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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:
- 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?
- 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.
- What sort of TX PA is needed - linear or non-linear?
- Is the software less clunky than when I looked a few months back?
- 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
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.
*********************************************
--
http://g3xbm-qrp.blogspot.com/
http://www.g3xbm.co.uk
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G3XBM
GQRP 1678 ISWL G11088
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