Return-Path: Received: (qmail 249 invoked from network); 19 Jan 2002 13:48:19 -0000 Received: from unknown (HELO warrior.services.quay.plus.net) (212.159.14.227) by excalibur.plus.net with SMTP; 19 Jan 2002 13:48:19 -0000 Received: (qmail 22253 invoked from network); 19 Jan 2002 13:48:20 -0000 Received: from unknown (HELO post.thorcom.com) (212.172.148.70) by warrior.services.quay.plus.net with SMTP; 19 Jan 2002 13:48:20 -0000 Received: from majordom by post.thorcom.com with local (Exim 3.33 #2) id 16Rvlh-0006eR-00 for rsgb_lf_group-outgoing@blacksheep.org; Sat, 19 Jan 2002 13:42:49 +0000 Received: from smtp-1.visp.telinco.net ([212.1.130.1]) by post.thorcom.com with esmtp (Exim 3.33 #2) id 16Rvlg-0006eM-00 for rsgb_lf_group@blacksheep.org; Sat, 19 Jan 2002 13:42:48 +0000 Received: from [212.1.153.49] (helo=g4jnt) by smtp-1.visp.telinco.net with smtp (Exim 3.32 #1) id 16RvdZ-0003By-00 for rsgb_lf_group@blacksheep.org; Sat, 19 Jan 2002 13:34:27 +0000 Message-ID: <001501c1a0ef$0ea35e60$319901d4@g4jnt> From: "Andrew Talbot" To: rsgb_lf_group@blacksheep.org Subject: Re: LF: G0MRF/SM6LKM DDS VFO and Jason Date: Sat, 19 Jan 2002 13:41:34 -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 4.72.3110.1 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: -----Original Message----- From: Johan Bodin To: rsgb_lf_group@blacksheep.org Date: 19 January 2002 00:34 Subject: Re: LF: G0MRF/SM6LKM DDS VFO and Jason >I think it's time for you to replace the batteries in your calculator. >> That's neat! But I make it 0.0083333 Hz resolution, >I make it 0.00083333 Hz = 10.0000 mHz / 12. >Both are submultiples of 1Hz... OOPS - Can't read exponential notation on a calculator properly. The 4.194304MHz GPS - frequency locked loop seems to be going now. Once locked, it 'blips' within 1Hz at fundamental and in the long term stays spot on. Dividing down, at 262144Hz the mean phase stays constant but blipping every second over abot 15 degrees. So if the fundamental is used to drive a DDS at 137kHz looks like better than 10 deg short term stability and GPS standard in the long term. Ideal for 30s BPSK but not much much good for higher frequency work, 1Hz sidebands ought to be noticable as well. Chip count has gone up to five now unfortunately, One for the oscillator , two for the binary counter, an 8 bit latch and PIC. But all cheap, the unit does lock up within a few minutes of turn on and does not need a high stability VCXO. Just to see how it worked, I also knocked up a conventional PLL using divide by 2^22 and 74HC4046 PLL chip. Did manage to get it to lock to GPS 1pps pulses eventually, but only after forcing the two signals into sync manually then precharging the filter capacitor to give nearly the correct frequency. That way it could be persuaded to lock up in 20 minutes. If started from cold and asked to lock itself, I estimate would take something like 5 - 8 hours ! Andy :-) Thanks for the source code. It explains everything. It's late, CU tomorrow. 73 Johan SM6LKM