Message-ID: <4F287B3F.1040109@talktalk.net>
Date: Tue, 31 Jan 2012 23:37:35 +0000
From: qrss <qrss@talktalk.net>
User-Agent: Mozilla/5.0 (Windows NT 5.1; rv:9.0) Gecko/20111222 Thunderbird/9.0.1
MIME-Version: 1.0
To: rsgb_lf_group@blacksheep.org
References: <006201cce044$06c16f80$0401a8c0@xphd97xgq27nyf> <3A9A60CAE4EB4355A5B0A30CDA0F450A@JimPC> <AE79F5BD0B964D4CBF8E04AD01E73808@JimPC>
In-Reply-To: <AE79F5BD0B964D4CBF8E04AD01E73808@JimPC>
Subject: Re: LF: Re: Opera v qrs evaluation
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
Sender: owner-rsgb_lf_group@blacksheep.org
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org
X-AOL-SCOLL-URL_COUNT: 0  
x-aol-sid: 3039ac1dc1494f287b6f43e0
X-AOL-IP: 195.171.43.25
X-AOL-SPF: domain : blacksheep.org SPF : none


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