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From: "Graham" <g8fzk@g8fzk.fsnet.co.uk>
To: <rsgb_lf_group@blacksheep.org>
References: <618970.37366.qm@web28105.mail.ukl.yahoo.com>, <005801cae88f$64116770$0401a8c0@xphd97xgq27nyf> <4BDB2274.14798.2CE59E3@dave.davesergeant.com> <6BE921B6077A41AE814432EC5C9590B1@JimPC>
In-Reply-To: <6BE921B6077A41AE814432EC5C9590B1@JimPC>
Date: Fri, 30 Apr 2010 21:55:03 +0100
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Subject: Re: LF: Re: ROS s/ware
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Thank you for  that  Jim,

As you  well  know ,transmitting  data modes on 500  is not a  simple mater 
and takes a  great  deal  of technical input to  ensure  the  system is  on 
frequency , stable , liner and  fit  for  purpose , and  not  causing 
interference to the  other  two  band users. reports of  over modulation and 
distortion detectable  at  range  may  be  appreciated by the  few, but  are 
in fact an allegation  of  criminal activity as defined in the  1949  post 
and  telegraph act , a  fact  that's  perhaps  not  lost on the real pirates 
of this  world  when the  custom and  excise where  given  durastriction 
over the  implementation of the  act , transmitting  out  of band is 
defined as operating  out side the  terms of your  licence and are 
therefore  in breach of the  act .

As for  trailing  data  modes and yes , fully aware  of the SS  nature  of 
the  mode , and  very  well  it  works too ...
 we should be  mindful  of the reason 'we' are on 500  in the  first  place 
and to the quite  level  headed  approach  of  Ofcom ... sure  SS is banned 
in the  usa and now  after the  second  'Concorde' moment  is the  Domino 
data  mode that  also  used SS .... after the  arrl made good  use of it 
for  disaster  communication over such a  long  period ....

Of  interest  tonight  was the  low  power  qso  between Gary  and  myself 
using the  Ros  eme  mode , with a  power  reduction  from my  station  of 
3 watts  feeding the  antenna   via a  20 dB  attenuator,  30 mW to the 
antenna , which  roughly requires  50 Watt  to radiate  100 mW erp .. a 
thither  reduction  of  500:1  ! This  level  produced  100 % copy  over 30 
miles to a  similar  Ae , the  Ros   500/8  mode  failed at a  signal  level 
of  approximately 10 dB  higher ( I will  check with  Jose, to  see  if this 
measurement is as  expected)

73 - G ..

--------------------------------------------------
From: "James Moritz" <james.moritz@btopenworld.com>
Sent: Friday, April 30, 2010 8:41 PM
To: <rsgb_lf_group@blacksheep.org>
Subject: LF: Re: ROS s/ware

> Dear Dave, LF Group,
>
> >Their first suggested working frequency on 20m put it splattering
>> right over the IARU beacons on 14100, which it seems the developers had
>> never heard of.
>
> "Splatter" usually refers to distortion products outside the signal
> bandwidth of a signal, but these don't really occur with ROS and other
> constant-amplitude, FSK,  modes since there is only a single tone being
> transmitted at any one time, and so nothing else to intermodulate with, 
> even
> if the TX is highly non-linear. So this complaint is technically
> nonsensical, although 14.1MHz obviously isn't a good choice of frequency!
> What people seem to get excited about is that the transmission has a
> bandwidth of 500Hz, or 2.2kHz - somewhat wider than some other modes, with
> the objective of trading off increased bandwidth against achieving 
> increased
> robustness. The theory is fine; finding out if this actually works and
> offers any practical advantages is why we should be trying it out of 
> course.
> The 500Hz bandwidth easily fits into the "digital" segment even of 500kHz,
> so no problem there.
>
> BTW, now getting about 95% copy of G4WGT/ 100% of G0NBD having a QSO in 
> ROS
> 500Hz / 16baud mode - the bandwidth and centre frequency is as 
> advertised -
> see attachment. Might try transmitting later, but have some other problems
> to sort out first...
>
> Cheers, Jim Moritz
> 73 de M0BMU
>
>