Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-mk05.r1000.mx.aol.com (Internet Inbound) with ESMTP id 332493800009C; Tue, 16 Aug 2011 08:51:19 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1QtJ65-0001ny-GY for rs_out_1@blacksheep.org; Tue, 16 Aug 2011 13:50:21 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1QtJ64-0001np-Uy for rsgb_lf_group@blacksheep.org; Tue, 16 Aug 2011 13:50:20 +0100 Received: from out1.ip09ir2.opaltelecom.net ([62.24.128.245]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1QtJ61-00043Y-Fo for rsgb_lf_group@blacksheep.org; Tue, 16 Aug 2011 13:50:20 +0100 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: As8AAG5mSk5Ok80o/2dsb2JhbABBlF4DhAGPUniBOwUBAQUIAQEDSQIsAQEDBQIBAxEEAQEKJRQBBBoGFggGEwoBAgIBAYdhArlVhkgEglGEX5VYhwA X-IronPort-AV: E=Sophos;i="4.67,380,1309734000"; d="scan'208,217";a="487508630" Received: from host-78-147-205-40.as13285.net (HELO xphd97xgq27nyf) ([78.147.205.40]) by out1.ip09ir2.opaltelecom.net with SMTP; 16 Aug 2011 13:50:11 +0100 Message-ID: <001601cc5c12$ffe69510$0401a8c0@xphd97xgq27nyf> From: "mal hamilton" To: References: <4E4A4134.4060007@kabelmail.de><51E78B0C619E4A90B8BBFCEDC5233A38@JimPC> Date: Tue, 16 Aug 2011 13:49:55 +0100 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2600.0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2600.0000 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="----=_NextPart_000_0013_01CC5C1B.616A98B0" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.5 required=5.0 tests=HTML_20_30,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: 0:2:477347584:93952408 X-AOL-SCOLL-URL_COUNT: 0 x-aol-sid: 3039ac1d61894e4a67c7065e X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none This is a multi-part message in MIME format. ------=_NextPart_000_0013_01CC5C1B.616A98B0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Sliding ferrite rods in and out of coils has been used since radio began = to alter inductance. You will find it in radio receiver IF transformers = as well as aluminium and brass rods. I have used this method in PA coils to adjust inductance to that = required ie a fine tune tool It does not have to be rods any shape of ferrite core will do, the same = applies to brass and other metals depending what you want to do. de=20 G3KEV ----- Original Message -----=20 From: Roger Lapthorn=20 To: rsgb_lf_group@blacksheep.org=20 Sent: Tuesday, August 16, 2011 12:57 PM Subject: Re: LF: Re: Ferrite Loops 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"? =20 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 --=20 http://g3xbm-qrp.blogspot.com/ http://www.g3xbm.co.uk http://www.youtube.com/user/g3xbm https://sites.google.com/site/sub9khz/ ------=_NextPart_000_0013_01CC5C1B.616A98B0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Sliding ferrite rods in and out of coils has = been used=20 since radio began to alter inductance. You will find it in radio = receiver IF=20 transformers as well as aluminium and brass rods.
I have used this method in PA coils to adjust = inductance=20 to that required ie a fine tune tool
It does not have to be rods any shape of ferrite = core will=20 do, the same applies to brass and other metals depending what you want = to=20 do.
de
G3KEV
 
 
----- Original Message -----
From:=20 Roger=20 Lapthorn
Sent: Tuesday, August 16, 2011 = 12:57=20 PM
Subject: Re: LF: Re: Ferrite = Loops

Hi Jim (et al)

Ferrite rods as 5-20W TX = loading=20 coils?

As long as the ferrite doesn't saturate am I right = in=20 thinking that the use of ferrite rods as coil formers for 137 and = 500kHz is=20 basically "a good idea"? 

From personal experience with = 5W this=20 worked well at 500kHz so I assume that the idea could be translated to = 136kHz=20 if using separate rods for each 500uH of inductance so the cores of = each do=20 not saturate. Am I right in thinking that if you bundle x cores = together (in=20 parallel) the core will saturate at x times the power? Making a = ferrite rod=20 based variometer would be straightforward - PVC tube with cores = sliding=20 together lengthwise for example.

Engineering large air-spaced = loading=20 coils is quite a feat whereas making up, for example, 8-10 separate = ferrite=20 coils with a range of taps on each is quite easy (and small). Less = wire would=20 be needed so the losses in the coils would be lower compared with the=20 air-spaced equivalent.

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

73s
Roger G3XBM

On 16 August 2011 11:53, James Moritz <james.moritz@btopenworld.com> wrote:
Dear=20 Tom, LF Group,

what=20 do you think about an array of many parallel mounted ferrite rods, = each of=20 them carrying only a few windigs, all windings connected in series = (and=20 then perhaps tuned) and the rods arraged in such a way that the = individual=20 apertures dont touch? Or will this lead to the dimensions of a = comparable=20 air loop ;-) ?

I am sure this would work, but = I think=20 you have also identified the limitation ;-) Fundamentally, if the = signal has=20 a particular power density at the receive site, the antenna must = intercept=20 the signal from a certain aperture area in order to deliver a = certain power=20 to the receiver. So there is a limit to how small it can practically = be,=20 although the actual shape can vary to obtain the same aperture - one = could=20 make a rough comparison between the short, wide loop vs. the long, = thin=20 ferrite rod, and a long yagi vs. a broadside array of = dipoles.

I=20 think an array of ferrite rods might be attractive in some = circumstances -=20 for instance, you could have numerous small rods stacked vertically, = to=20 produce a "ferrite rod vertical" with a small turning circle but a=20 relatively large effective area.

Cheers, Jim Moritz
73 de=20 M0BMU






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

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