Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-dk01.r1000.mx.aol.com (Internet Inbound) with ESMTP id 353B2380000E2; Wed, 28 Sep 2011 16:48:14 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1R911g-00018X-Iu for rs_out_1@blacksheep.org; Wed, 28 Sep 2011 21:46:44 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1R911f-00018O-FV for rsgb_lf_group@blacksheep.org; Wed, 28 Sep 2011 21:46:43 +0100 Received: from mout3.freenet.de ([195.4.92.93]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1R911d-0007c6-Tk for rsgb_lf_group@blacksheep.org; Wed, 28 Sep 2011 21:46:43 +0100 Received: from [195.4.92.19] (helo=9.mx.freenet.de) by mout3.freenet.de with esmtpa (ID dl4yhf@freenet.de) (port 25) (Exim 4.76 #5) id 1R911b-00082V-Ts for rsgb_lf_group@blacksheep.org; Wed, 28 Sep 2011 22:46:39 +0200 Received: from blfd-5d822a03.pool.mediaways.net ([93.130.42.3]:1695 helo=[192.168.178.21]) by 9.mx.freenet.de with esmtpsa (ID dl4yhf@freenet.de) (TLSv1:CAMELLIA256-SHA:256) (port 465) (Exim 4.76 #1) id 1R911b-0000t5-8H for rsgb_lf_group@blacksheep.org; Wed, 28 Sep 2011 22:46:39 +0200 Message-ID: <4E8387AD.2050508@freenet.de> Date: Wed, 28 Sep 2011 22:46:37 +0200 From: wolf_dl4yhf User-Agent: Mozilla/5.0 (Windows NT 5.1; rv:6.0.2) Gecko/20110902 Thunderbird/6.0.2 MIME-Version: 1.0 To: rsgb_lf_group@blacksheep.org References: <16BC8B3CA8672445BC2A29B4C14A26D4379ED2AAB4@exlnmb01.eur.nsroot.net> <4DF9EFD1.5010208@iup.uni-heidelberg.de> <1313780109.51443.YahooMailNeo@web111907.mail.gq1.yahoo.com> <9CD1E11E8BC9402CB4AECECAC4088443@JimPC> <1314394178.5030.YahooMailNeo@web111905.mail.gq1.yahoo.com> <1314641183.5605.YahooMailNeo@web111910.mail.gq1.yahoo.com> <4E5CBC9A.5020900@iup.uni-heidelberg.de> <1314705226.37125.YahooMailNeo@web111901.mail.gq1.yahoo.com> <4E5CF192.3040905@legal-medicine.de> <1317076720.22768.YahooMailNeo@web29509.mail.ird.yahoo.com> <1317077173.13177.YahooMailNeo@web29509.mail.ird.yahoo.com> <1317119515.35504.YahooMailNeo@web29502.mail.ird.yahoo.com> <1317119586.50531.YahooMailNeo@web29505.mail.ird.yahoo.com> <4E81B80E.3030201@iup.uni-heidelberg.de> <1317136545.77621.YahooMailNeo@web29513.mail.ird.yahoo.com> <4E823542.90102@iup.uni-heidelberg.de> <1317236702.88673.YahooMailNeo@web29511.mail.ird.yahoo.com> In-Reply-To: <1317236702.88673.YahooMailNeo@web29511.mail.ird.yahoo.com> X-Spam-Score: 1.4 (+) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001,RATWARE_GECKO_BUILD=1.426 Subject: Re: LF: Re: My first ferrite experiments Content-Type: multipart/alternative; boundary="------------070406030903010505080209" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: ** X-Spam-Status: No, hits=2.0 required=5.0 tests=HTML_30_40,HTML_MESSAGE, NO_EXPERIENCE 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: 0:2:457058848:93952408 X-AOL-SCOLL-URL_COUNT: 0 x-aol-sid: 3039ac1db4054e83880d7b7e X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none This is a multi-part message in MIME format. --------------070406030903010505080209 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 8bit Hi Daniele, Looking at those alligator clips: Did you ever remove the rubber insulation, and check the connection between clip and cable, and check the 'copper diameter' of these cables ? I did, and found that... a) they didn't even solder them, but used a trashy loose "crimp" (well, not really crimped but crippled) connection, the copper conductor folded back over the wire's insulation, sometimes only slightly touching the chrome surface of the clip, b) there's a ridiculously low amount of copper in those wire ! (lot of PVC which makes you *think* the wire is thick, but it's crap) Cure: Replaced the wire with other colourful cabling salvaged from a PC power supply, and SOLDERED the wire to the clips. Effect: DC resistance "from clip to clip" droppe to less than 25 % of the original, for the same cable length. Maybe, if those cables are part of your parallel resonant circuit on the test bench, they are a show stopper - besides the close aluminium shield, which should really be a bit closer away from the rod / coil, or be slotted, as already suggested by Peter. Cheers, Wolf . Am 28.09.2011 21:05, schrieb Daniele Tincani: > Hello Stefan, > this morning I received the litz wire and tried another build, using a > 16 mm PVC tube to enclose the 3 x ferrite rods. I wound 70 turns of > litz (as good as I could) and went to the test bench again to measure > Q (please see the attached picture). In fact, things have improved a > bit. With the air varcap I'm using for these tests, tuning can range > from about 235 KHz up to about 978 KHz. Using nominal min/max valued > of capacitor, this gives approx L = 670uH which is very good for my > purposes. > Unfortunately Q - although improved - is still quite low: about 104 @ > 235 KHz, about 60 @ 978 KHz. > As I don't plan to try another build of the ferrite-cored coil, I can > only hope that Q will improve further with shorter and better > connections with the capacitor. > Many thanks to you, Stefan, for the very helpful suggestions! > Best regards > Daniele > > *Da:* Stefan Schäfer > *A:* rsgb_lf_group@blacksheep.org > *Inviato:* Martedì 27 Settembre 2011 22:42 > *Oggetto:* Re: LF: Re: My first ferrite experiments > > Hi Daniele, > > Am 27.09.2011 17:15, schrieb Daniele Tincani: >> Hello Stefan, >> > but maybe the Q is reduced by the aluminium shield! >> Do you think the aluminium could be the problem or the distance >> between the coil and the core? > The wire shouldn't wound directly on the rod. I have a PVC tube above > the rod and so the wire is in a distance of about 3 mm to the rod. I > used litz wire and got a Q of 485... > >> I could replace the aluminium tube with a plastic tube, if shielding >> is not necessary, but this would not improve the Q if the problem is >> the gap between the coil and the core. > Just experiment what is the best solution. But the aluminium shield - > if used - should be thin and can be applied above the winding in some > distance. I know you have much QRM at home so probably an E field > shield makes sense here. Anyway you will be bothered by the local > magnetic QRM of course. > I personally think that a shield is not necessary if you are /p and > far away from man made noise. Then, a higher Q helps more than the > shield and a Q of 30! > >> > Are the rods galvanically separated from each other by a thin >> plastic tape? What type is the ferrite material? >> Yes I put two layers of plastic tape on tips of each rod. The ferrite >> material is russian MU400HH. > Fine! I also use the same ferrite type and 55 turns. Your cap is > surely the best what you can use. So shorten the wires between L and C > and measure the Q on 137 kHz. If it is still in the range of 30, i > assume the shield causes high losses. > Another idea: There is some conducting spray available. Maybe this can > help here? No experience with that, just a spontaneous idea... > http://it.farnell.com/_/kontakt-chemie-emv-35-200ml/rivestimento-conductive-emv-35/dp/220115 > > > > > 73, Stefan/DK7FC > > --------------070406030903010505080209 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Hi Daniele,

Looking at those alligator clips: Did you ever remove the rubber insulation, and check the connection between clip and cable, and check the 'copper diameter' of these cables ?
I did, and found that...

a) they didn't even solder them, but used a trashy loose "crimp" (well, not really crimped but crippled) connection, the copper conductor folded back over the wire's insulation, sometimes only slightly touching the chrome surface of the clip,

b) there's a ridiculously low amount of copper in those wire !  (lot of PVC which makes you *think* the wire is thick, but it's crap)

Cure: Replaced the wire with other colourful cabling salvaged from a PC power supply, and SOLDERED the wire to the clips.

Effect: DC resistance "from clip to clip" droppe to less than 25 % of the original, for the same cable length.

Maybe, if those cables are part of your parallel resonant circuit on the test bench, they are a show stopper - besides the close aluminium shield, which should really be a bit closer away from the rod / coil, or be slotted, as already suggested by Peter.

Cheers,
   Wolf .

Am 28.09.2011 21:05, schrieb Daniele Tincani:
Hello Stefan,
 
this morning I received the litz wire and tried another build, using a 16 mm PVC tube to enclose the 3 x ferrite rods. I wound 70 turns of litz (as good as I could) and went to the test bench again to measure Q (please see the attached picture). In fact, things have improved a bit. With the air varcap I'm using for these tests, tuning can range from about 235 KHz up to about 978 KHz. Using nominal min/max valued of capacitor, this gives approx L = 670uH which is very good for my purposes.
Unfortunately Q - although improved - is still quite low: about 104 @ 235 KHz, about 60 @ 978 KHz.
As I don't plan to try another build of the ferrite-cored coil, I can only hope that Q will improve further with shorter and better connections with the capacitor.
Many thanks to you, Stefan, for the very helpful suggestions!
 
Best regards
Daniele
 

Da: Stefan Schäfer <Stefan.Schaefer@iup.uni-heidelberg.de>
A: rsgb_lf_group@blacksheep.org
Inviato: Martedì 27 Settembre 2011 22:42
Oggetto: Re: LF: Re: My first ferrite experiments

Hi Daniele,

Am 27.09.2011 17:15, schrieb Daniele Tincani:
Hello Stefan,
 
> but maybe the Q is reduced by the aluminium shield!
Do you think the aluminium could be the problem or the distance between the coil and the core?
The wire shouldn't wound directly on the rod. I have a PVC tube above the rod and so the wire is in a distance of about 3 mm to the rod. I used litz wire and got a Q of 485...

I could replace the aluminium tube with a plastic tube, if shielding is not necessary, but this would not improve the Q if the problem is the gap between the coil and the core.
Just experiment what is the best solution. But the aluminium shield - if used - should be thin and can be applied above the winding in some distance. I know you have much QRM at home so probably an E field shield makes sense here. Anyway you will be bothered by the local magnetic QRM of course.
I personally think that a shield is not necessary if you are /p and far away from man made noise. Then, a higher Q helps more than the shield and a Q of 30!

 
> Are the rods galvanically separated from each other by a thin plastic tape? What type is the ferrite material?
Yes I put two layers of plastic tape on tips of each rod. The ferrite material is russian MU400HH.
Fine! I also use the same ferrite type and 55 turns. Your cap is surely the best what you can use. So shorten the wires between L and C and measure the Q on 137 kHz. If it is still in the range of 30, i assume the shield causes high losses.
Another idea: There is some conducting spray available. Maybe this can help here? No experience with that, just a spontaneous idea...
http://it.farnell.com/_/kontakt-chemie-emv-35-200ml/rivestimento-conductive-emv-35/dp/220115



73, Stefan/DK7FC



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