Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-md04.r1000.mx.aol.com (Internet Inbound) with ESMTP id 42BE8380001A7; Wed, 17 Aug 2011 12:19:47 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1QtipS-0000dm-VL for rs_out_1@blacksheep.org; Wed, 17 Aug 2011 17:18:54 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1QtipS-0000dd-6w for rsgb_lf_group@blacksheep.org; Wed, 17 Aug 2011 17:18:54 +0100 Received: from out1.ip03ir2.opaltelecom.net ([62.24.128.239]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1QtipP-0000HX-Jv for rsgb_lf_group@blacksheep.org; Wed, 17 Aug 2011 17:18:54 +0100 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AtAAAKHpS05cHYkx/2dsb2JhbABCgk2Be5BLhASPV3iBOwUBAQUIAQEDFgopAiwBAQMFAgEDEQQBAQohAgIUAQQaBhYIBhMKAQICAQGHYQKkC5FrhTiBEASCUaE4 X-IronPort-AV: E=Sophos;i="4.68,240,1312153200"; d="scan'208,217";a="357152743" Received: from host-92-29-137-49.as13285.net (HELO xphd97xgq27nyf) ([92.29.137.49]) by out1.ip03ir2.opaltelecom.net with SMTP; 17 Aug 2011 17:18:44 +0100 Message-ID: <001f01cc5cf9$4b734780$0401a8c0@xphd97xgq27nyf> From: "mal hamilton" To: References: <68BE37BD69E54DEE89CEBA8E30E9B94E@PcMinto> <4E47FFE9.10100@iup.uni-heidelberg.de> <3ED8E5422F1F45DBB8186E9D9870AD63@PcMinto> <4E480E02.9020706@iup.uni-heidelberg.de> <938BF599006244949F6CDDB5BA91F347@PcMinto> <4E482FBD.7030402@freenet.de> <4E484183.9090805@iup.uni-heidelberg.de> <4E494A57.90105@freenet.de> <4E4956DA.1060201@iup.uni-heidelberg.de> <4E49643E.5090708@freenet.de> <4E496FF9.4040608@iup.uni-heidelberg.de> <0A4ED65EC3B244A3BD0DAD6ACFF43793@JimPC> <4E4A5597.4070709@iup.uni-heidelberg.de> <3746D901368F4C139E414F9110153EEE@JimPC> <4E4A9A1F.2060600@iup.uni-heidelberg.de> <1B55B625C3CD4D529EC361D9C5D79D96@JimPC> <4E4AD4C8.8000509@iup.uni-heidelberg.de> <4E4AEF31.5010306@iup.uni-heidelberg.de> <1FF2FAD9854F4890A338A9F862D93FE9@JimPC> <8CE2AD319756ED7-1C20-14370@Webmail-m104.sysops.aol.com> <4E4BC177.6050902@iup.uni-heidelberg.de> Date: Wed, 17 Aug 2011 17:18:26 +0100 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2600.0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2600.0000 X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: Re: LF: Ferrite RX antennas Content-Type: multipart/alternative; boundary="----=_NextPart_000_001C_01CC5D01.ACF29030" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: * X-Spam-Status: No, hits=1.1 required=5.0 tests=HTML_20_30, HTML_FONTCOLOR_UNKNOWN,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-SCOLL-SCORE: 0:2:480350208:93952408 X-AOL-SCOLL-URL_COUNT: 0 x-aol-sid: 3039ac1d60584e4bea236cc8 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_001C_01CC5D01.ACF29030 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Stefan But what sort of strength do you Receive weak Radio Amateur signals. = That is the real test=20 Commercial radio stations a different matter with their Megawatts de mal/g3kev ----- Original Message -----=20 From: Stefan Sch=C3=A4fer=20 To: rsgb_lf_group@blacksheep.org=20 Sent: Wednesday, August 17, 2011 2:26 PM Subject: Re: LF: Ferrite RX antennas Hello Markus, Jim, LF,=20 Tnx for suggestions. Have to think about that later. I want to go on = in small steps now.=20 I added a 100 pF vari-cap which allows to resonate in the desired = range (up to 137.8 kHz and down to 136.3). As a first test a added a small winding, just 3 turns, 3 cm far for = the rods end, matched to 50 Ohm. So now it works as a passive antenna = and can be fed to my RX 50 Ohm input. This is the complete LF RX arrangement, suitable to see and hear on = 137 wideband: http://dl.dropbox.com/u/19882028/LF/LF-P%20RX%20RIG.JPG The ferrite antenna is just as broad a the netbook now. Of course the = distance to the netbook must be increased later. It still has no = electric shield but a suitable housing to protect the Litz winding, = necessary to go on with tests on various locations. The DCF-39 strength is 50 dB S/N in 1 Hz while the antenna (3 dB = bandwidth =3D 280 Hz) is tuned to 137.0 kHz (cannot tune to 138.83). The = band noise within the passband is 10 dB above the soundcards noise but = this may be different in a quiet location on a quiet day. This looks all promising to me. I'll try the BF862 as a preamp soon. Will do further tests with a test signal in the passband and compare = this to my 1m diameter single turn loop. And i will try my 50 Ohm preamp = in front of the RX. Looking forward to the first QSOs! 73, Stefan/DK7FC Am 17.08.2011 10:59, schrieb Markus Vester:=20 Stefan, Jim, you could increase the signal bandwidth without compromising SNR by = connecting a low impedance preamplifier. This technique has been used = widely and successfully in magnetic resonance imaging ("preamp = decoupling"). The preamp is designed to have an input impedance that = differs largely from the noise-optimum source impedance, so that you can = preserve the noise match but create an intentional signal mismatch. In practice, you would still want to use a low-noise FET connected = to the high impedance point of a parallel resonant antenna. Normally the = gate input impedance (megohms) is higher than the noise optimum (tens of = kiloohms), so you would have no preamp damping at all. The trick is then = to lower the input impedance by lossless feedback, which has neglegible = effect on the noise parameters.=20 One configuration is a compromise between common source and common = gate circuit configuration ("Zwischenbasisschaltung"), which can be = realised by inserting an additional negative-feedback winding in the = source-to-ground path. This is similar to the old regenerative audion, = but with the feedback coil polarity reversed. Another configuration is = parallel feedback from drain to gate, by intentionally increasing the = Miller capacitance. Best regards, Markus (DF6NM) -----Urspr=C3=BCngliche Mitteilung-----=20 Von: James Moritz An: rsgb_lf_group Verschickt: Mi, 17 Aug 2011 1:13 am Betreff: Re: LF: Ferrite RX antennas Dear Stefan, Looking good so far... A Q of 486 is certainly reaching the point where it becomes inconvenient = -=20 but remember that it is easy to reduce Q (probably connecting a preamp,=20 putting it in a container, etc, will reduce Q a bit anyway), and that = the=20 higher Q is, the better the SNR. So I would test it as an antenna with a = preamp - if there is more SNR than you need, you could experiment with = some=20 damping resistance. Cheers, Jim Moritz 73 de M0BMU=20 ------=_NextPart_000_001C_01CC5D01.ACF29030 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable =EF=BB=BF
Stefan
But what sort of strength do you Receive weak = Radio=20 Amateur signals. That is the real test
Commercial radio stations a different matter = with their=20 Megawatts
de mal/g3kev
 
----- Original Message -----
From:=20 Stefan Sch=C3=A4fer =
Sent: Wednesday, August 17, = 2011 2:26=20 PM
Subject: Re: LF: Ferrite RX=20 antennas

Hello Markus, Jim, LF,

Tnx for suggestions. = Have to=20 think about that later. I want to go on in small steps now.

I = added a=20 100 pF vari-cap which allows to resonate in the desired range (up to = 137.8 kHz=20 and down to 136.3).
As a first test a added a small winding, just 3 = turns,=20 3 cm far for the rods end, matched to 50 Ohm. So now it works as a = passive=20 antenna and can be fed to my RX 50 Ohm input.
This is the complete = LF RX=20 arrangement, suitable to see and hear on 137 wideband: http://d= l.dropbox.com/u/19882028/LF/LF-P%20RX%20RIG.JPG

The=20 ferrite antenna is just as broad a the netbook now. Of course the = distance to=20 the netbook must be increased later. It still has no electric shield = but a=20 suitable housing to protect the Litz winding, necessary to go on with = tests on=20 various locations.

The DCF-39 strength is 50 dB S/N in 1 Hz = while the=20 antenna (3 dB bandwidth =3D 280 Hz) is tuned to 137.0 kHz (cannot tune = to=20 138.83). The band noise within the passband is 10 dB above the = soundcards=20 noise but this may be different in a quiet location on a quiet=20 day.

This looks all promising to me. I'll try the BF862 as a = preamp=20 soon.

Will do further tests with a test signal in the passband = and=20 compare this to my 1m diameter single turn loop. And i will try my 50 = Ohm=20 preamp in front of the RX.
Looking forward to the first = QSOs!

73,=20 Stefan/DK7FC

Am 17.08.2011 10:59, schrieb Markus Vester:=20
Stefan, Jim,
 
you could increase the signal bandwidth without compromising = SNR by=20 connecting a low impedance preamplifier. This technique has = been used=20 widely and successfully in magnetic resonance imaging ("preamp=20 decoupling"). The preamp is designed to have an input impedance = that=20 differs largely from the noise-optimum source impedance, so that you = can=20 preserve the noise match but create an intentional signal = mismatch.
 
In practice, you would still want to use a = low-noise FET=20 connected to the high impedance point of a parallel resonant = antenna.=20 Normally the gate input impedance (megohms) is higher than the = noise=20 optimum (tens of kiloohms), so you would have no preamp damping at = all. The=20 trick is then to lower the input impedance by lossless = feedback, which=20 has neglegible effect on the noise parameters.
 
One configuration is a compromise between common source and = common gate=20 circuit configuration ("Zwischenbasisschaltung"), which can be = realised=20 by inserting an additional negative-feedback winding in the = source-to-ground=20 path. This is similar to the old regenerative audion, = but=20 with the feedback coil polarity reversed. Another configuration is = parallel=20 feedback from drain to gate, by intentionally increasing the Miller=20 capacitance.

Best regards,
Markus (DF6NM)
-----Urspr=C3=BCngliche=20 Mitteilung-----
Von: James Moritz <james.moritz@btopenworld= .com>
An:=20 rsgb_lf_group <rsgb_lf_group@blacksheep= .org>
Verschickt:=20 Mi, 17 Aug 2011 1:13 am
Betreff: Re: LF: Ferrite RX = antennas

Dear Stefan,

Looking good so far...

A Q of 486 is certainly reaching the point where it becomes inconvenient =
-=20
but remember that it is easy to reduce Q (probably connecting a preamp,=20
putting it in a container, etc, will reduce Q a bit anyway), and that =
the=20
higher Q is, the better the SNR. So I would test it as an antenna with a =

preamp - if there is more SNR than you need, you could experiment with =
some=20
damping resistance.

Cheers, Jim Moritz
73 de M0BMU=20
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