Return-Path: Received: from rly-de02.mx.aol.com (rly-de02.mail.aol.com [172.19.170.138]) by air-de05.mail.aol.com (v126.13) with ESMTP id MAILINDE051-4b94b29105d2b4; Wed, 16 Dec 2009 11:53:00 -0500 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by rly-de02.mx.aol.com (v125.7) with ESMTP id MAILRELAYINDE024-4b94b29105d2b4; Wed, 16 Dec 2009 11:52:47 -0500 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1NKx3W-0006LV-9C for rs_out_1@blacksheep.org; Wed, 16 Dec 2009 16:48:54 +0000 Received: from [83.244.159.144] (helo=relay3.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1NKx3V-0006LM-Ek for rsgb_lf_group@blacksheep.org; Wed, 16 Dec 2009 16:48:53 +0000 Received: from lnx500.hrz.tu-darmstadt.de ([130.83.156.225]) by relay3.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1NKx5o-00051U-HW for rsgb_lf_group@blacksheep.org; Wed, 16 Dec 2009 16:51:18 +0000 Received: from FILE-SERVER-HST.hst.e-technik.tu-darmstadt.de (File-Server-HST.hst.e-technik.tu-darmstadt.de [130.83.212.129]) by lnx500.hrz.tu-darmstadt.de (8.14.2/8.14.2/HRZ/PMX) with SMTP id nBGGjdUS017659 for ; Wed, 16 Dec 2009 17:45:40 +0100 (envelope-from schaefer@hst.tu-darmstadt.de) Received: from [127.0.0.1] (helo=File-Server-HST.hst.e-technik.tu-darmstadt.de) by FILE-SERVER-HST.hst.e-technik.tu-darmstadt.de with AVK MailGateway; for ; Wed, 16 Dec 2009 17:51:14 +0100 Content-class: urn:content-classes:message MIME-Version: 1.0 X-MimeOLE: Produced By Microsoft Exchange V6.5 Date: Wed, 16 Dec 2009 17:51:16 +0100 Message-ID: <38A51B74B884D74083D7950AD0DD85E828ACB3@File-Server-HST.hst.e-technik.tu-darmstadt.de> In-Reply-To: <88FB4290CF234F66933047AD790B3719@JimPC> X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: LF: Noise cancelling by using optic transmission of RX signals Thread-Index: Acp+VTLTYyAIoSUITii030LHU+fnswADmhLQ From: =?iso-8859-1?Q?Stefan_Sch=E4fer?= To: X-AVK-Virus-Check: AVB 19.626;16.12.2009 X-PMX-TU: seen v0.99a by 5.5.8.383112, Antispam-Engine: 2.7.2.376379, Antispam-Data: 2009.12.16.163919 X-PMX-SPAMCHECK: outgoing mail X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Content-Type: multipart/alternative; boundary="----_=_NextPart_001_01CA7E6F.FA862F49" Subject: LF: Noise cancelling by using optic transmission of RX signals 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_FONTCOLOR_UNKNOWN,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-IP: 193.82.116.20 X-Mailer: Unknown (No Version) ------_=_NextPart_001_01CA7E6F.FA862F49 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Dear Lowfers,=20 I want to start a new subject (for me it's new)... The last weeks I still had RX problems, either with the tx antenna or with= the short E-flied RX antenna. I found out that the noise was/is generated by my notebook which made RXin= g difficult, even in regions without any else local QRM (what could almost= bring me to shut down the PC and just do nice and easy CW QSOs without an= ything else! (but most traffic is in QRSS...)). Then I have done mni tests with many many ferrite cores (that I found in= an older emc lab in our institute), e.g. 20x FT50-77 plus 20x FT50-43 plu= s 20x FT50-61 and e few others. I placed them all in series, partly in the= near of the preamp and/or in the near of the RX. Sure, there was a signif= icant reduction of noise but lastly the noise remains.=20 Accidentally, during a test with my VFO connected to the same 12V supply= of my preamp, I observed a strong line in the argo monitor EVEN without= an antenna (short wire) connected to the VFO and when turned the amplitud= e to zero! That meant for me, the VFO and its supply is not suppressed eno= ugh and so some RF comes to the preamp by the coax and supply line! (the= preamp is supplied by a battery). I thought, I can use this (normally unw= anted) coupling path to test the blocking capability of the ferrite cores= and so I tried it with all variations and later with an additional BIG fe= rrite core and many turns of RG174. As I meant, surely there is a signific= ant noise reduction but the line in argo was still well visible! What I have done then (since 4 days) is using a coupling link by an optic= transmission of the 137kHz signal between the preamp and my RX using a SF= H750V as= the TX Diode and a SFH350 as the RX and abt 20m of a fiber optic cable (yes, there= are surely more suited components but these were available in the moment)= . These are also used as optic links into high end audio systems and there= fore easy to get... Now, when placing the preamp on the same place then during the tests befor= e and just changing the coax by the fiber optic cable, the line by the VFO= was completely gone!! Just with an antenna connected to the VFO and high= amplitude (and thus e real near-field "connection") it came back. The ove= rall noise level decreased to its absolute minimum during all the tests.= =20 Before I used this optic cable the only signal that could be received (out= of the city with much much qrm) was DCF39 and DLF and so on. Now, DCF39= came out with much better SNR and I saw the first LF Stn at all, it was= Ossi / OE5ODL transmitting his 5s in the evening (tnx! very nice SNR in= QRSS3 mode). My conclusion is, that the qrm is always brought to the very sensitive E-f= ield antenna by the coax, even when doing many usual suppression methods= cause there always remains a residual coupling impedance between both sid= es of the cable. Furthermore a long coax cable, say 20m away from the shac= k carries some qrm to the near of the rx antenna so the effective distance= to the shack is always reduced. One small disadvantage of this method is the need for a battery supply. My= TX diode needs abt 20mA and is now working since 3 days with a 7AH Lead= Acid battery. In the future I plan to use a stereo optic cable. Then, one= could switch the preamp on and off by the seconds line doing it the oppos= ite way. So, smaller batteries could be used, which is necessary when moun= ting the preamp to a shaky fiber mast if one does not want to change the= batteries each few hours ;-) Signal distortion seems to be no problem, as I can confirm until now. Now, my K2 has an optical LF input! ;-) Perhaps this will give some ideas to the local qrm bothered stns who tried= everything with ferrite cores, isolating transformers and so on without= a satisfying result. NOTE: I do not know if anyone has tried this before and has written a publ= ication about that. My goal is not to be the hero in inventions, to become= popular and especially not to compete with anyone (like it seems to be us= ual in career/job to be the one who gets the pay rise) but just to share= my ideas to those who are interested to try something new (?). I do not= say that my solution is the best at all and so on! But, if it will help= only one Lowfer getting new ideas and improving his station, and if this= improvement results in more activity on the band, then it would have help= ed all of us! =20 =20 73s es 55 de Stefan / DK7FC ------_=_NextPart_001_01CA7E6F.FA862F49 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable

Dear Lowfers,

= I want to start a new subject (for me it's new)...

= The last weeks I still had RX problems, either with the tx antenna or with the short E-fl= ied RX antenna.

= I found out that the noise was/is generated by my notebook which made RXing difficult,= even in regions without any else local QRM (what could almost bring me to shut= down the PC and just do nice and easy CW QSOs without anything else! (but most traffic is in QRSS...)).

= Then I have done mni tests with many many ferrite cores (that I found in an older emc= lab in our institute), e.g. 20x FT50-77 plus 20x FT50-43 plus 20x FT50-61 and= e few others. I placed them all in series, partly in the near of the preamp and/= or in the near of the RX. Sure, there was a significant reduction of noise but= lastly the noise remains.

= Accidentally, during a test with my VFO connected to the same 12V supply of my preamp,= I observed a strong line in the argo monitor EVEN without an antenna (short wire) connected to the VFO and when turned the amplitude to zero! That meant for= me, the VFO and its supply is not suppressed enough and so some RF comes to the pr= eamp by the coax and supply line! (the preamp is supplied by a battery). I thou= ght, I can use this (normally unwanted) coupling path to test the blocking capabi= lity of the ferrite cores and so I tried it with all variations and later with= an additional BIG ferrite core and many turns of RG174. As I meant, surely th= ere is a significant noise reduction but the line in argo was still well visib= le!

= What I have done then (since 4 days) is using a coupling link by an optic transmission= of the 137kHz signal between the preamp and my RX using a SFH750V as the TX Diode and a SFH350 as the RX and abt 20m of a fiber optic cable (yes, there are surely more= suited components but these were available in the moment). These are also used as optic links into high end audio systems and therefore easy to get...

= Now, when placing the preamp on the same place then during the tests before and just changing the coax by the fiber optic cable, the line by the VFO was comple= tely gone!! Just with an antenna connected to the VFO and high amplitude (and= thus e real near-field “connection”) it came back. The overall noise= level decreased to its absolute minimum during all the tests.

= Before I used this optic cable the only signal that could be received (out of the city= with much much qrm) was DCF39 and DLF and so on. Now, DCF39 came out with much better SNR and I saw the first LF Stn at all, it was Ossi / OE5ODL transmi= tting his 5s in the evening (tnx! very nice SNR in QRSS3 mode).

= My conclusion is, that the qrm is always brought to the very sensitive E-field antenna= by the coax, even when doing many usual suppression methods cause there always re= mains a residual coupling impedance between both sides of the cable. Furthermore= a long coax cable, say 20m away from the shack carries some qrm to the near= of the rx antenna so the effective distance to the shack is always reduced.

= One small disadvantage of this method is the need for a battery supply. My TX diode needs abt 20m= A and is now working since 3 days with a 7AH Lead Acid battery. In the future I= plan to use a stereo optic cable. Then, one could switch the preamp on and off= by the seconds line doing it the opposite way. So, smaller batteries could be used, which is necessary when mounting the preamp to a shaky fiber mast if= one does not want to change the batteries each few hours ;-)

= Signal distortion seems to be no problem, as I can confirm until now.

= Now, my K2 has an optical LF input! ;-)

= Perhaps this will give some ideas to the local qrm bothered stns who tried everything= with ferrite cores, isolating transformers and so on without a satisfying resul= t.

NOTE:= I do not know if anyone has tri= ed this before and has written a publication about that. My goal is not to be the hero in inventions, to become popular and especially not to compete with anyone (like it= seems to be usual in career/job to be the one who gets the pay rise) but just to share my ideas to those who are interested to try something new (?). I do= not say that my solution is the best at all and so on! But, if it will help on= ly one Lowfer getting new ideas and improving his station, and if this improv= ement results in more activity on the band, then it would have helped all of us!=

=  

=  

= 73s es 55 de Stefan / DK7FC

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