Return-Path: Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-da01.r1000.mx.aol.com (Internet Inbound) with ESMTP id 3116D380000B7; Sun, 7 Oct 2012 11:31:15 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1TKsoO-0006f0-Is for rs_out_1@blacksheep.org; Sun, 07 Oct 2012 16:30:36 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1TKsoN-0006er-VT for rsgb_lf_group@blacksheep.org; Sun, 07 Oct 2012 16:30:35 +0100 Received: from relay.uni-heidelberg.de ([129.206.100.212]) by relay1.thorcom.net with esmtps (TLSv1:AES256-SHA:256) (Exim 4.77) (envelope-from ) id 1TKsoJ-00038n-Su for rsgb_lf_group@blacksheep.org; Sun, 07 Oct 2012 16:30:34 +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 q97FUTLN004172 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO) for ; Sun, 7 Oct 2012 17:30:29 +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 q97FUT6c020349 for ; Sun, 7 Oct 2012 17:30:29 +0200 Message-ID: <5071A00F.4020506@iup.uni-heidelberg.de> Date: Sun, 07 Oct 2012 17:30:23 +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: <5070C574.4030005@iup.uni-heidelberg.de> <0C7651504C4A4734972F6FEAAB324A6A@AGB> In-Reply-To: <0C7651504C4A4734972F6FEAAB324A6A@AGB> X-Spam-Score: -2.8 (--) 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: Hi Graham, Am 07.10.2012 12:52, schrieb Graham: > Series tuned L/C cct 1.1 Mhz to shunt the probe ae ? Yes, that's what i want to do today. It's a very nice sunny day and i'm looking forward to climb on the roof now again :-) I thought about a series LC across the drain-source of the first JFET, to force it not to saturate on the output. [...] Content analysis details: (-2.8 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -0.7 RCVD_IN_DNSWL_LOW RBL: Sender listed at http://www.dnswl.org/, low trust [129.206.100.212 listed in list.dnswl.org] -2.1 RP_MATCHES_RCVD Envelope sender domain matches handover relay domain 0.0 HTML_MESSAGE BODY: HTML included in message X-Scan-Signature: f9bb43a66658129469273581af35b296 Subject: Re: LF: GRRRRR!! Now i know... Content-Type: multipart/alternative; boundary="------------030309060801060501040402" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: * X-Spam-Status: No, hits=1.0 required=5.0 tests=HTML_20_30,HTML_MESSAGE, HTML_TITLE_EMPTY 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: 3039ac1d40495071a04305eb X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none This is a multi-part message in MIME format. --------------030309060801060501040402 Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: quoted-printable X-MIME-Autoconverted: from 8bit to quoted-printable by relay.uni-heidelberg.de id q97FUTLN004172 Hi Graham, Am 07.10.2012 12:52, schrieb Graham: > Series tuned L/C cct 1.1 Mhz to shunt the probe ae ? Yes, that's what i want to do today. It's a very nice sunny day and i'm=20 looking forward to climb on the roof now again :-) I thought about a series LC across the drain-source of the first JFET,=20 to force it not to saturate on the output. > .but is the probe saturated ? Yes, that's the question. Maybe the saturation happens in the 2nd stage=20 only. One idea may be to rise the supply voltage from now 11V to 14V or=20 so (the input JFET is a BF862 which makes a high gain!) which may help=20 the first stage not to saturate, if this is the case at all. If IM is generated in the 2nd stage (currently a 2N3053 (is that a good=20 idea??? ), a simple LC LPF would be OK. I'm not interested in=20 frequencies above 600 kHz. > ... but with high signal levels any rusty bolt in any =20 > metal structure is a noise source GRRR, once again ;-) But soon they are QRT... Tnx and 73, Stefan > G.. > > *From:* Stefan Sch=E4fer > *Sent:* Sunday, October 07, 2012 12:57 AM > *To:* rsgb_lf_group@blacksheep.org > *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=20 > kHz. Now as i installed the new wideband LF/MF probe i got even more=20 > QRM. The design is not so far from the PA0RDT design. After increasing=20 > the antenna by another meter on the top of the roof i got worse=20 > signals than before. > > Yesterday i found that it must be a resonance on the cable since i=20 > could reduce the effect dramatically by adding a 1 nF C and a 1 kOhm R=20 > on the RX end. > But i still saw IM. This was the problem with all my previous=20 > antennas. The signals levels are close to the noise floor but when i=20 > increased the probe C it became worse.... > > Now i checked this oscillation on an oscilloscope. By adding some C or=20 > R i could reduce the amplitude of the signal but never the frequency,=20 > which is strange. Then i noticed that it is AM !!!!! So it must be a=20 > transmitter very close to me since the signal levels were 4V pp here,=20 > and this started to cause noticable IM on LF and MF. > > I checked the web with some keywords like "radio" and "heidelberg" and=20 > quickly found this > > It is AFN in Heidelberg on *1143 kHz*. This is a *AM transmitter=20 > 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:=20 > http://www.afneurope.net/Home/ArticleDisplayDD/tabid/649/Default.aspx?a= id=3D25644 > > So now, that may explain why my RX site often suffered from QRM. And=20 > that explains why a resonated circuit in front of the first active=20 > 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=20 > the difference in the noise background when they go off. For now i=20 > need some kind of filter and i have to take care that the input of the=20 > first JFET does not become overloaded. > > Will go on investigating!... > > 73, Stefan/DK7FC --------------030309060801060501040402 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 q97FUTLN004172 Hi Graham,

Am 07.10.2012 12:52, schrieb Graham:
Series=A0=A0 tuned=A0=A0 L/C=A0=A0 cct=A0 1.1 Mhz=A0=A0 to=A0 shun= t the=A0 probe=A0 ae=A0 ?
Yes, that's what i want to do today. It's a very nice sunny day and i'm looking forward to climb on the roof now again :-)
I thought about a series LC across the drain-source of the first JFET, to force it not to saturate on the output.

.but is the=A0 probe=A0 saturated=A0 ?
Yes, that's the question. Maybe the saturation happens in the 2nd stage only. One idea may be to rise the supply voltage from now 11V to 14V or so (the input JFET is a BF862 which makes a high gain!) which may help the first stage not to saturate, if this is the case at all.
If IM is generated in the 2nd stage (currently a 2N3053 (is that a good idea??? ), a simple LC LPF would be OK. I'm not interested in frequencies above 600 kHz.

... but=A0 with=A0 high=A0=A0 signal=A0 levels=A0=A0 any=A0 rusty= =A0 bolt=A0 in any=A0 metal=A0 structure is=A0 a noise=A0 source=A0
GRRR, once again ;-) But soon they are QRT...

Tnx and 73, Stefan


=A0
G..

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.

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://w= ww.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/6= 49/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
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