Return-Path: Received: (qmail 19789 invoked from network); 6 Jan 2001 23:48:35 -0000 Received: from unknown (HELO murphys-inbound.servers.plus.net) (212.159.14.225) by extortion.plus.net with SMTP; 6 Jan 2001 23:48:35 -0000 Received: (qmail 7732 invoked from network); 6 Jan 2001 23:51:12 -0000 Received: from unknown (HELO post.thorcom.com) (212.172.148.70) by murphys with SMTP; 6 Jan 2001 23:51:12 -0000 Received: from majordom by post.thorcom.com with local (Exim 3.16 #1) id 14F32D-0005Ei-00 for rsgb_lf_group-outgoing@blacksheep.org; Sat, 06 Jan 2001 23:46:05 +0000 Received: from gadolinium.btinternet.com ([194.73.73.111]) by post.thorcom.com with esmtp (Exim 3.16 #1) id 14F32C-0005Ed-00 for rsgb_lf_group@blacksheep.org; Sat, 06 Jan 2001 23:46:04 +0000 Received: from [62.7.73.142] (helo=default) by gadolinium.btinternet.com with smtp (Exim 3.03 #83) id 14F323-0005Ox-00 for rsgb_lf_group@blacksheep.org; Sat, 06 Jan 2001 23:45:55 +0000 Message-ID: <000f01c0783a$c6049800$11e27ad5@default> From: "Alan Melia" To: rsgb_lf_group@blacksheep.org Subject: LF: PLL inaccuracy Date: Sat, 6 Jan 2001 23:44:28 -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 Andre' that is not my appreciation of how off air standards work. You do not try to get a lock up in 64 microseconds (one frame). In this case the PLL is not trying to compensate for poor short term stability. The short-term stability of the VCO must be excellent. My Droitwich standard can take up to 20 minutes to reach lock after switch-on. The VCO is a very stable VXO which still have reasonable performance when the locking signal disappears. I think you must consider trading time for accuracy. A good PLL should always have the best VCO you can get to reduce the incidental FM. So over 10 minutes of nudging it in the right direction (not compensating for its short term stability) it is easy to see you can get 1000 times (at least) better performance. As you say there will always be a slight error, but it can be made vanishingly small. Cheers de Alan G3NYK Alan.Melia@btinternet.com Alan.Melia@btinternet.com