Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-dc02.r1000.mx.aol.com (Internet Inbound) with ESMTP id 3BDA8380000CF; Tue, 16 Aug 2011 16:18:25 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1QtQ55-0005rD-CH for rs_out_1@blacksheep.org; Tue, 16 Aug 2011 21:17:47 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1QtQ54-0005r4-Ox for rsgb_lf_group@blacksheep.org; Tue, 16 Aug 2011 21:17:46 +0100 Received: from rhcavuit02.kulnet.kuleuven.be ([134.58.240.130] helo=cavuit02.kulnet.kuleuven.be) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1QtQ52-0004z8-7n for rsgb_lf_group@blacksheep.org; Tue, 16 Aug 2011 21:17:46 +0100 X-KULeuven-Envelope-From: rik.strobbe@fys.kuleuven.be X-KULeuven-Scanned: Found to be clean X-KULeuven-ID: 3F728128081.A6DA1 X-KULeuven-Information: Katholieke Universiteit Leuven Received: from smtps01.kuleuven.be (smtpshost01.kulnet.kuleuven.be [134.58.240.74]) by cavuit02.kulnet.kuleuven.be (Postfix) with ESMTP id 3F728128081 for ; Tue, 16 Aug 2011 22:17:37 +0200 (CEST) Received: from ICTS-S-HUB-N4.luna.kuleuven.be (icts-s-hub-n4.luna.kuleuven.be [10.112.9.14]) by smtps01.kuleuven.be (Postfix) with ESMTP id F026E31E702 for ; Tue, 16 Aug 2011 22:17:36 +0200 (CEST) Received: from ICTS-S-EXC2-CA.luna.kuleuven.be ([10.112.11.13]) by ICTS-S-HUB-N4.luna.kuleuven.be ([10.112.9.14]) with mapi; Tue, 16 Aug 2011 22:17:36 +0200 X-Kuleuven: This mail passed the K.U.Leuven mailcluster From: Rik Strobbe To: "rsgb_lf_group@blacksheep.org" Date: Tue, 16 Aug 2011 22:17:36 +0200 Thread-Topic: LF: Re: Ferrite Loops Thread-Index: AcxcDClYqnVP7UrwRoCM+oUnbgaybQAQzkQh Message-ID: References: <4E4A4134.4060007@kabelmail.de> <51E78B0C619E4A90B8BBFCEDC5233A38@JimPC>, In-Reply-To: Accept-Language: nl-NL, nl-BE Content-Language: nl-BE X-MS-Has-Attach: X-MS-TNEF-Correlator: acceptlanguage: nl-NL, nl-BE MIME-Version: 1.0 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="_000_BF4A524700075746A6467658DFC7102CB0B27CF220ICTSSEXC2CAlu_" 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, 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: 0:2:433547200:93952408 X-AOL-SCOLL-URL_COUNT: 0 x-aol-sid: 3039ac1d40824e4ad091164b X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none --_000_BF4A524700075746A6467658DFC7102CB0B27CF220ICTSSEXC2CAlu_ Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Hello Roger, in the early days of 136kHz I did use a "ferrite rod variometer" for fine t= uning the antenna. It was a 700uH coil (abt. 100 winding of 1mm CuL on a 10cm diameter former = if I remind well), with a ferritte rod that could be inserted at the center= of the coil. Inserting the rod completely increased the inductance to abt.= 1mH. I did test my complete supply of ferrite rods (abt. 50) and with almost all= of them inserting the rod caused a nefast loss and the rods got very hot w= ith 100W RF. But a couple of rods got only lukewarm and the losses were neg= lectable compared to ground loss. Interesting was that these low loss rods also introduced the smallest varia= tion of L (abt. 50% increase) while with some of the lossy rods I could inc= rease the L up to 2.5mH. I did use this variometer for a while and it worked fine, but after increas= ing power to 450W even the low loww rods got too hot and I had to use a tra= ditional variometer. 73, Rik ON7YD ________________________________ Van: owner-rsgb_lf_group@blacksheep.org [owner-rsgb_lf_group@blacksheep.org= ] namens Roger Lapthorn [rogerlapthorn@gmail.com] Verzonden: dinsdag 16 augustus 2011 13:57 Aan: rsgb_lf_group@blacksheep.org Onderwerp: 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 id= ea"? >From personal experience with 5W this worked well at 500kHz so I assume tha= t the idea could be translated to 136kHz if using separate rods for each 50= 0uH of inductance so the cores of each do not saturate. Am I right in think= ing that if you bundle x cores together (in parallel) the core will saturat= e at x times the power? Making a ferrite rod based variometer would be stra= ightforward - PVC tube with cores sliding together lengthwise for example. Engineering large air-spaced loading coils is quite a feat whereas making u= p, 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 coi= ls 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, 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 relativel= y 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/ --_000_BF4A524700075746A6467658DFC7102CB0B27CF220ICTSSEXC2CAlu_ Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Hello Roger,
 
in the early days of 136kHz I did use= a "ferrite rod variometer" for fine tuning the antenna.
It was a 700uH coil (abt. 100 winding= of 1mm CuL on a 10cm diameter former if I remind well), with a ferrit= te rod that could be inserted at the center of the coil. Inserting the rod = completely increased the inductance to abt. 1mH.
I did test my complete supply of ferr= ite rods (abt. 50) and with almost all of them inserting the rod caused a n= efast loss and the rods got very hot with 100W RF. But a couple of rod= s got only lukewarm and the losses were neglectable compared to ground loss.
Interesting was that these low loss r= ods also introduced the smallest variation of L (abt. 50% increase) while w= ith some of the lossy rods I could increase the L up to 2.5mH.
 
I did use this variometer for a while= and it worked fine, but after increasing power to 450W even the low loww r= ods got too hot and I had to use a traditional variometer.
 
73, Rik  ON7YD
 
=  
Van: owner-rsgb_l= f_group@blacksheep.org [owner-rsgb_lf_group@blacksheep.org] namens Roger La= pthorn [rogerlapthorn@gmail.com]
Verzonden: dinsdag 16 augustus 2011 13:57
Aan: rsgb_lf_group@blacksheep.org
Onderwerp: 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 go= od idea"? 

>From personal experience with 5W this worked well at 500kHz so I assume tha= t the idea could be translated to 136kHz if using separate rods for each 50= 0uH of inductance so the cores of each do not saturate. Am I right in think= ing that if you bundle x cores together (in parallel) the core will saturate at x times the power? Making a ferrit= e rod based variometer would be straightforward - PVC tube with cores slidi= ng together lengthwise for example.

Engineering large air-spaced loading coils is quite a feat whereas making u= p, 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 coi= ls 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 <james.moritz@b= topenworld.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 limit to how small it can practically= be, although the actual shape can vary to obtain the same aperture - one c= ould make a rough comparison between the short, wide loop vs. the long, thi= n 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 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-q= rp.blogspot.com/
http://www.g3xbm.co.uk=
http://www.= youtube.com/user/g3xbm
https:= //sites.google.com/site/sub9khz/

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