Return-Path: Received: (qmail 17542 invoked from network); 25 Aug 2004 10:21:25 -0000 Received: from unknown (HELO ptb-spamcore01.plus.net) (192.168.71.1) by ptb-mailstore01.plus.net with SMTP; 25 Aug 2004 10:21:25 -0000 Received: from mailnull by ptb-spamcore01.plus.net with spamcore-l-b (Exim 4.32; FreeBSD) id 1BzuzU-000JO1-0x for dave@picks.force9.co.uk; Wed, 25 Aug 2004 11:26:52 +0100 Received: from [192.168.67.3] (helo=ptb-mxcore03.plus.net) by ptb-spamcore01.plus.net with esmtp (Exim 4.32; FreeBSD) id 1BzuzT-000JNs-OZ for dave@picks.force9.co.uk; Wed, 25 Aug 2004 11:26:51 +0100 Received: from post.thorcom.com ([193.82.116.20]) by ptb-mxcore03.plus.net with esmtp (Exim) id 1BzuuB-0004hc-8u for dave@picks.force9.co.uk; Wed, 25 Aug 2004 11:21:23 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Bzuth-0003iW-U7 for rs_out_1@blacksheep.org; Wed, 25 Aug 2004 11:20:53 +0100 Received: from [193.82.116.30] (helo=relay.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1Bzuth-0003iN-ED for rsgb_lf_group@blacksheep.org; Wed, 25 Aug 2004 11:20:53 +0100 Received: from rusty.kulnet.kuleuven.ac.be ([134.58.240.42]) by relay.thorcom.net with esmtp (Exim 4.41) id 1Bzutd-0006Fl-S1 for rsgb_lf_group@blacksheep.org; Wed, 25 Aug 2004 11:20:53 +0100 Received: from localhost (localhost [127.0.0.1]) by rusty.kulnet.kuleuven.ac.be (Postfix) with ESMTP id 6F15A1D71B7 for ; Wed, 25 Aug 2004 12:20:44 +0200 (CEST) Received: from lepidus.kulnet.kuleuven.ac.be (lepidus.kulnet.kuleuven.ac.be [134.58.240.72]) by rusty.kulnet.kuleuven.ac.be (Postfix) with ESMTP id B8B321D71C9 for ; Wed, 25 Aug 2004 12:20:43 +0200 (CEST) Received: from dell-rik.fys.kuleuven.ac.be (pc-10-33-165-177.fys.kuleuven.ac.be [10.33.165.177]) by lepidus.kulnet.kuleuven.ac.be (Postfix) with ESMTP id 5952938018C for ; Wed, 25 Aug 2004 12:20:43 +0200 (CEST) Message-Id: <5.1.0.14.0.20040825115950.00b95a68@u0019445.kuleuven.be> X-Sender: u0019445@u0019445.kuleuven.be X-Mailer: QUALCOMM Windows Eudora Version 5.1 Date: Wed, 25 Aug 2004 12:28:57 +0200 To: rsgb_lf_group@blacksheep.org From: Rik Strobbe In-Reply-To: <001c01c48a86$7eaf87a0$0a03210a@Hugh> References: <002501c44c6a$86f27ee0$e901a8c0@bob2l2u6k2n1g3> Mime-Version: 1.0 X-Virus-Scanned: by KULeuven Antivirus Cluster X-SPF-Result: relay.thorcom.net: 134.58.240.42 is neither permitted nor denied by domain of fys.kuleuven.ac.be X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=no,HTML_MESSAGE=0.001 Subject: Re: LF: Key Clicks Content-Type: text/html; charset=windows-1252 X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Status: No, hits=0.0 required=5.0 tests=HTML_MESSAGE autolearn=no version=2.63 X-SA-Exim-Scanned: Yes Sender: owner-rsgb_lf_group@blacksheep.org Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out_1@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false X-Spam-Filtered: by PlusNet SpamCORE (v3.00) Content-transfer-encoding: 8bit Hello Hugh,

Just look at CW signal as an AM signal.
Assume you have very hard edged "on / off" keying and key an long series of dots at a speed of 12 WPM :
12 WPM = 600 dotlengths per minute (according to the "PARIS" system 1 word = 50 dotlengths), so in fact you modulate an AM TX with a 5 Hz rectangular "audi signal".
The spectrum of this signal will be a carrier with a whole bunch of sidebands in 5 Hz intervals from the carrier. The first sidebands (carrier +/- 5Hz) is useful all the other (higher) sidebands are waste (wasted power + useless bandwidth) and and show up as keyclicks.
As the keying gets softer (longer rise- and falltime of the keying) the higher sideband will become weaker (less keyclicks). In order to have no higher sidebands at all you would have to get modulation (= keying) sinusoidal. In that case the modulation signal has no harmonics and thus keying will be clickless.
So far the theory, because the above assumes a long (a la limite endless) series of dots.
Our real-world CW instead is a rather random sequence of dots and dashes. But regardless how you do the keying the worst condition (largest bandwidth) is a series of dots. This means that the "useful bandwidth" of a CW signal is determined by speed and the maximum "audio component" of the keying can be determined as :

Fmax = WPM/2.4 where Fmax = the highest useful "audio frequency" (in Hz) and WPM = keying speed (in words per minute)

So the ultimate way to get a clean CW signal is to filter they keying signal through a good LPF at Fmax.
But in most cases a simple RC filter will give the best "effort vs. result" ratio.

73, Rik ON7YD

At 10:32 25/08/2004 +0100, you wrote:

Good morning all,
I keyed my original LF TX with a relay - crude, but it got me on the air.

I know many designs just filter the keying waveform to "round off the
corners" of the envelope.
But I read that the best envelope shape is a "Gaussian waveform". This
produces the smallest sidebands.
[ http://fermi.la.asu.edu/w9cf/articles/click/click.html and lots of other
stuff ]
RC and LC filter circuits produce exponential waveforms, although the
waveform diagrams that accompany these circuits in the texts often make then
look as though they produce a gaussian waveform.

My question is ...
Is there a circuit that will produce a nice "gaussian wavform" that I could
feed into an AM modulator to produce really clean CW - or is there no such
thing ?

73
Hugh M0WYE