Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-mp03.r1000.mx.aol.com (Internet Inbound) with ESMTP id 3B8DC38000092; Thu, 29 Sep 2011 05:07:50 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1R9CZw-00036b-3Z for rs_out_1@blacksheep.org; Thu, 29 Sep 2011 10:06:52 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1R9CZv-00036S-DE for rsgb_lf_group@blacksheep.org; Thu, 29 Sep 2011 10:06:51 +0100 Received: from nm6-vm0.bullet.mail.ird.yahoo.com ([77.238.189.210]) by relay1.thorcom.net with smtp (Exim 4.63) (envelope-from ) id 1R9CZt-00038A-Oi for rsgb_lf_group@blacksheep.org; Thu, 29 Sep 2011 10:06:51 +0100 Received: from [77.238.189.234] by nm6.bullet.mail.ird.yahoo.com with NNFMP; 29 Sep 2011 09:06:43 -0000 Received: from [212.82.108.251] by tm15.bullet.mail.ird.yahoo.com with NNFMP; 29 Sep 2011 09:06:43 -0000 Received: from [127.0.0.1] by omp1016.mail.ird.yahoo.com with NNFMP; 29 Sep 2011 09:06:43 -0000 X-Yahoo-Newman-Property: ymail-3 X-Yahoo-Newman-Id: 779820.75877.bm@omp1016.mail.ird.yahoo.com Received: (qmail 85244 invoked by uid 60001); 29 Sep 2011 09:06:43 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yahoo.com; s=s1024; t=1317287203; bh=VpwgqDJhmHoelzgEVd2HiIN0EVkO6WI8yNaq89zxIEs=; h=X-YMail-OSG:Received:X-Mailer:References:Message-ID:Date:From:Reply-To:Subject:To:In-Reply-To:MIME-Version:Content-Type; b=cWnkSBvQtPTbgMMLyi1UhHlWdM5mZCRMWOwx9muEhftKS9ciuLXn1e/Cooqv4JrrYMTbDhEZqUGmM//0c1Hcb9i0vcDzERouJs1as7ssloarPayn3GBJyMXCOAS91YsJqq/IMLY5xmYslK1lofVvG4b+6gZ2Z+a8KPsoIPjvRd0= 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=znpo8cGD3OALPkLo/CgC0F/DZSNyfTfQsEWyfOKLewMjOuREZRTr7rdXb/9m5keXLIXqrVbOdF2ohJCYa9OAMXv02G68WyHckVsFETy+EGbwBA9JXFt5SRDHu7y8u3fGkMqRSQOx0fDyVD10nXDxJ1XYE76pm5NRqVo37ANWBck=; X-YMail-OSG: gS5r_IkVM1lT8jqeA6tCJ_wdeen8qozjczA8DpLc2JdXDux PITzr7dFcDX2a9FZc97edW27bEyvqu4yi7Q57lCfsEpFXsEMz0xEcwpCYs_D Z_jNx9pdkF5c8n8jbkFDGW0WguFoEvLEHARSRDlquSQIyOZeWGt1cPcFn6cW 9Mav0pvNWmGxDAVvJYEbdu7T_KZoo4r9gW4.CZJ11qUfv9BAS5Mep9NZykTM 06Lz0IpPrmtbgwt9SAqdtaOQAqWkSG905_GQ3Os.luSlInKbP13MYwhpwLv8 D4QOR97p74ZB.zeFKlpoqnwfkJVHE1DlDEjERcav0HoKiBr7mMUOLBvGbb3B c9F9gUKOOT3Xj4TtwJodp Received: from [151.99.187.181] by web29516.mail.ird.yahoo.com via HTTP; Thu, 29 Sep 2011 10:06:43 BST X-Mailer: YahooMailWebService/0.8.114.317681 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> <1317076720.22768.YahooMailNeo@web29509.mail.ird.yahoo.com> <1317077173.13177.YahooMailNeo@web29509.mail.ird.yahoo.com> <1317119515.35504.YahooMailNeo@web29502.mail.ird.yahoo.com> <97A4CD4629F94A90A7F5AFD6E2A17E73@JimPC> Message-ID: <1317287203.84598.YahooMailNeo@web29516.mail.ird.yahoo.com> Date: Thu, 29 Sep 2011 10:06:43 +0100 (BST) From: Daniele Tincani To: "rsgb_lf_group@blacksheep.org" In-Reply-To: <97A4CD4629F94A90A7F5AFD6E2A17E73@JimPC> 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: My first ferrite experiments Content-Type: multipart/alternative; boundary="-1036887149-737691782-1317287203=:84598" 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: 0:2:457035168:93952408 X-AOL-SCOLL-URL_COUNT: 0 X-AOL-SCOLL-AUTHENTICATION: mail_rly_antispam_dkim-m221.1 ; domain : yahoo.com DKIM : fail x-aol-sid: 3039ac1dc1474e8435663eb5 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none ---1036887149-737691782-1317287203=:84598 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable Hello Jim,=0A=A0=0Athanks a lot for your helpful advice. However, as I'm sh= ort with free time (because of job & family duties :-)), I'm afraid I will = have to stay with current build, that is three stacked 10mm x 200mm rods in= a 16mm-diameter PVC tube (about 60cm long), which also acts as the mechani= cal support for the rods and for the coil. The coil distance from the centr= al rod is then about 3mm. I wound 70 turns of 175/46 litz wire (doing my be= st to obtain a good winding) and my estimation of resulting inductance - ba= sed on measured frequency of resonance at min value=A0and max value of the = var cap - is around 670uH.=0AMy next steps will be to give a more stable me= chanical arrangement to the set, with short wires and soldered connections = in place of crocodile clips of course and then perform new Q measurements. = The shield will be added later, if required.=0AThe plan is to connect the L= C pair to a Mike Tuggle's homodyne mainly for NDB chasing. I discarded othe= r possibilities (e.g. using it as a tuned loop antenna for a portable recei= ver) due to need to operate frequently on two tuning knobs, which can be ra= pidly become a bit boring.=0A=A0=0ABest regards=0ADaniele=0A=A0=0A=0ADa: Ja= mes Moritz =0AA: rsgb_lf_group@blacksheep.org= =0AInviato: Gioved=EC 29 Settembre 2011 10:35=0AOggetto: LF: Re: My first f= errite experiments=0A=0ADear Daniele, LF Group,=0A=0AI would agree with oth= ers that the presence of the screen is reducing the Q in your ferrite rod. = One must also be cautious about the possible effects of interconnecting wir= es, dielectric losses in wire insulation, the effect of the table and other= nearby objects, etc. Also, loading by the scope probe is occasionally supr= isingly high, where the resonant impedance of the rod antenna is high.=0A= =0AFor small antennas like this, it is important to maximise the unloaded Q= , since achieving adequate signal-to-noise ratio is the primary function of= a receiving antenna and the SNR of the antenna itself is directly related = to Qu. Screening an H-field antenna against electric field pick-up might be= important (especially where the antenna is used for direction finding). Bu= t it will inevitably reduce Q to some extent due to eddy current losses and= the effect of additional distributed capacitance. Therefore there is a tra= de-off between reducing unwanted E-field pick-up, etc, and degrading the se= nsitivity. Similarly, spacing the winding from the ferrite rod and/or the a= luminium screen may reduce some sources of loss, but will lead to increased= winding resistance due to the greater length of wire needed for each turn,= so it could be an advantage or a disadvantage.=0A=0ASo it is important to = know if the screening and winding arrangements cause a large reduction in Q= - I would suggest doing a simple baseline test by winding some wire direct= ly onto one of your ferrite rods, without any screening or additional insul= ation, and see how the Q results compare.=0A=0ACheers, Jim Moritz=0A73 de M= 0BMU ---1036887149-737691782-1317287203=:84598 Content-Type: text/html; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable
Hello Jim,
 
thanks a lot for you= r helpful advice. However, as I'm short with free time (because of job &= ; family duties :-)), I'm afraid I will have to stay with current build, th= at is three stacked 10mm x 200mm rods in a 16mm-diameter PVC tube (about 60= cm long), which also acts as the mechanical support for the rods and for th= e coil. The coil distance from the central rod is then about 3mm. I wound 7= 0 turns of 175/46 litz wire (doing my best to obtain a good winding) and my= estimation of resulting inductance - based on measured frequency of resona= nce at min value and max value of the va= r cap - is around 670uH.
My next steps will b= e to give a more stable mechanical arrangement to the set, with short wires= and soldered connections in place of crocodile clips of course and then pe= rform new Q measurements. The shield will be added later, if required.
The plan is to conne= ct the LC pair to a Mike Tuggle's homodyne mainly for NDB chasing. I discar= ded other possibilities (e.g. using it as a tuned loop antenna for a portab= le receiver) due to need to operate frequently on two tuning knobs, which c= an be rapidly become a bit boring.
 
Best regards<= /div>
Daniele
 

Da: James Moritz <james.moritz@btopenworld.com>
A: rsgb_lf_group@blacksheep.org
<= SPAN style=3D"FONT-WEIGHT: bold">Inviato: Gioved=EC 29 Settembre= 2011 10:35
Oggetto: LF:= Re: My first ferrite experiments

Dear Daniele, LF Group,
=
I would agree with others that the presence of the screen is reducing t= he Q in your ferrite rod. One must also be cautious about the possible effe= cts of interconnecting wires, dielectric losses in wire insulation, the eff= ect of the table and other nearby objects, etc. Also, loading by the scope probe is o= ccasionally suprisingly high, where the resonant impedance of the rod anten= na is high.

For small antennas like this, it is important to maximis= e the unloaded Q, since achieving adequate signal-to-noise ratio is the pri= mary function of a receiving antenna and the SNR of the antenna itself is d= irectly related to Qu. Screening an H-field antenna against electric field = pick-up might be important (especially where the antenna is used for direct= ion finding). But it will inevitably reduce Q to some extent due to eddy cu= rrent losses and the effect of additional distributed capacitance. Therefor= e there is a trade-off between reducing unwanted E-field pick-up, etc, and = degrading the sensitivity. Similarly, spacing the winding from the ferrite = rod and/or the aluminium screen may reduce some sources of loss, but will l= ead to increased winding resistance due to the greater length of wire needed for each turn, so it could be an advantage or a disadvantage.<= BR>
So it is important to know if the screening and winding arrangements= cause a large reduction in Q - I would suggest doing a simple baseline tes= t by winding some wire directly onto one of your ferrite rods, without any = screening or additional insulation, and see how the Q results compare.
<= BR>Cheers, Jim Moritz
73 de M0BMU



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