''Apparently Opera is functioning as a beaconing system, and nothing else.
You basically transmit one information ("I'm there"), and you get a reply by the
internet ("I see you"). Am I missing something here?
Sooner or later, someone here will surely ask that question: On the other
hand, if you are aiming for two way communication, and there is no SNR
advantage, then why would you want to replace the Morse key in the first
place''
There was (is) a working QSO
version with 15 chrs at -20 dB
s/n and a lower s/n one briefly
that was used on 136 ... however as in
all theatrical productions , artistic
control is under the director and we have one of
the more radical ones on this project
..never a dull moment , but technically so far we
are playing to a full house :- )
Well at least Blagging and
Bragging is keeping the list running
during the 32 min tx cycles ...
but on the bright side OP's
and OAP's are asking questions , which
compared to the other news groups , seems to
reflect a higher level of technical interest down here ,
Joes reply to Stefan was correct .. but .. with
more tones ..fsk can be better and have no
transmission overhead's
pbsk batter than 4fsk
8fsk the same as pbsk
16fsk then better than pbsk
G..
Sent: Wednesday, September 12, 2012 5:39 PM
Subject: Re: LF: RE: [rsgb_lf_group] Re: LF: slow
WSPR?
Hi Graham,
LF,
wow such a flood of incoming mails...
> Well yes Joe (K) is right, BPSK is better, but needs a linear system
to transmit .... Joe (EA) has stated, he could extract another 6 dB if the
modulation system was changed ......
BPSK vs. ASK? Unfiltered PSK _can_ be sent by a nonlinear transmitter, it's
only very unfriendly to others due to the spectral sidebands from the sharp
transitions. But so is unshaped ASK!
In simple words, ASK steps from 1 to 0 wheras BPSK transitions go from +1
to -1. So with BPSK you get twice the sensitivity, along with twice the
keyclicks. If you compare ASK at a given peak power to BPSK sent at -6 dB, you
end up at same sensitivity and same clicks. Only average power for PSK would be
half (25% instead of 50%).
Phase-continuous FSK as used in WSPR is much more gentle in that respect.
There are no steps in the waveform, thus the click spectrum falls off much more
rapidly.
> WLOF is already coded and makes use of multi pass to gain s/n, but is
psk and needs a liner system ...and is not a one-pass decode system , when the
s/n is low .but at -41 dB, by what ever scale, OP32 is well into the noise in
single pass
The advantage of such a "multipass" system is that it can be adaptive to
SNR, ie. a strong signal decodes fast, and only for a weak one you have to wait
longer.
> We didn't set out to produce a low level beacon mode, it was supposed
to be a replacement for the CW key ..
Apparently Opera is functioning as a beaconing system, and nothing else.
You basically transmit one information ("I'm there"), and you get a reply by the
internet ("I see you"). Am I missing something here?
Sooner or later, someone here will surely ask that question: On the other
hand, if you are aiming for two way communication, and there is no SNR
advantage, then why would you want to replace the Morse key in the first place?
> The Op structure allows for up to 50% loss of signal randomly along
the time line, ie first 50%, last 50% or randomly distributed
Yes with Opera's distributed and redundant coding you can chop off half of
the signal time. WSPR can do the very same stunt. Both will need more SNR during
the remaining half, at least 3 dB, probably a bit more. Even DFCW could do it if
you had sent two repetitions at double speed ;-)
> and over a real path , the Op system is able to make use of deep
variations in fading and is immure to phase and Doppler distortion.
Yes of course, on the air there are other factors than "AWGN" white noise.
Spherics and impulsive QRM have to be dealt by appropriate (preferably
wide-band) noise blanking strategies. Fading and Doppler (which is only milliHz
on LF) may have to be dealt with. But it remains to be proven that under these
conditions Op is so much superior that it can make up for the 6 dB shortfall
under lab conditions.
> But, 'the eating of the pudding is in the proof of the making'?
Stefan, last night reaching ua0aet over land, with 7 dB left in the system,
taking some big bites out of the distance records on 136
Yes, a very nice result! I can state without envy that Stefan has a good
signal, and it is going further than others. But does that really make a point
for Opera, versus any other mode?
Graham, I'm in no way against Opera mode per se. But I have to say that I
dislike the bragging.
> The best thing about the Op system is 'The number of reason's it
cannot work' :)
Hey, that's what all those perpetuum mobile inventors keep claiming
;-)
Best 73,
Markus (DF6NM)
Re: LF: RE: [rsgb_lf_group] Re: LF: slow WSPR? Von:
Graham < [email protected]> Datum:
Mi, 12 Sept 2012 12:24 pm
Re: LF: Fwd: Re: Ideas for a slower WSPR for the 137 khz band
Sent:
Wednesday, September 12, 2012 1:08 PM
Re: LF: RE: [rsgb_lf_group] Re: LF: slow WSPR?
Datum: Mi, 12 Sept 2012
4:16 pm
Re: LF: Fw: LOST TRACK
Datum: Mi, 12 Sept 2012 5:18 pm
...
-----Ursprüngliche Mitteilung-----
Von: Graham
<[email protected]>
An: rsgb_lf_group
<[email protected]>
Verschickt: Mi, 12 Sept 2012 4:16
pm
Betreff: Re: LF: RE: [rsgb_lf_group] Re: LF: slow WSPR?
Well its mostly a silly argument as the systems are totally different
, in terms of data processing and the operation of the decoder and the
technical level of the equipment needed to tx/rx the mode
We didn't set out to produce a low level beacon mode , it was supposed
to be a replacement for the CW key .. the longer times where as a
result of studying the various EU/VK qrsss plots and reasoning that
over 50% of the 32 min cycle could be above the decode level ... the
rest (will be) history :)
DSP and associated 'Numeric Processing' facts and fictions are very
difficult to separate , not helped by the ongoing pie fight out to
'our' west , however... so far so good !
The best thing about the Op system is 'The number of reason's it
cannot work' :)
G..
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