Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-dl01.r1000.mx.aol.com (Internet Inbound) with ESMTP id 2CE643800173A; Tue, 30 Aug 2011 10:40:01 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1QyPSz-0007gO-4j for rs_out_1@blacksheep.org; Tue, 30 Aug 2011 15:39:05 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1QyPSy-0007gF-GC for rsgb_lf_group@blacksheep.org; Tue, 30 Aug 2011 15:39:04 +0100 Received: from nm14-vm0.bullet.mail.sp2.yahoo.com ([98.139.91.246]) by relay1.thorcom.net with smtp (Exim 4.63) (envelope-from ) id 1QyPSw-0006ze-4y for rsgb_lf_group@blacksheep.org; Tue, 30 Aug 2011 15:39:04 +0100 Received: from [98.139.91.62] by nm14.bullet.mail.sp2.yahoo.com with NNFMP; 30 Aug 2011 14:38:53 -0000 Received: from [98.139.91.14] by tm2.bullet.mail.sp2.yahoo.com with NNFMP; 30 Aug 2011 14:38:53 -0000 Received: from [127.0.0.1] by omp1014.mail.sp2.yahoo.com with NNFMP; 30 Aug 2011 14:38:53 -0000 X-Yahoo-Newman-Property: ymail-3 X-Yahoo-Newman-Id: 410452.53897.bm@omp1014.mail.sp2.yahoo.com Received: (qmail 96375 invoked by uid 60001); 30 Aug 2011 14:38:52 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yahoo.com; s=s1024; t=1314715132; bh=SdsCm2mUQ7buSl8lTnyEqcsornu8K2IPoJ6i9ZnSevI=; h=X-YMail-OSG:Received:X-Mailer:References:Message-ID:Date:From:Reply-To:Subject:To:In-Reply-To:MIME-Version:Content-Type; b=g3NUJSFLqiyQZKEb0Lp7cGhTfR66Y55lsJJ0s60ELnMK0/c0QxNw5FKcRK1EeoZjEfIe8vCq/jgXAx1bITsgAqX8qZTT9EsbU6hYU/WcFMa5FJAirm+0i6q+/i/FZ8aVEDNPBl1ttQOu8o2xqpv5DZw/lb+RfWvjkOz1O7o530g= DomainKey-Signature:a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; h=X-YMail-OSG:Received:X-Mailer:References:Message-ID:Date:From:Reply-To:Subject:To:In-Reply-To:MIME-Version:Content-Type; b=AFz8uG48pa4YaaQjSU6SgolUmWUq8qhVyLoEjiOClbwAzkCTV1jFgBy8Z3rWPIerzue9yhFFULR+k0Ayg7c3gtCCK8qnf9G/0ya6CAwZGoF301V8YOkfQ4fzcMXjN6vEjbsqFwNw7nZNN0rrw+WppbgBvcd2eNaAUwP54j3B1ig=; X-YMail-OSG: iMoZRcsVM1kvcaxogdj9i89rcOxs_vlgpo_Hz636lOakPDa 6eocy2VRGq4e9zgItPnhgwdcQ0_onaWYHymUNvs8tQdOnZzwl8z57U68v0T7 GeccTTKkH41Rr2heQBDODKn1OPESUQTpan22TPjRT6e00S7T.V7qzlcrgaAB ZDCraD38jlWFBxnkzyW91lQs1ItDudDv6dG7Lj8ehu5tRYb5aImB8J.AQcVL eECjZx4588GYG.HQ9bMU1Y3v_e0R3JtqUd_sfnhib4DopFTUpedV3Ehl61Xs xxe6pxTEc9R2Ig3ZOgQrj7Fa.p4XyFSCy7PBs6mZqldTlI4rBSmLbQi4d5A4 FQY7jk7nYmHscMlqHjBosv6cq9tEaUnH0bAjo3f1EdHHhbWsU4TUTDaUpnid vZIOR1M2XaTPD.VWQrL0rLusB Received: from [151.99.187.181] by web111917.mail.gq1.yahoo.com via HTTP; Tue, 30 Aug 2011 07:38:52 PDT X-Mailer: YahooMailWebService/0.8.113.315625 References: <16BC8B3CA8672445BC2A29B4C14A26D4379ED2AAB4@exlnmb01.eur.nsroot.net> <4DF9EFD1.5010208@iup.uni-heidelberg.de> <1313780109.51443.YahooMailNeo@web111907.mail.gq1.yahoo.com> <9CD1E11E8BC9402CB4AECECAC4088443@JimPC> <1314394178.5030.YahooMailNeo@web111905.mail.gq1.yahoo.com> <1314641183.5605.YahooMailNeo@web111910.mail.gq1.yahoo.com> <4E5CBC9A.5020900@iup.uni-heidelberg.de> <1314705226.37125.YahooMailNeo@web111901.mail.gq1.yahoo.com> <4E5CF192.3040905@legal-medicine.de> Message-ID: <1314715132.88047.YahooMailNeo@web111917.mail.gq1.yahoo.com> Date: Tue, 30 Aug 2011 07:38:52 -0700 (PDT) From: Daniele Tincani To: "rsgb_lf_group@blacksheep.org" In-Reply-To: <4E5CF192.3040905@legal-medicine.de> MIME-Version: 1.0 DomainKey-Status: good (testing) X-Spam-Score: 1.4 (+) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001,HTML_TINY_FONT=1.425 Subject: Re: LF: Re: Ferrite wideband antennas? Content-Type: multipart/alternative; boundary="0-985689999-1314715132=:88047" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=1.0 required=5.0 tests=FORGED_YAHOO_RCVD,HTML_20_30, HTML_MESSAGE,TO_ADDRESS_EQ_REAL 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-SCORE: 0:2:483306336:93952408 X-AOL-SCOLL-URL_COUNT: 0 X-AOL-SCOLL-AUTHENTICATION: mail_rly_antispam_dkim-m004.2 ; domain : yahoo.com DKIM : fail x-aol-sid: 3039ac1d4acf4e5cf6417ae4 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none --0-985689999-1314715132=:88047 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable =A0=0AHello Peter,=0A=A0=0Avery helpful information! Thanks a lot.=0A=A0=0A= BTW, I downloaded the Pelgrum's work days ago. I will read it carefully bef= ore starting my loop construction.=0A=A0=0ABest regards=0ADaniele=0A=A0=0A= =0AFrom: pws =0ATo: rsgb_lf_group@blacksheep.org=0AS= ent: Tuesday, August 30, 2011 4:20 PM=0ASubject: Re: LF: Re: Ferrite wideba= nd antennas?=0A=0AHi Daniele,=0A=0AYou wrote:=0A> ...=0A> Yesterday evening= a purchased a bunch of 7 x MU400HH ferrites (10mm x 200mm each) on eBay, p= lanning to join them together "in parallel" to form a fatter rod, no idea i= f it will be a good choice but let's play with this new toy ;-) Meanwhile I= 'm collecting ideas and hints from the web about construction (shielding, c= omputing/measuring parameters, ect.). Projects are stacking as usual :-)=0A= > ...=0A=0AThese rods are working fine even at VLF. But according to my own= experiences in the late 90th bundling is not worth the effort. Two tight (= !) stacked 15cm rods achieved better SNR compared to a bundle of 7 rods.=0A= =0APELGRUM (2006) confirms these findings:=0A"...=0AThe rod-length has a la= rger influence on the noise-performance than the rod diameter. Therefore, i= n weight-limited applications, rod length is preferred over rod diameter. H= owever, this may conflict with the requirements of volume-limited applicati= ons, such as mobile/handheld.=0A..."=0Aand:=0A"...=0AIn applications where = the antenna size is limited, it can be beneficial to use multiple small fer= rite rods instead of a single larger rod...=0A...it can be concluded that t= wo 10 cm rods experience virtually no mutual=0Acoupling when placed 10 cm a= part, and therefore, result in a 3 dB increase in SNR compared to a single = 10 cm rod.=0A..."=0A=0AAnd for the coil length:=0A"...=0Athe best noise per= formance is achieved for a fully wound rod: an=0Aimprovement in SNR of appr= oximately 2.2 dB is obtained when a fully wound rod is used instead of a na= rrow coil at the center of the rod.=0A..."=0A=0ASource: Wouter J. Pelgrum, = "New Potential of Low-Frequency Radionavigation in the 21st Century", Delft= , November 2006=0A=0AThese are empirically obtained findings!=0A=0AAccordin= g to that and what I know from professionals (submarine) stacking works fin= e up to length/diameter ratios of approx. 60. Above that ratio bundling may= be an option. Of course the challenge is to fix those stacked rods in plac= e tightly...=0A=0APeter, df3lp --0-985689999-1314715132=:88047 Content-Type: text/html; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable
 
Hello Peter,<= /div>
 
very helpful informa= tion! Thanks a lot.
 
BTW, I downloaded th= e Pelgrum's work days ago. I will read it carefully before starting my loop= construction.
 
Best regards<= /div>
Daniele
 

From:= pws <pws@legal-medicine.de>
To: rsgb_lf_group@blacksheep.org
Sent: Tuesday, August 30, 2011 4:20 PM
Subject: Re: LF: Re: Ferrite = wideband antennas?

Hi Daniele,

You wrote:
> ...<= BR>> Yesterday evening a purchased a bunch of 7 x MU400HH ferrites (10mm= x 200mm each) on eBay, planning to join them together "in parallel" to for= m a fatter rod, no idea if it will be a good choice but let's play with thi= s new toy ;-) Meanwhile I'm collecting ideas and hints from the web about constructi= on (shielding, computing/measuring parameters, ect.). Projects are stacking= as usual :-)
> ...

These rods are working fine even at VLF. B= ut according to my own experiences in the late 90th bundling is not worth t= he effort. Two tight (!) stacked 15cm rods achieved better SNR compared to = a bundle of 7 rods.

PELGRUM (2006) confirms these findings:
"...<= BR>The rod-length has a larger influence on the noise-performance than the = rod diameter. Therefore, in weight-limited applications, rod length is pref= erred over rod diameter. However, this may conflict with the requirements o= f volume-limited applications, such as mobile/handheld.
..."
and:
= "...
In applications where the antenna size is limited, it can be benefi= cial to use multiple small ferrite rods instead of a single larger rod......it can be concluded that two 10 cm rods experience virtually no mutual
coupling when placed 10 cm apart, and therefore, result in a 3 d= B increase in SNR compared to a single 10 cm rod.
..."

And for th= e coil length:
"...
the best noise performance is achieved for a full= y wound rod: an
improvement in SNR of approximately 2.2 dB is obtained w= hen a fully wound rod is used instead of a narrow coil at the center of the= rod.
..."

Source: Wouter J. Pelgrum, "New Potential of Low-Frequ= ency Radionavigation in the 21st Century", Delft, November 2006

Thes= e are empirically obtained findings!

According to that and what I kn= ow from professionals (submarine) stacking works fine up to length/diameter= ratios of approx. 60. Above that ratio bundling may be an option. Of cours= e the challenge is to fix those stacked rods in place tightly...

Pet= er, df3lp



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