Return-Path: Received: from mtain-mg07.r1000.mx.aol.com (mtain-mg07.r1000.mx.aol.com [172.29.96.207]) by air-md05.mail.aol.com (v129.4) with ESMTP id MAILINMD052-8b854c211746311; Tue, 22 Jun 2010 16:04:22 -0400 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mtain-mg07.r1000.mx.aol.com (Internet Inbound) with ESMTP id A8EE5380002AB; Tue, 22 Jun 2010 16:04:17 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1OR9gO-0007RY-Es for rs_out_1@blacksheep.org; Tue, 22 Jun 2010 21:02:56 +0100 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1OR9gN-0007RP-Pa for rsgb_lf_group@blacksheep.org; Tue, 22 Jun 2010 21:02:55 +0100 Received: from mail-bw0-f43.google.com ([209.85.214.43]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1OR9gM-0005eY-C2 for rsgb_lf_group@blacksheep.org; Tue, 22 Jun 2010 21:02:55 +0100 Received: by bwz15 with SMTP id 15so592150bwz.16 for ; Tue, 22 Jun 2010 13:02:53 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=googlemail.com; s=gamma; h=domainkey-signature:mime-version:received:received:in-reply-to :references:date:message-id:subject:from:to:content-type; bh=TEexWn/fvz+eaGUF0isOl7bwUw2PedpM6BQp9TknaC0=; b=C3VJ/+tcZNn/J9uhgmrTvYDn0p8koG3Qlrejt9XL91xuXUXpYs/P50784jhy+CahtI wc67wTJerUCyjoRCBCh/xQ4ERvCnJwqYKjFxwranPxcoR/GZPEBGOo9KO6x0aJBG1N6x tXcsE+w3Nxe/EQ9h3XGhScqlZI3H/mhTX89MA= DomainKey-Signature: a=rsa-sha1; c=nofws; d=googlemail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; b=gICI2xyk+PtfudjOrgrHaZ10pd1YxHihgbV6dfxDbT4wQbR45CjJYZwavxcl3Eum8r qTuV9nDGq2AQMlwqSlOdEUKbAxlIVG8I/cEl606vAy+Dxg+519ZgvkvHeR6SLsLY0sQz biraC9qJsjUAiDWQW9e4om5tbv8klYfRdp/68= MIME-Version: 1.0 Received: by 10.204.161.193 with SMTP id s1mr3147743bkx.16.1277236972630; Tue, 22 Jun 2010 13:02:52 -0700 (PDT) Received: by 10.204.70.141 with HTTP; Tue, 22 Jun 2010 13:02:52 -0700 (PDT) In-Reply-To: References: <000c01cb11dc$2b310020$0401a8c0@xphd97xgq27nyf> <3A2133327AFB454CAC336E25F96F4352@TonyLaptop> <00f301cb1204$27dc76c0$0217aac0@desktop> <5CB3170C92154284B48334F50A8DDD89@IBM7FFA209F07C> <6AEC4DD1A0F04696AB42F2158C87F963@TonyLaptop> Date: Tue, 22 Jun 2010 21:02:52 +0100 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: 137 Revival Content-Type: multipart/alternative; boundary=0003255588660c31c90489a3e81f X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: 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-aol-global-disposition: G X-AOL-SCOLL-AUTHENTICATION: mail_rly_antispam_dkim-d273.2 ; domain : googlemail.com DKIM : pass x-aol-sid: 3039ac1d60cf4c21174112ad X-AOL-IP: 193.82.116.20 X-Mailer: Unknown (No Version) --0003255588660c31c90489a3e81f Content-Type: text/plain; charset=ISO-8859-1 see http://www.g4jnt.com/137tx.pdf for another big one. Andy www.g4jnt.com On 22 June 2010 20:04, James Moritz wrote: > Dear Tony, LF Group, > > What you need for a 136kHz transmitter depends a lot on the antenna it is > to be used with, and what you want to do with it. > > Antenna efficiency is usually low on 136k - a small fraction of a percent > is the norm - and very variable. If you have access to 100 foot high antenna > masts, then you will be able to achieve the 1W ERP limit with probably less > than 100W of TX power. But if you are restricted to "back garden" sized > antennas, you will probably need a kilowatt or more to reach this radiated > power level. If you are restricted to lower powers and small antennas, your > ERP will be well below 1W, although contacts over quite decent distances can > be had with tens of milliwatts ERP. Much lower powers are viable at > relatively short ranges within ground-wave propagation distances. But due to > the low numbers of active stations on the band, this severely limits the > number of contacts that will be possible, so 136k is not really a band for > QRP transmitters, unless you have a huge antenna available. > > For CW operation, transmitter design can be pretty simple - a reasonably > stable frequency source, a class D PA stage, and some way of keying it on > and off. For extreme-narrow-band QRSS use, improved frequency stability is > needed. Usually this means some sort of synthesiser, although simpler means, > such as ceramic resonator based VFOs, are quite viable unless extreme > stability is required. If you are interested in data or other "visual" > modes, it gets a bit more complex, requiring either a home brew modulator > operating at 136k, or a transverter to shift the frequency of an existing > rig. Also, amplitude modulation of the signal is needed for some modes, > which requires either a linear PA, or techniques such as "EER". > > Go to G3YXM's pages at http://www.wireless.org.uk/, and look at the > "Circuits", "Features", and "Build a TX" pages for some ideas. The RSGB > books "LF today", and recent editions of the "Radio Communication Handbook" > contain several transmitter designs. I have written up a 200W multi-mode > transverter design using the EER technique at > http://uk500khz.googlegroups.com/web/EER_Transverter_v3.pdf . There are > some designs for 500kHz transmitters also at > http://groups.google.com/group/uk500khz on the "files" page, which could > be easily adapted to 136kHz with appropriate component changes. Google-ing > for "136kHz transmitter" will get you quite a few results. > > Shoving a lot of power into an antenna that is really too small for the job > is never going to be very reliable or foolproof ... but it is sometimes > quite exciting ;-). The class D designs have become popular because they use > simple circuits and cheap, readily available, switching MOSFETs to achieve a > large output power, but one should be aware that most class D circuits will > try to deliver very high output currents into low impedance loads, which can > lead to damage when the antenna is mis-tuned, as it inevitably sometimes is. > With electrically small elements and large loading coils, antennas are > unavoidably high Q with critical tuning which is easily disturbed. Current > limiting of the DC supply or RF output is very desireable. Class D designs > are very efficient and cool-running during normal operation, but can > dissipate a lot of power when badly mis-matched, so conservative design is > needed for reliability. > > Good luck on 136kHz, hope to see you on the band this winter! > > Cheers, Jim Moritz > 73 de M0BMU > > > > From: owner-rsgb_lf_group@blacksheep.org [mailto: > owner-rsgb_lf_group@blacksheep.org] On Behalf Of Tony Baldwin > Sent: 22 June 2010 11:49 > To: rsgb_lf_group@blacksheep.org > Subject: LF: Re: 137 Revival > > > > I fully intend to be QRV on 137 by the winter. > > On that note, can anyone recommend a reliable foolproof transmitter that > uses easily available components ? > > > > Tony, EI8JK. > > > > > --0003255588660c31c90489a3e81f Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable
see=A0 =A0http://www.g4jnt= .com/137tx.pdf=A0=A0=A0 for another big one.
=A0
On 22 June 2010 20:04, James Moritz <james.moritz@= btopenworld.com> wrote:
Dear Tony, LF Group,

Wh= at you need for a 136kHz transmitter depends a lot on the antenna it is to= be used with, and what you want to do with it.

Antenna efficiency is usually low on 136k - a small fraction of a perc= ent is the norm - and very variable. If you have access to 100 foot high= antenna masts, then you will be able to achieve the 1W ERP limit with pro= bably less than 100W of TX power. But if you are restricted to "back= garden" sized antennas, you will probably need a kilowatt or more to= reach this radiated power level. If you are restricted to lower powers an= d small antennas, your ERP will be well below 1W, although contacts over= quite decent distances can be had with tens of milliwatts ERP. Much lower= powers are viable at relatively short ranges within ground-wave propagati= on distances. But due to the low numbers of active stations on the band,= this severely limits the number of contacts that will be possible, so 136= k is not really a band for QRP transmitters, unless you have a huge antenn= a available.

For CW operation, transmitter design can be pretty simple - a reasonab= ly stable frequency source, a class D PA stage, and some way of keying it= on and off. For extreme-narrow-band QRSS use, improved frequency stabilit= y is needed. Usually this means some sort of synthesiser, although simpler= means, such as ceramic resonator based VFOs, are quite viable unless extr= eme stability is required. If you are interested in data or other "vi= sual" modes, it gets a bit more complex, requiring either a home brew= modulator operating at 136k, or a transverter to shift the frequency of= an existing rig. Also, amplitude modulation of the signal is needed for= some modes, which requires either a linear PA, or techniques such as &quo= t;EER".

Go to G3YXM's pages at http://www.wireless.org.uk/, and look at the "Circ= uits", "Features", and "Build a TX" pages for som= e ideas. The RSGB books "LF today", and recent editions of the= "Radio Communication Handbook" contain several transmitter desi= gns. I have written up a 200W multi-mode transverter design using the EER= technique at http://uk500khz.googlegroups.com/web/EER_Tra= nsverter_v3.pdf . There are some designs for 500kHz transmitters also= at = http://groups.google.com/group/uk500khz on the "files" page,= which could be easily adapted to 136kHz with appropriate component change= s. Google-ing for "136kHz transmitter" will get you quite a few= results.

Shoving a lot of power into an antenna that is really too small for th= e job is never going to be very reliable or foolproof ... but it is someti= mes quite exciting ;-). The class D designs have become popular because th= ey use simple circuits and cheap, readily available, switching MOSFETs to= achieve a large output power, but one should be aware that most class D= circuits will try to deliver very high output currents into low impedance= loads, which can lead to damage when the antenna is mis-tuned, as it inev= itably sometimes is. With electrically small elements and large loading co= ils, antennas are unavoidably high Q with critical tuning which is easily= disturbed. Current limiting of the DC supply or RF output is very desirea= ble. Class D designs are very efficient and cool-running during normal ope= ration, but can dissipate a lot of power when badly mis-matched, so conser= vative design is needed for reliability.

Good luck on 136kHz, hope to see you on the band this winter!

C= heers, Jim Moritz
73 de M0BMU



=A0 From: owner-rsgb_lf_grou= p@blacksheep.org [mailto:owner-rsgb_lf_group@blacksheep.org] On Beha= lf Of Tony Baldwin
=A0 Sent: 22 June 2010 11:49
=A0 To: rsgb_lf_group@blacksheep.org
=A0 Su= bject: LF: Re: 137 Revival



=A0 I fully intend to be QRV on= 137 by the winter.

=A0 On that note, can anyone recommend a reliable foolproof transmitte= r that uses easily available components ?



=A0 Tony, EI8JK.<= br>




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