Return-Path: Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-mk01.r1000.mx.aol.com (Internet Inbound) with ESMTP id 019E638000090; Sun, 7 Oct 2012 06:53:58 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1TKoTl-00040e-5w for rs_out_1@blacksheep.org; Sun, 07 Oct 2012 11:53:01 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1TKoTk-00040V-L9 for rsgb_lf_group@blacksheep.org; Sun, 07 Oct 2012 11:53:00 +0100 Received: from smtpout1.wanadoo.co.uk ([80.12.242.29] helo=smtpout.wanadoo.co.uk) by relay1.thorcom.net with esmtp (Exim 4.77) (envelope-from ) id 1TKoTh-0002X5-F6 for rsgb_lf_group@blacksheep.org; Sun, 07 Oct 2012 11:52:59 +0100 Received: from AGB ([2.26.21.21]) by mwinf5d13 with ME id 8Asw1k0060THXEA03AswZk; Sun, 07 Oct 2012 12:52:56 +0200 Message-ID: <0C7651504C4A4734972F6FEAAB324A6A@AGB> From: "Graham" To: References: <5070C574.4030005@iup.uni-heidelberg.de> In-Reply-To: <5070C574.4030005@iup.uni-heidelberg.de> Date: Sun, 7 Oct 2012 11:52:56 +0100 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal Importance: Normal X-Mailer: Microsoft Windows Live Mail 14.0.8117.416 X-MimeOLE: Produced By Microsoft MimeOLE V14.0.8117.416 X-Spam-Score: 0.0 (/) X-Spam-Report: Spam detection software, running on the system "relay1.thorcom.net", has identified this incoming email as possible spam. The original message has been attached to this so you can view it (if it isn't spam) or label similar future email. If you have any questions, see the administrator of that system for details. Content preview: Series tuned L/C cct 1.1 Mhz to shunt the probe ae ? .but is the probe saturated ? ... but with high signal levels any rusty bolt in any metal structure is a noise source G.. From: Stefan Schäfer Sent: Sunday, October 07, 2012 12:57 AM To: rsgb_lf_group@blacksheep.org Subject: LF: GRRRRR!! Now i know... [...] Content analysis details: (0.0 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at http://www.dnswl.org/, no trust [80.12.242.29 listed in list.dnswl.org] 0.0 HTML_MESSAGE BODY: HTML included in message X-Scan-Signature: 4998b3eda037fec4e885bebc9a2db934 Subject: Re: LF: GRRRRR!! Now i know... Content-Type: multipart/alternative; boundary="----=_NextPart_000_0040_01CDA482.4A308550" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.6 required=5.0 tests=HTML_20_30,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: 3039ac1d618550715f462b47 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none This is a multi-part message in MIME format. ------=_NextPart_000_0040_01CDA482.4A308550 Content-Type: text/plain; charset="ISO-8859-15" Content-Transfer-Encoding: quoted-printable Series tuned L/C cct 1.1 Mhz to shunt the probe ae ? .but = is the probe saturated ? ... but with high signal levels any = rusty bolt in any metal structure is a noise source =20 G.. From: Stefan Sch=E4fer=20 Sent: Sunday, October 07, 2012 12:57 AM To: rsgb_lf_group@blacksheep.org=20 Subject: LF: GRRRRR!! Now i know... Oh now, i can't belive it. Must tell you that: All the years i suffered from QRM which seemed to come from DLF at 153 = kHz. Now as i installed the new wideband LF/MF probe i got even more = QRM. The design is not so far from the PA0RDT design. After increasing = the antenna by another meter on the top of the roof i got worse signals = than before.=20 Yesterday i found that it must be a resonance on the cable since i could = reduce the effect dramatically by adding a 1 nF C and a 1 kOhm R on the = RX end. But i still saw IM. This was the problem with all my previous antennas. = The signals levels are close to the noise floor but when i increased the = probe C it became worse.... Now i checked this oscillation on an oscilloscope. By adding some C or R = i could reduce the amplitude of the signal but never the frequency, = which is strange. Then i noticed that it is AM !!!!! So it must be a = transmitter very close to me since the signal levels were 4V pp here, = and this started to cause noticable IM on LF and MF. I checked the web with some keywords like "radio" and "heidelberg" and = quickly found this It is AFN in Heidelberg on 1143 kHz. This is a AM transmitter running 1 = kW in about 1 km distance! http://www.asamnet.de/~bienerhj/1143-HD.html#1143-HD It is a 100m tower. I never noticed it since i live here, odd. Here one can read that AFN Heidelberg will be QRT on MF very soon: = http://www.afneurope.net/Home/ArticleDisplayDD/tabid/649/Default.aspx?aid= =3D25644 So now, that may explain why my RX site often suffered from QRM. And = that explains why a resonated circuit in front of the first active = device in my E field antennas were always the best solution for me! I don't want to wait until they go QRT but i'm looking forward to see = the difference in the noise background when they go off. For now i need = some kind of filter and i have to take care that the input of the first = JFET does not become overloaded. Will go on investigating!... 73, Stefan/DK7FC ------=_NextPart_000_0040_01CDA482.4A308550 Content-Type: text/html; charset="ISO-8859-15" Content-Transfer-Encoding: quoted-printable
Series   tuned   L/C   cct  1.1=20 Mhz   to  shunt the  probe  ae  ? .but is=20 the  probe  saturated  ? ... but  with =20 high   signal  levels   any  rusty =20 bolt  in any  metal  structure is  a noise =20 source 
 
G..

From: Stefan = Sch=E4fer
Sent: Sunday, October 07, 2012 12:57 AM
To: rsgb_lf_group@blacksheep.org= =20
Subject: LF: GRRRRR!! Now i know...

Oh now, i can't belive it. Must tell you that:

All = the=20 years i suffered from QRM which seemed to come from DLF at 153 kHz. Now = as i=20 installed the new wideband LF/MF probe i got even more QRM. The design = is not so=20 far from the PA0RDT design. After increasing the antenna by another = meter on the=20 top of the roof i got worse signals than before.

Yesterday i = found that=20 it must be a resonance on the cable since i could reduce the effect = dramatically=20 by adding a 1 nF C and a 1 kOhm R on the RX end.
But i still saw IM. = This was=20 the problem with all my previous antennas. The signals levels are close = to the=20 noise floor but when i increased the probe C it became = worse....

Now i=20 checked this oscillation on an oscilloscope. By adding some C or R i = could=20 reduce the amplitude of the signal but never the frequency, which is = strange.=20 Then i noticed that it is AM !!!!! So it must be a transmitter very = close to me=20 since the signal levels were 4V pp here, and this started to cause = noticable IM=20 on LF and MF.

I checked the web with some keywords like "radio" = and=20 "heidelberg" and quickly found this

It is AFN in Heidelberg on = 1143=20 kHz. This is a AM transmitter running 1 kW in about 1 km=20 distance!
http://www.= asamnet.de/~bienerhj/1143-HD.html#1143-HD
It=20 is a 100m tower. I never noticed it since i live here, odd.
Here one = can read=20 that AFN Heidelberg will be QRT on MF very soon: http://www.afneurope.net/Home/ArticleDisplayDD/tabid/64= 9/Default.aspx?aid=3D25644

So=20 now, that may explain why my RX site often suffered from QRM. And that = explains=20 why a resonated circuit in front of the first active device in my E = field=20 antennas were always the best solution for me!

I don't want to = wait until=20 they go QRT but i'm looking forward to see the difference in the noise=20 background when they go off. For now i need some kind of filter and i = have to=20 take care that the input of the first JFET does not become=20 overloaded.

Will go on investigating!...

73,=20 Stefan/DK7FC
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