Return-Path: Received: from mtain-dc01.r1000.mx.aol.com (mtain-dc01.r1000.mx.aol.com [172.29.64.129]) by air-me09.mail.aol.com (v129.4) with ESMTP id MAILINME094-8bc34d44a629188; Sat, 29 Jan 2011 18:43:37 -0500 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-dc01.r1000.mx.aol.com (Internet Inbound) with ESMTP id 52434380000AE; Sat, 29 Jan 2011 18:43:35 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1PjKRT-0007mv-10 for rs_out_1@blacksheep.org; Sat, 29 Jan 2011 23:42:55 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1PjKRS-0007mm-Hm for rsgb_lf_group@blacksheep.org; Sat, 29 Jan 2011 23:42:54 +0000 Received: from imr-db01.mx.aol.com ([205.188.91.95]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1PjKRQ-0003Wb-Lj for rsgb_lf_group@blacksheep.org; Sat, 29 Jan 2011 23:42:54 +0000 Received: from mtaout-mb06.r1000.mx.aol.com (mtaout-mb06.r1000.mx.aol.com [172.29.41.70]) by imr-db01.mx.aol.com (8.14.1/8.14.1) with ESMTP id p0TNglC1029531 for ; Sat, 29 Jan 2011 18:42:47 -0500 Received: from White (nrbg-4d07553e.pool.mediaWays.net [77.7.85.62]) by mtaout-mb06.r1000.mx.aol.com (MUA/Third Party Client Interface) with ESMTPA id 5EE74E0000F7 for ; Sat, 29 Jan 2011 18:42:41 -0500 (EST) Message-ID: From: "Markus Vester" To: References: <4D449E50.2020507@o2.co.uk> Date: Sun, 30 Jan 2011 00:42:40 +0100 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal Importance: Normal X-Mailer: Microsoft Windows Live Mail 12.0.1606 X-MimeOLE: Produced By Microsoft MimeOLE V12.0.1606 X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: Re: LF: LF coil tuning Content-Type: multipart/alternative; boundary="----=_NextPart_000_0033_01CBC016.999D2FA0" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.9 required=5.0 tests=HTML_30_40,HTML_MESSAGE, MISSING_OUTLOOK_NAME 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-sid: 3039ac1d40814d44a62755fd X-AOL-IP: 195.171.43.25 ------=_NextPart_000_0033_01CBC016.999D2FA0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Yes it works well, also VLF. The nice thing is that you don't need the= flexible connections for the rotating part, wheras the downsides may= be less tuning range (only "up" in frequency), and a slight increase= of losses. The wire loop can be replaced by a metal plate, but (at le= ast for LF), a shorted multiturn coil made from RF litz would minimize= induced losses. For 9 kHz I have considered rotating a ferrite plate, sandwitched betw= een two copper sheets. In an orientation parallel to the magnetic fiel= d, the ferrite enhances inductance, whereas in the orthogonal position= the eddy currents decrease it. In my case I ended up without the copp= er as I got sufficient tuning range with the ferrite alone. The 90=B0= turning range (compared to 180=B0 for a traditional variometer) feels= a bit unusual, but allows simple mechanical operation by pulling a st= ring attached to one side of the plate. Best 73, Markus (DF6NM) From: Peter Dodd=20 Sent: Sunday, January 30, 2011 12:10 AM To: rsgb_lf_group@blacksheep.org=20 Subject: LF: LF coil tuning The traditional method of tuning an LF loading coil is to use a variom= eter. I have been investigating methods of tuning coils for mobile use and= one=20 method that appeared briefly in one of the ARRL Handbooks of the 50s= =20 was the shorted turn method of tuning. I tried a home made coil of 136uH on a 5cm diameter former and using= a=20 shorted turn of 2mm insulated wire and obtained a tuning range of 32uH= .=20 (136 - 102uH). Has anyone out there tried this? Regards Peter G3LDO =20 ------=_NextPart_000_0033_01CBC016.999D2FA0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Yes it works well, also VLF. The= nice thing is=20 that you don't need the flexible connections for the rotating part, wh= eras the=20 downsides may be less tuning range (only "up" in frequency), and a sli= ght=20 increase of losses. The wire loop can be replaced by a metal plate, bu= t (at=20 least for LF), a shorted multiturn coil made from RF litz wo= uld=20 minimize induced losses.
 
For 9 kHz I have considered rota= ting=20 a ferrite plate, sandwitched between two copper sheets. = ;In an=20 orientation parallel to the magnetic field, the ferrite= enhances=20 inductance, whereas in the orthogonal position the eddy currents= decrease=20 it. In my case I ended up without the copper as I got= sufficient=20 tuning range with the ferrite alone. The= 90=B0 turning=20 range (compared to 180=B0 for a traditional variometer) feels a bit un= usual, but=20 allows simple mechanical operation by pulling a string attached to one= side of=20 the plate.
 
Best 73,
Markus (DF6NM)

From: Peter Dodd
Sent: Sunday, January 30, 2011 12:10 AM
Subject: LF: LF coil tuning

The=20 traditional method of tuning an LF loading coil is to use a variometer= .

I=20 have been investigating methods of tuning coils for mobile use and one= =20
method that appeared briefly  in one of the ARRL Handbooks of= the 50s=20
was the shorted turn method of tuning.

I tried a home made= coil of=20 136uH on a 5cm diameter former and using a
shorted turn of 2mm ins= ulated=20 wire and obtained a tuning range of 32uH.
(136 - 102uH).

Ha= s anyone=20 out there tried this?

Regards

Peter=20 G3LDO

         &nb= sp; =20



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