Message-ID: <000d01cc5cc3$43001a00$0401a8c0@xphd97xgq27nyf>
From: "mal hamilton" <g3kevmal@talktalk.net>
To: <rsgb_lf_group@blacksheep.org>
References: <005f01cc5c32$66a39ae0$0401a8c0@xphd97xgq27nyf> <182D3176BF9144939EF13D0CBAC4921F@JimPC>
Date: Wed, 17 Aug 2011 10:51:39 +0100
MIME-Version: 1.0
Subject: LF: Re: Re: ferrite coil
Content-Type: text/plain;
	charset="iso-8859-1"
Content-Transfer-Encoding: 7bit
Sender: owner-rsgb_lf_group@blacksheep.org
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org
X-AOL-SCOLL-URL_COUNT: 0  
x-aol-sid: 3039ac1dc1464e4b90b91662
X-AOL-IP: 195.171.43.25
X-AOL-SPF: domain : blacksheep.org SPF : none


Jim

The Collins equipment used this method in their VFO'S, permeability tuning
also ferrite slug tuned IF transformers have been around for a long time.
There seems to be some confusion about Variometer. A Variometer consists of
two coils in series with one rotated within the other to vary Inductance
whereas a ferrite moveable rod inserted inside a coil is referred to as Slug
Tuning.
 mal/g3kev

----- Original Message -----
From: "James Moritz" <james.moritz@btopenworld.com>
To: <rsgb_lf_group@blacksheep.org>
Sent: Tuesday, August 16, 2011 7:17 PM
Subject: LF: Re: ferrite coil


> Dear Mal, LF Group,
>
> >Instead of winding a tight coil on to a ferrite rod to get 270 uH and
> >tuning with a 250 p variable capacitor...
>
> The required tuning capacitance would be about 5000pF.
>
> >...instead wind an air core coil and move the ferrite rod into/out of
coil
> >for the required inductance necessary for frequency >of interest. This
> >would further reduce losses.
>
> You could tune inductance downwards in this way, but unfortunately any
> reduction would be accompanied by reduced magnetic flux due to the
received
> signal in the antenna winding. So the signal amplitude would be reduced.
> Also, I doubt if losses actually would be lower - certainly, the coil
> without the ferrite rod will have a much lower Q than with the rod in
place,
> so a point must come as the rod is withdrawn where Q decreases rapidly.
>
> Cheers, Jim Moritz
> 73 de M0BMU
>
>
>
>