Return-Path: Received: from mtain-df02.r1000.mx.aol.com (mtain-df02.r1000.mx.aol.com [172.29.64.214]) by air-da07.mail.aol.com (v129.4) with ESMTP id MAILINDA072-86174d6e7232229; Wed, 02 Mar 2011 11:37:06 -0500 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-df02.r1000.mx.aol.com (Internet Inbound) with ESMTP id B3CED38000214; Wed, 2 Mar 2011 11:37:04 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Pup2C-0007bd-Pt for rs_out_1@blacksheep.org; Wed, 02 Mar 2011 16:36:20 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1Pup2B-0007bP-W3 for rsgb_lf_group@blacksheep.org; Wed, 02 Mar 2011 16:36:19 +0000 Received: from mail-iw0-f171.google.com ([209.85.214.171]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1Pup27-0000ob-UI for rsgb_lf_group@blacksheep.org; Wed, 02 Mar 2011 16:36:19 +0000 Received: by iwr19 with SMTP id 19so139561iwr.16 for ; Wed, 02 Mar 2011 08:36:10 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:in-reply-to:references:date :message-id:subject:from:to:content-type; bh=2X1g7eZ2UTZHaFVljAo4j9nl16PG+E/XRiFUq7r7J0g=; b=gnztZKpj66G9bUlh3qJ+k+kbCWVnuzZEQrRHmqbAdMj5MuvPwJIf2JZ9rn1EFpx2SC wVkR8ZQJQ0f0uCCYant+6290cXG7aTV6AKHPnFsnMtQNI2rtDft5bItZ+8aTYBKU9IoK DSlPkq5813rm62V8YWF652irhL86jAkEw6w6U= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; b=QS3ThM2NI+76QWlB7cgJ7J0tRcTcibv4Ab7S1XMJthnzHrFJ7fpYgw5DvBoOr2hrOH Bm/7rbRj5fI30fEnMnZHNspRlMRoBBu/NFktWLwz/noSc0ym8Mjhw2aXNf3d09WEoTlb M3AHNcRvF6XZ1zgCRncJsQ6upUndE3qdMvbZw= MIME-Version: 1.0 Received: by 10.231.25.91 with SMTP id y27mr111996ibb.41.1299083769712; Wed, 02 Mar 2011 08:36:09 -0800 (PST) Received: by 10.231.205.196 with HTTP; Wed, 2 Mar 2011 08:36:09 -0800 (PST) In-Reply-To: <99441.33028.qm@web28108.mail.ukl.yahoo.com> References: <80823E80F3B94DCEB2B95EA9A57C72C4@JimPC> <99441.33028.qm@web28108.mail.ukl.yahoo.com> Date: Wed, 2 Mar 2011 16:36:09 +0000 Message-ID: From: Andy Talbot To: rsgb_lf_group@blacksheep.org DomainKey-Status: good (testing) X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: Re: LF: Re: WRC-2012 proposal for 'near' 500kHz band(s) Content-Type: multipart/alternative; boundary=001517740560a0919f049d82825c X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.1 required=5.0 tests=HTML_FONT_BIG,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-aol-global-disposition: G X-AOL-SCOLL-AUTHENTICATION: mail_rly_antispam_dkim-d012.1 ; domain : gmail.com DKIM : pass x-aol-sid: 3039ac1d40d64d6e7230425d X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none X-Mailer: Unknown (No Version) --001517740560a0919f049d82825c Content-Type: text/plain; charset=ISO-8859-1 Or help me programme in a lower divider ratio into the DDS 'JNT On 2 March 2011 16:20, M0FMT wrote: > > Wonderfull! and maybe you can help me grind all my crystals lower in > frequency as well Jim. > > 73 es GL Pete M0FMT IO91UX > > > ------------------------------ > *From:* James Moritz > *To:* rsgb_lf_group@blacksheep.org > *Sent:* Wed, 2 March, 2011 15:43:25 > *Subject:* LF: Re: WRC-2012 proposal for 'near' 500kHz band(s) > > Dear David, LF Group, > > Having poked around inside quite a few radios over the years, I think > 465/470kHz IFs were common in the days of discrete transistors and tuned IF > transformers, but are mostly ancient history now. Most of the more modern > broadcast radios use either 455kHz or 450kHz - the former being the default > centre frequency for ceramic filters, the latter especially for radios with > PLL synthesisers (it works out quite nicely with a 4.500MHz reference > crystal and 9kHz or 10kHz channel spacings). At least in theory, the more > modern cheap broadcast radios should have better IF rejection, since these > single-chip receivers have double balanced mixers, rather than the old > single-ended, self-oscillating, discrete designs. > > The trouble with trying to avoid broadcast RX IF frequencies is that there > is now a wide range to be avoided. With f0 possibly of 450, 455, 465 or > 470kHz, +/- tolerance, and a bandwidth typically around 9kHz, a big chunk of > frequencies from say 440 - 480kHz would have to be excluded on these > grounds. It would be a great waste of spectrum to say these frequencies must > be off-limits for all eternity for the sake of the inadequacies of cheap > receivers used by an ever-decreasing number of listeners. Anyway, these > frequencies always have been used by high power maritime telegraphy, NDBs, > etc. > > Another consideration is that the proposed maritime "super-Navtex" that > might be centerd on 500kHz will inevitably have big powerful transmitters, > using OFDM modulation with several kHz bandwidth. Although the out-of band > emissions for this type of modulation is in principle very small, there will > inevitably be some "spectral re-growth" due to imperfections in transmitter > linearity. The high power levels compared to amateur signals, and wide > coverage areas will mean this would be a major problem for amateurs if we > have to operate on adjacent frequencies (not unlike the problems with > utilities on 136k). There would be no way of convincing the maritime users > they should take remedial action - they would just reply that their > transmitters were fully within spec, which they would be. So if the maritime > proposals go ahead, a large spacing between any amateur band and 500kHz > would be a good thing. I volunteer to help struggling experienced > non-appliance operators to wind a few more turns on their VFO coils if this > happens ;-) > > Cheers, Jim Moritz > 73 de M0BMU > > > > --001517740560a0919f049d82825c Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable
Or help me programme in a lower divider ratio into the DDS
=A0
'JNT
=A0


=A0
On 2 March 2011 16:20, M0FMT = <m0fmt@yahoo.co.uk>= wrote:
=A0
Wonderfull! and=A0maybe you can help me grind all my crystals lower= in frequency as well Jim.
=A0
73 es GL Pete M0FMT IO91UX=20

=
=
From: James Moritz <james.mori= tz@btopenworld.com>
To: = rsgb_lf_group@blacksheep.org
Sent: Wed, 2 March, 2011= 15:43:25
Subject: LF:= Re: WRC-2012 proposal for 'near' 500kHz band(s)

Dear David, LF Group,

Having poked around ins= ide quite a few radios over the years, I think 465/470kHz IFs were common= in the days of discrete transistors and tuned IF transformers, but are mo= stly ancient history now. Most of the more modern broadcast radios use eit= her 455kHz or 450kHz - the former being the default centre frequency for= ceramic filters, the latter especially for radios with PLL synthesisers= (it works out quite nicely with a 4.500MHz reference crystal and 9kHz or= 10kHz channel spacings). At least in theory, the more modern cheap broadc= ast radios should have better IF rejection, since these single-chip receiv= ers have double balanced mixers, rather than the old single-ended, self-os= cillating, discrete designs.

The trouble with trying to avoid broadcast RX IF frequencies is that= there is now a wide range to be avoided. With f0 possibly of 450, 455, 46= 5 or 470kHz, +/- tolerance, and a bandwidth typically around 9kHz, a big= chunk of frequencies from say 440 - 480kHz would have to be excluded on= these grounds. It would be a great waste of spectrum to say these frequen= cies must be off-limits for all eternity for the sake of the inadequacies= of cheap receivers used by an ever-decreasing number of listeners. Anyway= , these frequencies always have been used by high power maritime telegraph= y, NDBs, etc.

Another consideration is that the proposed maritime "super-Navtex= " that might be centerd on 500kHz will inevitably have big powerful= transmitters, using OFDM modulation with several kHz bandwidth. Although= the out-of band emissions for this type of modulation is in principle ver= y small, there will inevitably be some "spectral re-growth" due= to imperfections in transmitter linearity. The high power levels compared= to amateur signals, and wide coverage areas will mean this would be a maj= or problem for amateurs if we have to operate on adjacent frequencies (not= unlike the problems with utilities on 136k). There would be no way of con= vincing the maritime users they should take remedial action - they would= just reply that their transmitters were fully within spec, which they wou= ld be. So if the maritime proposals go ahead, a large spacing between any= amateur band and 500kHz would be a good thing. I volunteer to help strugg= ling experienced non-appliance operators to wind a few more turns on their= VFO coils if this happens ;-)

Cheers, Jim Moritz
73 de M0BMU


<= /div>

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