Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-db01.r1000.mx.aol.com (Internet Inbound) with ESMTP id BFEC638000087; Sat, 25 Jun 2011 09:50:18 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1QaTE7-0005tM-RT for rs_out_1@blacksheep.org; Sat, 25 Jun 2011 14:48:47 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1QaTE7-0005tD-7E for rsgb_lf_group@blacksheep.org; Sat, 25 Jun 2011 14:48:47 +0100 Received: from relay.uni-heidelberg.de ([129.206.100.212]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1QaTE5-0002zI-QU for rsgb_lf_group@blacksheep.org; Sat, 25 Jun 2011 14:48:47 +0100 Received: from freitag.iup.uni-heidelberg.de (freitag.iup.uni-heidelberg.de [129.206.29.204]) by relay.uni-heidelberg.de (8.14.1/8.14.1) with ESMTP id p5PDmfDS030446 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO) for ; Sat, 25 Jun 2011 15:48:41 +0200 Received: from [129.206.22.206] (pc206.iup.uni-heidelberg.de [129.206.22.206]) by freitag.iup.uni-heidelberg.de (8.12.11.20060308/8.11.2) with ESMTP id p5PDmO1k024899 for ; Sat, 25 Jun 2011 15:48:24 +0200 Message-ID: <4E05E69B.2060803@iup.uni-heidelberg.de> Date: Sat, 25 Jun 2011 15:46:03 +0200 From: =?ISO-8859-15?Q?Stefan_Sch=E4fer?= User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; de; rv:1.9.1.8) Gecko/20100227 Thunderbird/3.0.3 MIME-Version: 1.0 To: rsgb_lf_group@blacksheep.org References: <4DF8A827.9070106@iup.uni-heidelberg.de> <01a101cc2c6a$8c31a100$1502a8c0@Clemens04> <4DFA78BC.1020106@iup.uni-heidelberg.de> <4DFB5AEB.70607@legal-medicine.de> In-Reply-To: <4DFB5AEB.70607@legal-medicine.de> X-Spam-Score: 1.4 (+) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001,RATWARE_GECKO_BUILD=1.426 Subject: Re: LF: Re: LF RX loop Content-Type: multipart/alternative; boundary="------------070808030006080203060001" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.0 required=5.0 tests=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: 0:2:444291840:93952408 X-AOL-SCOLL-URL_COUNT: 0 x-aol-sid: 3039ac1d40554e05e79a2af9 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none This is a multi-part message in MIME format. --------------070808030006080203060001 Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit Hello Peter, Clemens, Jim, LF, Before a few days i have bought a new copper tube with 18mm diameter and 1mm thickness. I formed a loop with 1m diameter. This time i put 2 copper plates into the tube and hammered it at this point where it was fixed later on a non conducting material block. Then i directly soldered the caps on this plate which was quite easy done with a big soldering iron. I need slightly more C, somewhat above 500 nF. Actually the caps are the same types, so the problem must (mainly) have been the short wires between copper tube and caps in the last version. A photo is here: http://dl.dropbox.com/u/19882028/LF/LF%20RX%20Loop.JPG This time i'm achieving a* Q of 176* in a first attempt although i want to use even more suitable caps later. In this measurement the center frequency was 137.72 kHz, the 3 dB points are at 137.31 and 138.09 kHz which sounds very good to me. Later i want to add a switch with some additional caps to make QSY to the CW region on LF which should be no problem This design is really robost and thus most suitable for a /p rig! It even works indoors , in contrast to the E field antenna. As Jim i found no better NPN Transistors like the ZTX690B for this loop preamp and they are available at RS so i will exactly build this amp and am very optimistic about the results! One more question: Does it make sense (regarding good SNR) to further try to improve the Q or does it just make frequency adjustment complicated? If the dynamic range of my soundcard can handle the signal of DCF39 and DCF49 and DLF and i should have no problem, right? The background noise should be limited by the band noise only of course. Is there a straight dependency of gain and Q? Thanks for further opinions and advice. 73, Stefan/DK7FC Am 17.06.2011 15:47, schrieb pws: > Hi Stefan, > > You wrote: > >> ... >> I found the Q of the >> loop is just 8! Is this normal? Which Q do others achieve, with a >> similar antenna for 137 kHz? >> ... >> > Confirming your findings. In the late 90th I built a 2m-loop from 1" > coax ("Flexwell") for nulling out Loran-C splatter. I remember a > bandwidth of ~12-15 kHz => Q ~= 10 with 8.2uH/165nF. > http://www.qsl.net/df3lp/projects/lfloop/index.html > > >> ... >> It is fascinating to null out s signal, which i have done the first >> time now. I can reduce the signal of DCF39 by 25 dB by turning the >> loop... >> > That's somewhat different to what could be found here. I observed very > sharp Nulls well>40dB below main lobes. May be due do the orthodox > "screened" design including the usual gap. But as you suggested that's only > true for pure groundwave reception. At VLF I'm observing the deepest null > of DHO38 (~200km; noon) at ~30deg. of elevation. > > Good luck for tomorrow, > Peter, df3lp > --------------070808030006080203060001 Content-Type: text/html; charset=ISO-8859-15 Content-Transfer-Encoding: quoted-printable X-MIME-Autoconverted: from 8bit to quoted-printable by relay.uni-heidelberg.de id p5PDmfDS030446 Hello Peter, Clemens, Jim, LF,

Before a few days i have bought a new copper tube with 18mm diameter and 1mm thickness. I formed a loop with 1m diameter. This time i put 2 copper plates into the tube and hammered it at this point where it was fixed later on a non conducting material block. Then i directly soldered the caps on this plate which was quite easy done with a big soldering iron. I need slightly more C, somewhat above 500 nF. Actually the caps are the same types, so the problem must (mainly) have been the short wires between copper tube and caps in the last version.
A photo is here: http://dl.dropbox.com/u/198820= 28/LF/LF%20RX%20Loop.JPG
This time i'm achieving a Q of 176 in a first attempt although i want to use even more suitable caps later. In this measurement the center frequency was 137.72 kHz, the 3 dB points are at 137.31 and 138.09 kHz which sounds very good to me. Later i want to add a switch with some additional caps to make QSY to the CW region on LF which should be no problem
This design is really robost and thus most suitable for a /p rig! It even works indoors , in contrast to the E field antenna.
As Jim i found no better NPN Transistors=A0 like the ZTX690B for this loop preamp and they are available at RS so i will exactly build this amp and am very optimistic about the results!

One more question: Does it make sense (regarding good SNR) to further try to improve the Q or does it just make frequency adjustment complicated? If the dynamic range of my soundcard can handle the signal of DCF39 and DCF49 and DLF and i should have no problem, right? The background noise should be limited by the band noise only of course. Is there a straight dependency of gain and Q?

Thanks for further opinions and advice.

73, Stefan/DK7FC


Am 17.06.2011 15:47, schrieb pws:
Hi Stefan,

You wrote:
  
...
I found the Q of the
loop is just 8! Is this normal? Which Q do others achieve, with a
similar antenna for 137 kHz?
...
    
Confirming your findings. In the late 90th I built a 2m-loop from 1"
coax ("Flexwell") for nulling out Loran-C splatter. I remember a
bandwidth of ~12-15 kHz =3D> Q ~=3D 10 with 8.2uH/165nF.
http://www.qsl.net/df3lp/projects/lfloop/index.htm=
l

  
...
It is fascinating to null out s signal, which i have done the first
time now. I can reduce the signal of DCF39 by 25 dB by turning the
loop...
    
That's somewhat different to what could be found here. I observed very
sharp Nulls well >40dB below main lobes. May be due do the orthodox
"screened" design including the usual gap. But as you suggested that's on=
ly
true for pure groundwave reception. At VLF I'm observing the deepest null
of DHO38 (~200km; noon) at ~30deg. of elevation.

Good luck for tomorrow,
Peter, df3lp
  
--------------070808030006080203060001--