5WK cannot hear you'''''
 
Well  , yes , that's the  point  of it  all  , no  noise, no  trace just  100% pure  digital  data rolling over the  land , like the  un-seen  fog  of  progress 
 
IARU - R-1 plan .. 137.4 to 137.6  digital modes , with the note that  CW is 'not allowed' 
 
I think the  test and  the  frequency  went fully  to  'to plan' and paves the way  for a magnitudinal  increase in  data  use on 137 , to date limited by bandwidth  to  psk31 , ros-mf  by  design  occupying on 50%  of the  allowable  space on  137  and 99% of the  100Hz  allocations  for  500K. and  passing via  a  non linear  system , how  long will  it before the  first  live  data  qso  over the  pond ?
 
G .
 
 

Sent: Sunday, June 20, 2010 6:30 PM
Subject: Re: LF: Re: 137.500 kHz ROS beacon

Gary
There are too many variables with these experiments for instance the French stn F5WK cannot hear you but you are S5 solid on 137.5 here at my qth
The RX stations antennas need to be analyised otherwise it misrepresents what you are doing.
Can u pse use frequencies below 136.5 kcs otherwise there is a problem with EU and Russian stations using the area 137 - 137.778 kcs for QRS acty.
also this is the DX window area for the USA and others.
73 de mal/g3kev
 
 
 
----- Original Message -----
Sent: Sunday, June 20, 2010 4:31 PM
Subject: Re: LF: Re: 137.500 kHz ROS beacon

Hi Mal,

Thank you for your report & comments. The mail you replied to gives all the details of equipment in use for the test beacon.

I would like to be able to have a QSO using morse but I have to admit to a complete loss of confidence as I have not used the mode for 25 years which was one year after I passed the test in 1984. Looking back, letting it go was a silly thing to do.

I do enjoy testing out these "weak signal" modes & in the report I received from Michel F5WK last night he wrote that he could not hear the signal or even see it on SpecLab but he got a complete decode. So as a weak signal communication mode it works.

Just to elaborate on the antenna, it is a 12 metre base loaded vertical with a small elevated inductor of 500uH at about 9 metres & a 1 x 3 metre capacity top with a 120uH spiral inductor. In my small garden I have no space to go outwards only upwards.

73,

Gary - G4WGT.

On 20 June 2010 13:48, mal hamilton <[email protected]> wrote:
Gary
If that was you last nite on  137.5 kcs you were strong enough for cw or qrs3 no need to struggle with decodes from elswhere.
also I had a qso with G3XIZ this morning on 137.0 kcs and got 599, he was 569.
Not sure what antenna u were using but it was putting out a fair signal to this qth. Your radiators are probably acting as an antenna above earth.
 
de mal/g3kev
 
----- Original Message -----
Sent: Sunday, June 20, 2010 12:07 PM
Subject: LF: 137.500 kHz ROS beacon

    Hi LF,
Having successfully bench & on-air tested a x2 harmonic amplifier method of driving my G0MRF Class D LF transmitter, I ran a beacon last night (Saturday 19th) on 137.500 kHz.

An extract from my previous e-mail description is shown at the end.

Using the equipment & method described below, the ERP from my 12 metre vertical antenna was around 150mW. The mode was ROS MF-1, 100 Hz bandwidth.

I received the following report from Michel, F5WK in JN18HP, a distance of 410 miles (661 kilometres) in daylight.

>> Not even a faint trace on a QRSS3 spectrum but:

>> RX1: 19:23 @ 5.9 Hz: 9 <STOP> -37 dB
>> RX1: 19:28 @ 5.4 Hz: O4WGT <STOP> -34 dB
>> RX1: 19:33 @ 5.4 Hz: G4WGT <STOP> -31 dB

The x2 harmonic low level amplifier is a simple way of driving a Class D type of transmitter which employs a divide by 2 drive chain. My limitation with multi tone drive is that my DDS VFO will only produce 2 frequencies ie. the main frequency & a CW/Rx offset which has previously limited me to 2 tones as with RTTY & DFCW modes.

Please bear in mind that it will not be suitable for modes like PSK were tones are transmitted simultaneously.

At the moment the 2 small PCB's are precariously lying on the desk, when I have cased them I will publish the circuit & pictures.

73

Gary - G4WGT.
    ***********************************************
    After a few days experimenting & bench testing a method of driving my
    G0MRF Class D Tx on the 137.000 kHz band from my linear transverter I finally
    constructed a harmonic amplifier producing a 274.000 kHz signal from 137.000
    kHz input. An "on-air" trial was conducted resulting in a QSO with
    Graham G0NBD on 137.000 kHz using ROS data mode software.
     
    My thanks to Graham for his ideas & tests.
     
    The mode used was ROS MF-7. The equipment used for the QSO was as
    follows. Kenwood TS-440 to my LF-MF linear transverter producing the
    137.000 kHz signal, followed by a tuned harmonic circuit & buffer
    amplifier whose output was 274.000 kHz therefore at x2 drive for the Class
    D Tx. The x2 signal is then divided by the Tx driver chain in the
    normal way to provide 137.000 kHz to the PA.
     
    This method should also work well using WSPR & other similar modes.
    *********************************************






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G3XBM    GQRP 1678      ISWL G11088
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