Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-df04.r1000.mx.aol.com (Internet Inbound) with ESMTP id 84B703800012F; Tue, 16 Aug 2011 07:59:06 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1QtIHD-0001YT-Hg for rs_out_1@blacksheep.org; Tue, 16 Aug 2011 12:57:47 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1QtIHD-0001YK-0x for rsgb_lf_group@blacksheep.org; Tue, 16 Aug 2011 12:57:47 +0100 Received: from mail-pz0-f42.google.com ([209.85.210.42]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1QtIH9-0002Jb-Hc for rsgb_lf_group@blacksheep.org; Tue, 16 Aug 2011 12:57:46 +0100 Received: by pzk37 with SMTP id 37so4517385pzk.1 for ; Tue, 16 Aug 2011 04:57:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; bh=NR5PIxhTPCzig6unrckdXc0Aket1f/ZuxA4bCFBx5mA=; b=UtyrAiAeDvAZeDemASGnyI4CGhSNBP5snPPQYuTwoNsoAQcRjZw4Ah+kxAITHRfUZn GRwfuNfG3E82ey935e0btq+UhQFcpn01YP3V56qtDwepo4Ggwj8b/LAKB4TsnNT/IxTc tX/dwmJyKer9aXMX0SjmOHVjeQ/gleayW6fIU= MIME-Version: 1.0 Received: by 10.142.2.28 with SMTP id 28mr2523479wfb.392.1313495856078; Tue, 16 Aug 2011 04:57:36 -0700 (PDT) Received: by 10.142.188.7 with HTTP; Tue, 16 Aug 2011 04:57:36 -0700 (PDT) In-Reply-To: <51E78B0C619E4A90B8BBFCEDC5233A38@JimPC> References: <4E4A4134.4060007@kabelmail.de> <51E78B0C619E4A90B8BBFCEDC5233A38@JimPC> Date: Tue, 16 Aug 2011 12:57:36 +0100 Message-ID: From: Roger Lapthorn To: rsgb_lf_group@blacksheep.org X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: Re: LF: Re: Ferrite Loops Content-Type: multipart/alternative; boundary=00504502ad51ea5e5504aa9e156b 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-SCORE: 0:2:453260448:93952408 X-AOL-SCOLL-URL_COUNT: 0 X-AOL-SCOLL-AUTHENTICATION: mail_rly_antispam_dkim-d291.1 ; domain : gmail.com DKIM : pass x-aol-sid: 3039ac1d40d84e4a5b890f9d X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none --00504502ad51ea5e5504aa9e156b Content-Type: text/plain; charset=ISO-8859-1 Hi Jim (et al) *Ferrite rods as 5-20W TX loading coils?* As long as the ferrite doesn't saturate am I right in thinking that the use of ferrite rods as coil formers for 137 and 500kHz is basically "a good idea"? >From personal experience with 5W this worked well at 500kHz so I assume that the idea could be translated to 136kHz if using separate rods for each 500uH of inductance so the cores of each do not saturate. Am I right in thinking that if you bundle x cores together (in parallel) the core will saturate at x times the power? Making a ferrite rod based variometer would be straightforward - PVC tube with cores sliding together lengthwise for example. Engineering large air-spaced loading coils is quite a feat whereas making up, for example, 8-10 separate ferrite coils with a range of taps on each is quite easy (and small). Less wire would be needed so the losses in the coils would be lower compared with the air-spaced equivalent. Is there mileage in this, say up to 15-20W RF? 73s Roger G3XBM On 16 August 2011 11:53, James Moritz wrote: > Dear Tom, LF Group, > > what do you think about an array of many parallel mounted ferrite rods, >> each of them carrying only a few windigs, all windings connected in series >> (and then perhaps tuned) and the rods arraged in such a way that the >> individual apertures dont touch? Or will this lead to the dimensions of a >> comparable air loop ;-) ? >> > > I am sure this would work, but I think you have also identified the > limitation ;-) Fundamentally, if the signal has a particular power density > at the receive site, the antenna must intercept the signal from a certain > aperture area in order to deliver a certain power to the receiver. So there > is a limit to how small it can practically be, although the actual shape can > vary to obtain the same aperture - one could make a rough comparison between > the short, wide loop vs. the long, thin ferrite rod, and a long yagi vs. a > broadside array of dipoles. > > I think an array of ferrite rods might be attractive in some circumstances > - for instance, you could have numerous small rods stacked vertically, to > produce a "ferrite rod vertical" with a small turning circle but a > relatively large effective area. > > Cheers, Jim Moritz > 73 de M0BMU > > > > -- http://g3xbm-qrp.blogspot.com/ http://www.g3xbm.co.uk http://www.youtube.com/user/g3xbm https://sites.google.com/site/sub9khz/ --00504502ad51ea5e5504aa9e156b Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Hi Jim (et al)

Ferrite rods as 5-20W TX loading coils?
As long as the ferrite doesn't saturate am I right in thinking that th= e use of ferrite rods as coil formers for 137 and 500kHz is basically "= ;a good idea"?=A0

From personal experience with 5W this worked well at 500kHz so I assume= that the idea could be translated to 136kHz if using separate rods for eac= h 500uH of inductance so the cores of each do not saturate. Am I right in t= hinking that if you bundle x cores together (in parallel) the core will sat= urate at x times the power? Making a ferrite rod based variometer would be = straightforward - PVC tube with cores sliding together lengthwise for examp= le.

Engineering large air-spaced loading coils is quite a feat whereas maki= ng up, for example, 8-10 separate ferrite coils with a range of taps on eac= h is quite easy (and small). Less wire would be needed so the losses in the= coils would be lower compared with the air-spaced equivalent.

Is there mileage in this, say up to 15-20W RF?

73s
Roger G3XB= M

On 16 August 2011 11:53, James Moritz <= span dir=3D"ltr"><james.moritz@btopenworld.com> wrote:
Dear Tom, LF Group,

what do you think about an array of many parallel mounted ferrite rods, eac= h of them carrying only a few windigs, all windings connected in series (an= d then perhaps tuned) and the rods arraged in such a way that the individua= l apertures dont touch? Or will this lead to the dimensions of a comparable= air loop ;-) ?

I am sure this would work, but I think you have also identified the limitat= ion ;-) Fundamentally, if the signal has a particular power density at the = receive site, the antenna must intercept the signal from a certain aperture= area in order to deliver a certain power to the receiver. So there is a li= mit to how small it can practically be, although the actual shape can vary = to obtain the same aperture - one could make a rough comparison between the= short, wide loop vs. the long, thin ferrite rod, and a long yagi vs. a bro= adside array of dipoles.

I think an array of ferrite rods might be attractive in some circumstances = - for instance, you could have numerous small rods stacked vertically, to p= roduce a "ferrite rod vertical" with a small turning circle but a= relatively large effective area.

Cheers, Jim Moritz
73 de M0BMU






--
http://g3xbm-qrp.blogspot.com/http://www.g3xbm.co.u= k
http://www.= youtube.com/user/g3xbm
https://sites.google.com/site/sub9khz/

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