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Hay .. go to chop the spikes somehow
!
tech update .. the initial
sync frame acquires lock , the noise reduction follows
...and how .....
G ..
Sent: Monday, June 21, 2010 9:59 AM
Subject: RE: LF: Re: 137.500 kHz ROS beacon
A little finger trouble from G
:-
3)
Non linear PA is
required
He means:-
3) No linear PA is
required
-----Original
Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Graham
Sent: 21
June 2010 00:19
To: [email protected]
Subject: Re: LF: Re: 137.500 kHz ROS
beacon
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.
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 ?
Sent:
Sunday, June 20,
2010 6:30
PM
Subject: Re: LF:
Re: 137.500 kHz ROS beacon
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.
----- 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.
Gary - G4WGT.
On 20 June
2010 13:48, mal hamilton <[email protected]> wrote:
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.
----- 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.
***********************************************
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
http://www.youtube.com/user/g3xbm
G3XBM
GQRP 1678 ISWL
G11088
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