Thanks, mal for these wise words!
Df5qg (Homebrew & CW)
Christian Groeger
mal hamilton <[email protected]> schrieb:
>Never replace the MORSE KEY, you do at your peril !!
>Other modes come and go but MORSE lives on
>All Radio Operators know this.
>
>G3KEV
>
> ----- Original Message -----
> From: Markus Vester
> To: [email protected]
> Cc: [email protected]
> Sent: Wednesday, September 12, 2012 4:39 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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