Return-Path: Received: (qmail 14446 invoked from network); 23 May 2000 13:47:16 -0000 Received: from unknown (HELO post.thorcom.com) (212.172.148.70) by grants.core.plus.net.uk with SMTP; 23 May 2000 13:47:16 -0000 Received: from majordom by post.thorcom.com with local (Exim 3.02 #1) id 12uEvL-0006sO-00 for rsgb_lf_group-outgoing@blacksheep.org; Tue, 23 May 2000 14:40:43 +0100 Received: from cmailg3.svr.pol.co.uk ([195.92.195.173]) by post.thorcom.com with esmtp (Exim 3.02 #1) id 12uEvK-0006sJ-00 for rsgb_lf_group@blacksheep.org; Tue, 23 May 2000 14:40:42 +0100 Received: from modem-107.aeglos.dialup.pol.co.uk ([62.136.97.107] helo=lvm) by cmailg3.svr.pol.co.uk with smtp (Exim 3.13 #0) id 12uEvH-0000sW-00 for rsgb_lf_group@blacksheep.org; Tue, 23 May 2000 14:40:40 +0100 Message-ID: <000201bfc4bc$a7bde900$6b61883e@lvm> From: "LAWRENCE MAYHEAD" To: "rsgb lf group" Subject: LF: Re. Morse tones filters etc. Date: Tue, 23 May 2000 14:41:08 +0100 MIME-Version: 1.0 Content-Type: text/html; charset=windows-1252 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: Content-transfer-encoding: 8bit

Hi All,

I think that what we have here is re-inforcement at certain frequencies due to the proximity of reflecting surfaces at critical distances(similar to "eigentones produced in a room by the walls) The example given by ON6UX where a tube/Jar is used to enhance signals is most probably a " Helmholtz" resonator (I think thats the name) which can be used to produce a resonance with quite a high Q.

The technique is used in Hi Fi systems in bass reflex loudspeakers,and details can be found in Hi Fi books,also in Physics text books in the sound sections.Could be very intresting to try an experiment.734s Laurie.