From: g4gvw <g4gvw@aol.com>
To: rsgb_lf_group@blacksheep.org
In-Reply-To: <001601cc5c12$ffe69510$0401a8c0@xphd97xgq27nyf>
References: <4E4A4134.4060007@kabelmail.de>
	 <51E78B0C619E4A90B8BBFCEDC5233A38@JimPC>
	 <CAHAQVWMYed_tfH9q1So0sdCE4nQtdgu-sxybZZcpYr_2eUwNEA@mail.gmail.com>
	 <001601cc5c12$ffe69510$0401a8c0@xphd97xgq27nyf>
Date: Tue, 16 Aug 2011 16:09:42 +0100
Message-ID: <1313507382.3851.5.camel@pat-compaq-evo>
Mime-Version: 1.0
X-AOL-SCOLL-URL_COUNT: 0  
X-Spam-Score: 0.0 (/)
X-Spam-Report: autolearn=disabled,none
Subject: Re: LF: Re: Ferrite Loops
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: 7bit
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=none 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: 0:2:464589792:93952408  
X-AOL-SCOLL-URL_COUNT: 0  
x-aol-sid: 3039ac1d40594e4a888e46e6
X-AOL-IP: 195.171.43.25
X-AOL-SPF: domain : blacksheep.org SPF : none


Mal is spot on with that one. A well-known Chelmsford firm used the
technique in some of their tx units.

73


On Tue, 2011-08-16 at 13:49 +0100, mal hamilton wrote:
> 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 
> G3KEV
>  
>  
>         ----- Original Message ----- 
>         From: Roger Lapthorn 
>         To: rsgb_lf_group@blacksheep.org 
>         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"?  
>         
>         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
>         <james.moritz@btopenworld.com> 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/
>         

-- 
73 es gd dx de pat g4gvw
 qth nr felixstowe uk
(east coast, county of suffolk)