Return-Path: X-Spam-DCC: paranoid 1102; Body=2 Fuz1=2 Fuz2=2 X-Spam-Checker-Version: SpamAssassin 3.1.3 (2006-06-01) on lipkowski.org X-Spam-Level: X-Spam-Status: No, score=-1.0 required=5.0 tests=BAYES_00,DNS_FROM_AHBL_RHSBL, HTML_10_20,HTML_MESSAGE autolearn=no version=3.1.3 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by paranoid.lipkowski.org (8.13.7/8.13.7) with ESMTP id tAPM4icx023720 for ; Wed, 25 Nov 2015 23:04:44 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1a1i85-0002tZ-UK for rs_out_1@blacksheep.org; Wed, 25 Nov 2015 22:01:33 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1a1i85-0002tQ-Ks for rsgb_lf_group@blacksheep.org; Wed, 25 Nov 2015 22:01:33 +0000 Received: from mail-wm0-f41.google.com ([74.125.82.41]) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES128-GCM-SHA256:128) (Exim 4.86) (envelope-from ) id 1a1i71-0005er-Gv for rsgb_lf_group@blacksheep.org; Wed, 25 Nov 2015 22:01:32 +0000 Received: by wmec201 with SMTP id c201so5786138wme.0 for ; Wed, 25 Nov 2015 14:00:07 -0800 (PST) X-DKIM-Result: Domain=gmail.com Result=Good and Known Domain DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:date:message-id:subject:from:to:content-type; bh=dYip+FVPcVWELkp3e5QTc2LbZYTKWcTcH+qycbTS2ro=; b=w58Onmtq3flAHzip/jvcNM8JyECW1nmS6Oi4+dM/LoSiUYCl/qTMgTVyfvRDh1HoyJ wyPQPGKhwCgPpQ4MPfMXErp+RBGD+Gjl/0M3RqsRdc/l4J5ZiadFqhaZeZSBi6A3b3nH wVcoND6csINUY60+1FyOpk/izxGNPdcs6hhYYUyJUjF2S54FehQdnwXUcffzrt/rkR9s hZRwSdDFL0S6oFHd/+aX4HNxvQzT+/dH21+u6iZVx5vs262nRxpS4bGUtg9mncJHnh6H d3hG6t5J4+4mhBH8ecS+1uVTdZXUnVzwdisGydxIpLu55GlFYZKK9aLMC+MzPQzPKFlr AZxQ== MIME-Version: 1.0 X-Received: by 10.28.91.83 with SMTP id p80mr7413390wmb.87.1448488807319; Wed, 25 Nov 2015 14:00:07 -0800 (PST) Received: by 10.28.130.139 with HTTP; Wed, 25 Nov 2015 14:00:07 -0800 (PST) Date: Wed, 25 Nov 2015 22:00:07 +0000 Message-ID: From: Andy Talbot To: rsgb_lf_group@blacksheep.org, rsgb_lf_group@yahoogroups.co.uk X-Scan-Signature: 5f132ffce194fb93f2267a462d849f2b Subject: LF: Alternative high resolution frequency source for LF Content-Type: multipart/alternative; boundary=001a11443810d24ff305256494c7 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-Scanned-By: MIMEDefang 2.56 on 10.1.3.10 Status: O X-Status: X-Keywords: X-UID: 5323 --001a11443810d24ff305256494c7 Content-Type: text/plain; charset=UTF-8 Although DDS sources seem to more-or-less dominate where high resolution / accuracy is needed, there is another route that could be worth investigating: Fractional-N synthesis with addtional dividers. For example, the LMX2541 with a 10MHz reference phase comparator input will generate steps as low as 2.38Hz at its minimum internal VCO frequency of 2.2GHz. A programmable output divider goes to divide-by 63, allowing steps of 0.038Hz at 35MHz . Add a single chip binary divider of 256 (for the 137kHz band) and you're down to 150uHz steps - which are completely deterministic. Since phase noise and Fract-N sidebands are hardly an issue with this degree of output division, the phase comparator could be operated at a much lower frequency, say 500kHz, allowing steps of lower than 10uHz. Which is a significantly higher resolution than the 2.3mHz steps the traditional AD9850 32 bit DDS offers. I've used these Fract-N devices extensively at microwaves, see http://www.g4jnt.com/LMX2541_Synth_Module.pdf , but haven't yet turned one into an LF exciter Andy G4JNT --001a11443810d24ff305256494c7 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
Although DDS sources seem to more-or-less dominate where h= igh resolution / accuracy is needed, there is another route that could be w= orth investigating: =C2=A0 Fractional-N synthesis with addtional dividers.<= div>
For example, the LMX2541 =C2=A0with a =C2=A010MHz refere= nce =C2=A0phase comparator input will generate steps as low as 2.38Hz at it= s minimum internal VCO frequency of 2.2GHz.=C2=A0 A programmable output div= ider goes to divide-by 63, allowing steps of 0.038Hz at 35MHz .=C2=A0 Add a= single chip binary divider of 256 (for the 137kHz band) =C2=A0and you'= re down to 150uHz steps - which are completely deterministic.
Since phase noise and Fract-N sidebands are hardly an issue wit= h this degree of output division, the phase comparator could be operated at= a much lower frequency, say 500kHz, allowing steps of =C2=A0lower than 10u= Hz. =C2=A0 Which is a significantly higher resolution than the 2.3mHz steps= the traditional AD9850 32 bit DDS offers.=C2=A0

I= 've used these Fract-N devices extensively at microwaves, =C2=A0see http://www.g4jnt.com= /LMX2541_Synth_Module.pdf , =C2=A0 =C2=A0but haven't yet turned one= into an LF exciter

Andy =C2=A0G4JNT
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