Message-ID: <001b01cce0c1$49ec88d0$0401a8c0@xphd97xgq27nyf>
From: "mal hamilton" <g3kevmal@talktalk.net>
To: <rsgb_lf_group@blacksheep.org>
References: <006201cce044$06c16f80$0401a8c0@xphd97xgq27nyf> <3A9A60CAE4EB4355A5B0A30CDA0F450A@JimPC> <AE79F5BD0B964D4CBF8E04AD01E73808@JimPC> <4F287B3F.1040109@talktalk.net>
Date: Wed, 1 Feb 2012 09:10:05 -0000
MIME-Version: 1.0
Subject: Re: LF: Re: Opera v qrs evaluation
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QRSS does NOT get lost or missed  in the noise as you suggest and one can
always see at least part of the information trace, whereas Opera is all or
nothing and I have noticed at times a TRACE but NO DECODE.
I wonder what your next distortion of the facts will be
g3kev

----- Original Message -----
From: "qrss" <qrss@talktalk.net>
To: <rsgb_lf_group@blacksheep.org>
Sent: Tuesday, January 31, 2012 11:37 PM
Subject: Re: LF: Re: Opera v qrs evaluation


> Dear Jim, Rik, Laurence
>
> Thanks for the information, it does seem from all tests that QRS3 and
> OP4 are about equivalent.
> QRS as we know takes a human to notice its there among noise and can get
> missed. With OPERA (and WSPR) if there is an RX on in range it's de-coded.
>
> 73 Eddie G3ZJO
>
>
> On 31/01/2012 22:51, James Moritz wrote:
> > Dear Eddie, LF Group,
> >
> > I did a rough and ready comparative test on the "sensitivity" of QRSS3
> > and Op4 using your back-to-back transmissions. For 500kHz reception,
> > broadband noise from the broadcast stations just east of here is being
> > nulled out using a loop oriented N-S. Rotating the loop out of the
> > null position gives a convenient way of adjusting the SNR on Eddie's
> > signal. So I increased the noise level until I judged Eddie's QRSS was
> > just fully readable (using 0.3Hz FFT resolution), then left everything
> > in the same position for 4 transmissions, during which signal and
> > noise levels stayed nearly constant (see the attachment). Opera
> > reported an SNR of -31dB on Eddie's Op4 signal for all the
transmissions.
> >
> > So, from what Graham said, Op4 may have a small margin in SNR with
> > these conditions. You could argue about what constitutes "readable"
> > QRSS, but there can't be more than a few dB difference between this
> > signal and something indecipherable without prior knowledge. It takes
> > 4 minutes to send a callsign using Op4; you could increase the dot
> > length perhaps to 4s  and transmit most callsigns in 4 minutes, which
> > would gain you about 1.2dB. But for practical purposes I think, in
> > this test anyway, the two modes are approximately equivalent in their
> > efficiency in sending callsigns.
> >
> > Cheers, Jim Moritz
> > 73 de M0BMU
>
>