Return-Path: Received: (qmail 3914 invoked from network); 1 Aug 2002 08:54:24 -0000 Received: from warrior.services.quay.plus.net (212.159.14.227) by mailstore with SMTP; 1 Aug 2002 08:54:24 -0000 X-Priority: 3 X-MSMail-Priority: Normal Received: (qmail 28257 invoked from network); 1 Aug 2002 08:54:28 -0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Received: from post.thorcom.com (193.82.116.70) by warrior.services.quay.plus.net with SMTP; 1 Aug 2002 08:54:28 -0000 X-SQ: A Received: from majordom by post.thorcom.com with local (Exim 3.33 #2) id 17aDDj-0004RG-00 for rsgb_lf_group-outgoing@blacksheep.org; Thu, 01 Aug 2002 11:30:15 +0100 Received: from cmailenv2.svr.pol.co.uk ([213.218.77.54]) by post.thorcom.com with esmtp (Exim 3.33 #2) id 17aDDi-0004RA-00 for rsgb_lf_group@blacksheep.org; Thu, 01 Aug 2002 11:30:14 +0100 Received: from [62.21.130.111] (helo=w8k3f0.freeler.nl) by cmailENV2.svr.pol.co.uk with esmtp (Exim 3.35 #1) id 17aBTi-00035G-00 for rsgb_lf_group@blacksheep.org; Thu, 01 Aug 2002 08:38:39 +0000 Message-ID: <5.1.0.14.0.20020801100707.00a17630@POP3.freeler.nl> X-Sender: FRE0000086604@POP3.freeler.nl X-Mailer: QUALCOMM Windows Eudora Version 5.1 Date: Thu, 01 Aug 2002 10:31:37 +0200 To: "LF-Group" From: "Dick Rollema" Subject: LF: "Downward modulation" MIME-Version: 1.0 Content-Type: text/html; charset=windows-1252 Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group Sender: Content-transfer-encoding: 8bit To All from PA0SE

Apparently  my remark that the carrier of Droitwich goes downwards during modulation  has caused confusion. I certainly did not mean "downward modulation" as we remember it from our AM transmitter days, an effect caused by insufficient drive, weak power supply or other shortcomings of the transmitter (or the operator...)

The carrier of Droitwich and BBC World Service is normal as long as there is a modulating signal. But during moments of no modulation the carrier rises to a higher level. As soon as modulation reappears the carrier returns to its normal level.  This can be clearly seen in the attachment to the reflector posting of 31/7 by Jim, M0BMU.
I am sure this is done on purpose and not a matter of poor design, bad maintenance or incompetence of the BBC engineers. 
Dave, G3YXM, in his posting of 30/7 has told us that it is a feature of modern transmitters that can be used to  preserve a silent background in the face of interference.
I can understand that in connection with the BBC World Service but why it is applied to the 198kHz transmissions escapes me.

73, Dick, PA0SE