Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-md03.r1000.mx.aol.com (Internet Inbound) with ESMTP id 18CE9380000D7; Mon, 15 Aug 2011 12:34:14 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Qt06W-0005dy-SF for rs_out_1@blacksheep.org; Mon, 15 Aug 2011 17:33:32 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1Qt06W-0005dp-B4 for rsgb_lf_group@blacksheep.org; Mon, 15 Aug 2011 17:33:32 +0100 Received: from mout9.freenet.de ([195.4.92.99]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1Qt06V-0006g8-13 for rsgb_lf_group@blacksheep.org; Mon, 15 Aug 2011 17:33:32 +0100 Received: from [195.4.92.17] (helo=7.mx.freenet.de) by mout9.freenet.de with esmtpa (ID dl4yhf@freenet.de) (port 25) (Exim 4.76 #5) id 1Qt06U-0003N6-24 for rsgb_lf_group@blacksheep.org; Mon, 15 Aug 2011 18:33:30 +0200 Received: from blfd-4d086867.pool.mediaways.net ([77.8.104.103]:3999 helo=[192.168.0.101]) by 7.mx.freenet.de with esmtpsa (ID dl4yhf@freenet.de) (TLSv1:CAMELLIA256-SHA:256) (port 465) (Exim 4.76 #5) id 1Qt06T-0007jh-86 for rsgb_lf_group@blacksheep.org; Mon, 15 Aug 2011 18:33:29 +0200 Message-ID: <4E494A57.90105@freenet.de> Date: Mon, 15 Aug 2011 18:33:27 +0200 From: wolf_dl4yhf User-Agent: Mozilla/5.0 (Windows NT 5.1; rv:5.0) Gecko/20110624 Thunderbird/5.0 MIME-Version: 1.0 To: rsgb_lf_group@blacksheep.org References: <68BE37BD69E54DEE89CEBA8E30E9B94E@PcMinto> <4E47FFE9.10100@iup.uni-heidelberg.de> <3ED8E5422F1F45DBB8186E9D9870AD63@PcMinto> <4E480E02.9020706@iup.uni-heidelberg.de> <938BF599006244949F6CDDB5BA91F347@PcMinto> <4E482FBD.7030402@freenet.de> <4E484183.9090805@iup.uni-heidelberg.de> In-Reply-To: <4E484183.9090805@iup.uni-heidelberg.de> X-Spam-Score: 1.4 (+) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001,RATWARE_GECKO_BUILD=1.426 Subject: Re: LF: Ferrite RX antennas Content-Type: multipart/alternative; boundary="------------020500010807050003030404" 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 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: 0:2:461151520:93952408 X-AOL-SCOLL-URL_COUNT: 0 x-aol-sid: 3039ac1d60574e494a860a84 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none This is a multi-part message in MIME format. --------------020500010807050003030404 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Hi Stefan, The rods were found in Friedrichshafen for a bargain price. I later discovered (most likely after the topic had been discussed here, or in the VLF group) that these rods are used for inductive welding (google("Ferrite Impeder Rod"). Here's a bundle of them: http://www.qsl.net/dl4yhf/vlf_rdf/vlf_rdf_loop.html They are 20 cm long. The most effective use (to "catch the magnetic field from a distant transmitter") is NOT to connect them 'parallel' in a bundle, but to connect them in series (up to a certain point). This is much in contrast to the esoteric sleeve thingy seen somewhere on the web. 73, Wolf . Am 14.08.2011 23:43, schrieb Stefan Schäfer: > Wolf, > > Which dimensions has your ferrite rod had? > > Never thought i will find a source for rods that are longer than 10 cm > but see: > http://www.box73.de/catalog/product_info.php?products_id=1422&osCsid=rqlpfme957i65d7etjil1ntru5 > > even an official distributor.. > > Any better links? > > 73, Stefan/DK7FC > > Am 14.08.2011 22:27, schrieb wolf_dl4yhf: >> Ferrite RX antennas.. been there when 136 kHz started. >> Not as good as a larger air-core loop, possibly noise caused by the >> Barkhausen effect or similar effects, nonlinearities, etc. >> Also beware the ferrite is a semiconductor so you will need some >> E-field screening, otherwise the ferrite material will couple noise >> into the windings. But it's not as bad as this may sound; actually I >> used a ferrite antenna for reception for some years until I >> discovered I had to disconnect the ...errr... RF counterpoise from >> the main antenna from the mains "ground", and only use an earthstake >> during receive, at DF0WD. >> >> On the other hand, it's compact, relatively light-weight, and (in a >> resonant configuration) gives a nice preselector. >> I remember when I connected a ferrite antenna to a tiny receiver with >> SA612 "gilbert cell mixer", the first signal I heard was G3KEV >> calling cq in CW. Q5 in SSB bandwidth. >> Such a receiver is extremely handy to go /p for reception, and >> compare different sites. >> >> 73, >> Wolf DL4YHF. >> >> >> Am 14.08.2011 21:43, schrieb Minto Witteveen: >>> >>> I haven’t thought about ferrite RX antenna for LF….My guess is that >>> it is not going to work – not without an external antenna coupled to >>> the ferrite, and then what’s the point? >>> DCF77 clocks often have trouble locking indoors or in the >>> neighborhood of ‘QRM’ generators like PC’s, and look what power >>> DCF77 is using… >>> I could be entirely wrong of course… >>> >>> 73’ Minto pa3bca >>> >>> *From:* Stefan Schäfer >>> *Sent:* Sunday, August 14, 2011 20:03 >>> *To:* rsgb_lf_group@blacksheep.org >>> >>> *Subject:* Re: LF: Re: 137 grabbers >>> >>> BTW what do you think about a ferrite RX antenna for LF? Now i'm >>> opening an older discussion i expect ;-) >>> >>> 73, Stefan/DK7FC >>> >>> >> --------------020500010807050003030404 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: 8bit Hi Stefan,
The rods were found in Friedrichshafen for a bargain price. I later discovered (most likely after the topic had been discussed here, or in the VLF group) that these rods are used for inductive welding (google("Ferrite Impeder Rod"). Here's a bundle of them:

http://www.qsl.net/dl4yhf/vlf_rdf/vlf_rdf_loop.html

They are 20 cm long.

The most effective use (to "catch the magnetic field from a distant transmitter") is NOT to connect them 'parallel' in a bundle, but to connect them in series (up to a certain point). This is much in contrast to the esoteric sleeve thingy seen somewhere on the web.

73,
   Wolf .



Am 14.08.2011 23:43, schrieb Stefan Schäfer:
Wolf,

Which dimensions has your ferrite rod had?

Never thought i will find a source for rods that are longer than 10 cm but see: http://www.box73.de/catalog/product_info.php?products_id=1422&osCsid=rqlpfme957i65d7etjil1ntru5

even an official distributor..

Any better links?

73, Stefan/DK7FC

Am 14.08.2011 22:27, schrieb wolf_dl4yhf:
Ferrite RX antennas.. been there when 136 kHz started.
Not as good as a larger air-core loop, possibly noise caused by the Barkhausen effect or similar effects, nonlinearities, etc.
Also beware the ferrite is a semiconductor so you will need some E-field screening, otherwise the ferrite material will couple noise into the windings. But it's not as bad as this may sound; actually I used a ferrite antenna for reception for some years until I discovered I had to disconnect the ...errr... RF counterpoise from the main antenna from the mains "ground", and only use an earthstake during receive, at DF0WD.

On the other hand, it's compact, relatively light-weight, and (in a resonant configuration) gives a nice preselector.
I remember when I connected a ferrite antenna to a tiny receiver with SA612 "gilbert cell mixer", the first signal I heard was G3KEV calling cq in CW.  Q5 in SSB bandwidth.
Such a receiver is extremely handy to go /p for reception, and compare different sites.

73,
   Wolf DL4YHF.


Am 14.08.2011 21:43, schrieb Minto Witteveen:

I haven’t thought about ferrite RX antenna for LF….My guess is that it is not going to work – not without an external antenna coupled to the ferrite, and then what’s the point?
DCF77 clocks often have trouble locking indoors or in the neighborhood of ‘QRM’ generators like PC’s, and look what power DCF77 is using…
I could be entirely wrong of course…

73’ Minto pa3bca

 
Sent: Sunday, August 14, 2011 20:03
Subject: Re: LF: Re: 137 grabbers
 
<snip>
BTW what do you think about a ferrite RX antenna for LF? Now i'm opening an older discussion i expect ;-)

73, Stefan/DK7FC




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