From: pat gillen <g4gvw@aol.com>
To: rsgb_lf_group@blacksheep.org
In-Reply-To: <31E46023A2704DF8A4431C0B44BAE495@Hugh>
References: <001101ca621e$dcdc3380$96949a80$@princeton.edu>
	 <20091110192309.4v8agotbs0k0gocs@webmail6.kuleuven.be>
	 <004a01ca6249$d91531e0$8b3f95a0$@princeton.edu>
	 <20091110222951.cr4qtrqagcwcowok@webmail6.kuleuven.be>
	 <4AFAAE9C.1070304@ukonline.co.uk>  <31E46023A2704DF8A4431C0B44BAE495@Hugh>
Date: Wed, 11 Nov 2009 13:25:36 +0000
Message-Id: <1257945936.10404.7.camel@pat-desktop-dell>
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Subject: Re: LF: Re: Ferrite characteristics
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Hi Peter,
I tend to do something similar to Hugh but perhaps a little less
"scientifically" viz.; When playing toroids etc. I determine which ones
are successful for a particular application and use an LCR meter to
measure the inductance of 5 turns of approx 14g copper and mark the
toroid accordingly. My little stock is marked in this way and a note is
made of the apps for which they were suitable (or in some cases
unsuitable). I am sure there are much better ways but it gets me by.

73 de Pat g4gvw


On Wed, 2009-11-11 at 12:55 +0000, Hugh_m0wye wrote:
> Hi Peter,
> In the past I have wound a few turns aound the core and measured the 
> Inductance. From this you can calculate the AL value, or "Inductance Factor" 
> in nH per turns squared. I measured the Inductance on an LCR meter, but you 
> could resonate the coil against a capacitor and use a GDO as you suggest.
> 
> Number of turns  = square root of (L / AL) where L is inductance in nH.
> 
> From this you can compare to published figures, for example the RM series of 
> Ferrite cores (RS used to publish tables which included the AL value, in 
> their catalogues)
> 
> 73
> Hugh M0WYE
> 
> 
> ----- Original Message ----- 
> From: "Peter Dodd" <g3ldo@ukonline.co.uk>
> To: <rsgb_lf_group@blacksheep.org>
> Sent: Wednesday, November 11, 2009 12:31 PM
> Subject: LF: Ferrite characteristics
> 
> 
> > Does anyone know of a method of measuring the characteristics 
> > (permeability) of ferrite cores?  I have a box of these most without any 
> > identification although I do have T200, 68-2T and T68-2s whose 
> > characteristics are known.
> >
> > It occurs to me that you can make a tuned circuit and measure resonance 
> > with a GDO when a ferrite core is inserted into the inductance. A graph 
> > could be made of the different resonances with different cores, to 
> > extrapolate the unknowns.
> >
> > However I think that ferrite bulk might be a problem. For example I guess 
> > the red T cores use the same material but would there be a difference 
> > between the T200 and the T68?
> >
> > I have lots of material about ferrites in general - I just want to know 
> > what I have in my junk box. I am not interested in exact measurements, I 
> > just want to know if a core is suitable for a specific job.
> >
> > Regards
> >
> > Peter, G3LDO
> >
> > 
> 
>