Return-Path: Received: (qmail 13127 invoked from network); 31 Jan 2001 11:38:26 -0000 Received: from unknown (HELO murphys-inbound.servers.plus.net) (212.159.14.225) by excalibur.plus.net with SMTP; 31 Jan 2001 11:38:26 -0000 Received: (qmail 8674 invoked from network); 31 Jan 2001 11:32:31 -0000 Received: from unknown (HELO post.thorcom.com) (212.172.148.70) by murphys with SMTP; 31 Jan 2001 11:32:31 -0000 Received: from majordom by post.thorcom.com with local (Exim 3.16 #1) id 14NvLT-0003hw-00 for rsgb_lf_group-outgoing@blacksheep.org; Wed, 31 Jan 2001 11:22:39 +0000 Received: from tungsten.btinternet.com ([194.73.73.81]) by post.thorcom.com with esmtp (Exim 3.16 #1) id 14NvLP-0003hp-00 for rsgb_lf_group@blacksheep.org; Wed, 31 Jan 2001 11:22:35 +0000 Received: from [213.1.65.192] (helo=default) by tungsten.btinternet.com with smtp (Exim 3.03 #83) id 14NvLA-0002RF-00 for rsgb_lf_group@blacksheep.org; Wed, 31 Jan 2001 11:22:20 +0000 Message-ID: <001b01c08b77$f8a66f40$c04101d5@default> From: "Alan Melia" To: "LF-Group" Subject: LF: Morning noise levels Date: Wed, 31 Jan 2001 11:15:43 -0000 MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1; format=flowed Content-Transfer-Encoding: 8bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 4.72.3110.5 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group Sender: Hi Mike and the Group, If you care to trawl Rik's web site there are several plots on 137kHz when CFH has gone off that indicate the noise here is related to the oncomming daylight. This is confirmed by observations on Spectrogram that Brian made in Portugal. The noise seems to make a steady decline but the effect is most noticable on a waterfall display about 1 hour before sunrise in the UK. The reponse of a waterfall is different to that of my CFH plots, as the latter are processed to remove sharp spikes of noise, such as static crashes, which may play a big part in the nightime noise pattern. Interesting plots are for following dates:- Oct 26th Nov 15th Dec 14th Dec 15th Dec 18th if you look at the periods when the carrier was cut. I also have a plot where CFH was off for the 16 Dec that I did not lodge with Rik, there is a lot local static (rain?) noise at one stage and much qrm around 137.0 in the morning (G8RW), but that shows a decline of 'non-local' noise of 4-6dB between 2400z and 0600z These graphs may not be as dramatic as is seen on some waterfalls as they are taken with a long time-constant and a form of 'averaging' which only records the lowest of 6 sequential measurements. I still have all the raw data for these dates and could replot all the data 'averaged' instead of 'censored' which might give an indication of the 'subjective' noise levels as well. My explanation of this 6dB decline is the shutting down of the area of received signals (including the storm areas) as daylight approaches. Our biggest area of noises in the UK is to the east. The effect may be different in central Europe, it should be essentially symmetrical. This is based on the opposite effect which occurs in Canada where the S/N is best in the early evening, and degrades about 4 hours after sunset. To this is added the fact that most local noise sources are generally quiet for a hour or so after dawn. Cheers de Alan G3NYK Alan.Melia@btinternet.com