Return to KLUBNL.PL main page

rsgb_lf_group
[Top] [All Lists]

Re: LF: My thoughts on ROS

To: "[email protected]" <[email protected]>
Subject: Re: LF: My thoughts on ROS
From: Roger Lapthorn <[email protected]>
Date: Sat, 3 Sep 2011 06:49:52 +0100
Dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=subject:references:from:content-type:x-mailer:in-reply-to :message-id:date:to:content-transfer-encoding:mime-version; bh=VXkX+xuqbCktW3xe3UCrpq/oLuHFoBP4I2z7dvWFBvI=; b=n5kzewKd3YXcSZ16XYzgXe34riQyE4UbBZ4n3eh/kRrddSBO6ZmNWASf201sFAGxH0 n+3t3BSzA2Q86XXXlgR9xUcDpPZpQRPBjVPUJePdk+T8Imj4stKMNGvx4l30s2UXi3EH 9OtSgupLm4GT0BBL9T6LNXr3sItsXmWPCk5VM=
In-reply-to: <8343E1D319EE4CEFB7C9BD20AAF2BFFA@AGB>
References: <alpine.WNT.2.00.1109021927550.976@opc1> <CAHAQVWO0ux32U1HfVED+RLEwSq0oxGWcz1h-c6j1PFbxV7e5Og@mail.gmail.com> <8343E1D319EE4CEFB7C9BD20AAF2BFFA@AGB>
Reply-to: [email protected]
Sender: [email protected]
Thanks for the very full reply regarding ROS Graham. 

73s Roger

Via my iPod Touch 4g 2.4GHz handheld. 

On 3 Sep 2011, at 00:32, "Graham" <[email protected]> wrote:

Roger, All
 
ROS HF /MF / Multi access ./ How  did  we  get  here ?
 
Well  as  previously, the  mode   was  designed as a   low  signal   data  mode  optimised  for  LF/MF  , the  origins  are  routed  in the  early  days  of the  ROS  project, when  un-wittingly Jose  had  accurately  described  the  function  of the  mode  (then HF only) as , shall  was say 'dispersed spectrum' , which  triggered  an  all  too  well  documented  response 
 
In the  midst of all  this the  EU decided  by the  use  of  'English'  to define the  telegraphy channel  maximum bandwidth  for  500  as  100 Hz , which, by 'syntax error'   resulted in the  authorisation  of  'narrow data  modes'   after a  poll  conducted on   this  reflector  over  bandwidth  allocation's  I suggested to  Jose , that  a  100  (99)  Hz   narrow  mode  would be  usable  on the  as then ,new,  500  allocations.
 
Followed  then was  quite a interesting  development  path , being  actually  able  to  use  the  experimental  licence  to  conduct  'experiments'  , the  mode was  coded  as  MF-1  and  MF-7  , 7 giving a  similar data  rate to  PSK31 with   approx  12/15 dB  lower  s/n  performance. Initial  tests  had shown PSK31  to  be  virtually useless  on 500 , the  MF-1  provided  reliable  decodes  some  -2  to  -3dB  past the  point  wspr  stopped  decoding (tested on a stable 500 Khz  350 mile day  time  path  via  delft) , where was  I think  the initial  QSO  was  with  Jim  using  MF-7  , resulted in the  first  'long'   data  qso  on 500  , which was  also  decoded  in France .
 
Only   lately  was it  pointed out, that  the  MF mode  differed  from the  HF mode, in that , 'dispersal'  techniques  are not  used in the  data  coding  path, the  reason being , s/n gain can  only  be  realised  via   bandwidth  and  100  hz is not sufficient for the  technique to  be applied .. so  If you  observe  a   MF beacon, the  modulation  'pattern' is  repeated.
 
The  HF  mode  differs  in that  frequency 'dispersion'  is  controlled by  randomization   as  part of the  data  path , this affords  improved s/n  performance  over  the  HF > UHF  path with  wider  frequency  tolerances  , conventional  processing  is  also  deployed, as well  as  FEC .. these techniques re  common to  other  data  modes  , but as this point  'we'  enter  the  un-known as  John call's  it !
 
So  in part  answer to  Roger's  question  , over  multi  access ,
 
There  has been  added  a  modification  to the  code   routine , which , by  use of the  call  sign, causes a  unique locking  sequence  to  be  generated,  use of which  may  be  selected  by  the decode  switch .
the result  being  , that  all  stations  may  be  decoded  , but  if the  call  of a  wanted / qso  station  is  entered  , then the  software  will  only  enter the  lock  phase  when that  station  is  detected .
 
Use  is  made of the  overheads  in the  transmission system, affording the  mode  the  ability  to  withstand   'data' collisions , hence  more  than  one  station  may simultaneously  use the  same  frequency.. as once locked, the  digital  recovery process  , rejects  'non locked'  data  as  (HF)  noise. Limitations  exist  as  to  signal  levels  etc  , but  the  skip distance  experienced  on HF has  enabled  the  system to  function  quite  well. both the   2k and  500 Hz  versions  have  the  feature , the  500Hz  version  suffering  more  from  collisions  but  still  is quite  functional
 
Multi  access  is  therefore  not  available   to the MF mode, but  as  the  mode  is  100 hz wide  , its  quite  possible  to  simply  QSY , the  reasons  for the  defined  channels  are  simply  , that  its not  possible to  casually  intercept  a  ros  transmission,  you  have to  be  on  frequency  and  capture the  lock  sequence  for the  frame  to  decode, it  is  in effect  a  packet  data  system , coupled  with the  sub-audio  and  signal  levels  below  the  waterfall  resolution  , invisible  ros  as Mal  coined  it  ,  defined channel  operation    was the only  way to ensure  decodes ,  wider  AFC  was  possible  but  at the  expense  of  cpu loading, unlike   most  modes, the   audio frequency is  'fixed'  mouse  click/tune  is not  possible
 
In passing,
 
The   display  is  slightly unique , the indicated   levels  are  of  engineering  significance , a limited  user  guide  exists,  the  author  is  the  sole  developer, there  is  remote  internet access built in, remote  station  configuration  via  the  internet for  remote beacon  operation , a  'msn'   internet chat  function  is  provided ,  cat  function  for  most radios  , and a  repeater function  on band  or  cross  band . it is  primarily a  data  communication  mode , unlike  wspr  which  was  developed  as a auto  reporting  beacon mode.
 
Personally In have  suggested  that  some  HF frequency's  for the  MF mode  be defined  as   its  performance  in cross  band  qso with  80  has been   exceptional , however  ... one  day may  be  .. but  we all  have  dials  hi
 
I hope  that  fills  in  the  gap's to  date !
 
73  -G..
 
 

Sent: Friday, September 02, 2011 9:37 PM
Subject: Re: LF: My thoughts on ROS

Well, I agree with GM4SLV's comments on ROS, although my experience is very limited and RX only so far. I have successfully decoded G0NDB, G4WGT and GM4SLV on 500kHz.

Like Mal and John, I also found the user friendliness of the software lacking: the array of dials presented is impressive but rather meaningless apart from the one on the left dealing with audio level. The dials may be meaningful to some. I appreciate this is a "one man job" and very credible too, but the UI does seem less user friendly than WSPR for example.

The spots for other bands, are indeed annoying and irrelevant.  I wanted the spots for 500kHz to remain but these disappeared soon after appearing.  When I first fired up the software I had no idea what should happen and there seemed little FAQ data to help understand things.  Did I miss the basic "getting started" user guide? Eventually bleeps happened and signals appeared, but this was more by luck than plan.

Unlike WSPR I am still confused about how several stations can operate at the same in the same sub-band, although this may be my lack of understanding. On 14MHz there seems to be 3 unique channels for ROS, so does this mean on 500kHz there is just one? With WSPR there can be around 200 stations happily co-existing in just 200Hz of band over an hour or so because of time and frequency separation.

In summary, I was pleased to give ROS a successful go the other night (on RX) but I doubt I'll stick with it either.  Like John P-G I'd like to give some other weak signal FSK 2-way communication modes a go on 500 and 136kHz.

73s
Roger G3XBM


On 2 September 2011 20:51, John P-G <[email protected]> wrote:
LF,

One of my objectives listed on my application for a NoV for 500kHz was to
assist other UK stations in their own experiments, acting as remote eyes
and ears, and it was in this role that I accepted Graham's request to join
him and others using ROS.

The mode has had a huge amount of press - negative and positive - and
being a one-person development (and closed source) is certain to be
controversial.

After installing the software on my NetBook (Samsung NC10 - the only
Windows PC I had available) I was initially bewildered by the look, feel
and configuration of the beast.

The continuous appearance of information relating to bands quite unrelated
to the band you've selected is annoying and, on the small screen of a
NetBook, very distracting - taking up valuable window space.

The MF mode, with it's 2 symbol rates, is nicely compact, in 100Hz
bandwidth, and the modem seems very sensitive - often (on a quiet band)
giving 100% copy of signals that were inaudible in the speaker and
invisible on a separate RX/waterfall (the netbook screen is too small to
allow me to use the ROS waterfall).

In the presence of lightning static crashes I found it less sensitive,
often failing to lock on weak signals, but coping only with those that
were both audible and visible.

As a QSO mode - yes it probably does very well, but the user interface is
awful - little documentation to get the casual user started - and the
continuously and pointless spots of other bands is enough to drive one to
distraction - and there is no way of storing a sequence of spots on the
band you're operating on, which means you can't easily digest just who has
reported your last transmission before it disappears, replaced by a spot
on 50MHz...

I am always interested in digimodes for QSOs, not just for beacons, but
ROS falls short, I'm afraid.

Mal's reported problems with both ROS and WSPR decodes failing might be
more a problem with his computer - as most people manage to decode WSPR
signals from the very weakest (just visible) at -30dB up to the very
strongest (bright white trace) at +10dB or more. Failure on stronger
signals is generally a timing issue - soundcard sample rate errors - and
failure to decode in general is a PC clock timing issue - the PC /MUST/ be
synchronised to UTC - via NTP/Dimension 4 or whatever. Window's own
inbuilt "network time sync" just isn't good enough.


Now - anyone want to try some other datamode (FSK only, Class-E amp) tests
this weekend?

For tonight I've got a CW beacon running on 501.5kHz but would be happy to
try a CW QSO if anyone hears me. Can't do x-band - no HF antenna....

Regards,

John
GM4SLV




--
http://g3xbm-qrp.blogspot.com/
http://www.g3xbm.co.uk
http://www.youtube.com/user/g3xbm
https://sites.google.com/site/sub9khz/



<Prev in Thread] Current Thread [Next in Thread>