Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-mk04.r1000.mx.aol.com (Internet Inbound) with ESMTP id 11F4C380000E4; Wed, 17 Aug 2011 16:32:13 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1QtmlM-0001yB-Tt for rs_out_1@blacksheep.org; Wed, 17 Aug 2011 21:30:56 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1QtmlL-0001y2-Tu for rsgb_lf_group@blacksheep.org; Wed, 17 Aug 2011 21:30:55 +0100 Received: from relay.uni-heidelberg.de ([129.206.100.212]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1QtmlK-0004lq-6C for rsgb_lf_group@blacksheep.org; Wed, 17 Aug 2011 21:30:55 +0100 Received: from ix.urz.uni-heidelberg.de (cyrus-portal.urz.uni-heidelberg.de [129.206.100.176]) by relay.uni-heidelberg.de (8.14.1/8.14.1) with ESMTP id p7HKUqdf029254 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO) for ; Wed, 17 Aug 2011 22:30:52 +0200 Received: from extmail.urz.uni-heidelberg.de (extmail.urz.uni-heidelberg.de [129.206.100.140]) by ix.urz.uni-heidelberg.de (8.13.8/8.13.8) with ESMTP id p7HKUqRQ022569 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO) for ; Wed, 17 Aug 2011 22:30:52 +0200 Received: from [129.206.205.192] (vpn205-192.rzuser.uni-heidelberg.de [129.206.205.192]) by extmail.urz.uni-heidelberg.de (8.13.4/8.13.1) with ESMTP id p7HKUoIc020764 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO) for ; Wed, 17 Aug 2011 22:30:51 +0200 Message-ID: <4E4C24FE.8030905@iup.uni-heidelberg.de> Date: Wed, 17 Aug 2011 22:30:54 +0200 From: =?UTF-8?B?U3RlZmFuIFNjaMOkZmVy?= User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; de; rv:1.9.1.11) Gecko/20100711 Thunderbird/3.0.6 MIME-Version: 1.0 To: rsgb_lf_group@blacksheep.org 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> <001f01cc5cf9$4b734780$0401a8c0@xphd97xgq27nyf> <4E4BF289.2070500@iup.uni-heidelberg.de> <003301cc5d07$d4e2a840$0401a8c0@xphd97xgq2! 7nyf> In-Reply-To: <003301cc5d07$d4e2a840$0401a8c0@xphd97xgq27nyf> X-Spam-Score: 1.4 (+) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001,RATWARE_GECKO_BUILD=1.426 Subject: Re: LF: Ferrite RX antennas Content-Type: multipart/alternative; boundary="------------000602010404000601010006" 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: 1:2:471354592:93952408 X-AOL-SCOLL-URL_COUNT: 1 x-aol-sid: 3039ac1d61884e4c254d1ce7 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none This is a multi-part message in MIME format. --------------000602010404000601010006 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable X-MIME-Autoconverted: from 8bit to quoted-printable by relay.uni-heidelberg.de id p7HKUqdf029254 Mal, LF, Back from /p from JN49IV75OR Mal, you are the sceptic on ferrite antennas, so pse fasten your seat=20 belt before you take a look on this picture:=20 http://dl.dropbox.com/u/19882028/LF/G3KEV_on_ferrite_antenna.png Signal was audible as well:=20 http://dl.dropbox.com/u/19882028/LF/G3KEV_audible_on_ferrite_antenna.WAV QRB is 796 km. Critical for a fast CW QSO but it is evening and QRN was high. The=20 ferrite antenna was just 20 cm above the ground/soil and 30m RG58 in=20 between. I used the 50 Ohm preamp during that test. Well visible in the picture: Sferics are strongest arround 137.7, due to=20 the high antenna Q. There was a frequency offset of about 10 Hz but=20 never mind. Below 137.5 kHz i assume this is WSPR by PA0A? A comparison between the 1 m diameter single turn loop was done. Both=20 antennas were adjusted to minimise DCF39. My own test signal out of 53.8=20 km was up to 55 dB S/N in 1 Hz on the loop without a preamp, audible of=20 course. On the ferrite antenna + preamp it was 55 dB S/N too! But there=20 must have been QSB due to a skywave component. Hasn't been the best time=20 for that test. Both antennas can't be accurately resonated at 138.8 kHz, and have=20 different Q. The ferrite antenna has about twice the Q of the loop. When=20 using the loop + preamp, the ADC gets heavyly overloaded. Without a=20 preamp the ferrite antenna performs about 15 dB worse than the loop.=20 This should be solved with a single JFET amp stage. Will do further tests soon but this ferrite antenna seems to become a=20 really useful alternative to any other large antenna. It is very well /p=20 and /m. Looking forward to further improvements and first QSOs. Glad to have=20 realised that project in a few days after starting the discussion :-)) If someone follows the discussion and thinks about building such an=20 antenna too, just ask if you have questions that weren't discussed so=20 far. Maybe this will lead us to new ideas. Ah, BTW, still no E field shield. Do the experts really think that this=20 is necessary? I mean, because i will ever use it in a quiet location! 73, Stefan/DK7FC Am 17.08.2011 20:02, schrieb mal hamilton: > ok Stefan > Nw CQ 137.7 can u receive me > de mal/g3kev > > ----- Original Message ----- > *From:* Stefan Sch=C3=A4fer > *To:* rsgb_lf_group@blacksheep.org > > *Sent:* Wednesday, August 17, 2011 5:55 PM > *Subject:* Re: LF: Ferrite RX antennas > > Mal, > > I know. But anyway one can compare the SNR levels between > different antennas. > > I'll set up a beacon now on 137.73 kHz, testing in QRSS-3. > Maybe you want to call CQ or so. If i can receive you, i will send > a capture. But i still cannot answer. Am in Darmstadt now, not in > Heidelberg. The UHF link for transmitting works just in a range of > 5 km and is disabled now. > > I expect that i need a preamp and will not get the necessary > sensitivy now. Anyway i can compare the antennas and check how > many dBs are missed. > > RX QRV in half an hour. Beacon starting at 17:30 UTC > > 73, Stefan/DK7FC > > Am 17.08.2011 18:18, schrieb mal hamilton: >> Stefan >> But what sort of strength do you Receive weak Radio Amateur >> signals. That is the real test >> Commercial radio stations a different matter with their Megawatts >> de mal/g3kev >> >> ----- Original Message ----- >> *From:* Stefan Sch=C3=A4fer >> *To:* rsgb_lf_group@blacksheep.org >> >> *Sent:* Wednesday, August 17, 2011 2:26 PM >> *Subject:* Re: LF: Ferrite RX antennas >> >> Hello Markus, Jim, LF, >> >> Tnx for suggestions. Have to think about that later. I want >> to go on in small steps now. >> >> 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: >>> 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. >>> 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----- >>> 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 i= nconvenient - >>> but remember that it is easy to reduce Q (probably connecting= a preamp, >>> putting it in a container, etc, will reduce Q a bit anyway), = and that the >>> higher Q is, the better the SNR. So I would test it as an ant= enna with a >>> preamp - if there is more SNR than you need, you could experi= ment with some >>> damping resistance. >>> >>> Cheers, Jim Moritz >>> 73 de M0BMU >>> >>> >> --------------000602010404000601010006 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-MIME-Autoconverted: from 8bit to quoted-printable by relay.uni-heidelberg.de id p7HKUqdf029254 Mal, LF,

Back from /p from JN49IV75OR Mal, you are the sceptic on ferrite antennas, so pse fasten your seat belt before you take a look on this picture: http://dl.dropbox.com/u/19882028/LF/G= 3KEV_on_ferrite_antenna.png

Signal was audible as well: http://dl.dropbox.com/u/19882= 028/LF/G3KEV_audible_on_ferrite_antenna.WAV
QRB is 796 km.
Critical for a fast CW QSO but it is evening and QRN was high. The ferrite antenna was just 20 cm above the ground/soil and 30m RG58 in between. I used the 50 Ohm preamp during that test.

Well visible in the picture: Sferics are strongest arround 137.7, due to the high antenna Q. There was a frequency offset of about 10 Hz but never mind. Below 137.5 kHz i assume this is WSPR by PA0A?

A comparison between the 1 m diameter single turn loop was done. Both antennas were adjusted to minimise DCF39. My own test signal out of 53.8 km was up to 55 dB S/N in 1 Hz on the loop without a preamp, audible of course. On the ferrite antenna + preamp it was 55 dB S/N too! But there must have been QSB due to a skywave component. Hasn't been the best time for that test.

Both antennas can't be accurately resonated at 138.8 kHz, and have different Q. The ferrite antenna has about twice the Q of the loop. When using the loop + preamp, the ADC gets heavyly overloaded. Without a preamp the ferrite antenna performs about 15 dB worse than the loop. This should be solved with a single JFET amp stage.

Will do further tests soon but this ferrite antenna seems to become a really useful alternative to any other large antenna. It is very well /p and /m.

Looking forward to further improvements and first QSOs. Glad to have realised that project in a few days after starting the discussion :-))
If someone follows the discussion and thinks about building such an antenna too, just ask if you have questions that weren't discussed so far. Maybe this will lead us to new ideas.

Ah, BTW, still no E field shield. Do the experts really think that this is necessary? I mean, because i will ever use it in a quiet location!

73, Stefan/DK7FC



Am 17.08.2011 20:02, schrieb mal hamilton:
ok Stefan
Nw CQ 137.7 can u receive me
de mal/g3kev
=C2=A0
----- Original Message -----
From: Stefan Sch=C3=A4fer <= /div>
Sent: Wednesday, August 17, 2011 5:55 PM
Subject: Re: LF: Ferrite RX antennas

Mal,

I know. But anyway one can compare the SNR levels between different antennas.

I'll set up a beacon now on 137.73 kHz, testing in QRSS-3.
Maybe you want to call CQ or so. If i can receive you, i will send a capture. But i still cannot answer. Am in Darmstadt now, not in Heidelberg. The UHF link for transmitting works just in a range of 5 km and is disabled now.

I expect that i need a preamp and will not get the necessary sensitivy now. Anyway i can compare the antennas and check how many dBs are missed.

RX QRV in half an hour. Beacon starting at 17:30 UTC

73, Stefan/DK7FC

Am 17.08.2011 18:18, schrieb mal hamilton:
Stefan
But what sort of strength do you Receive weak Radio Amateur signals. That is the real test
Commercial radio stations a different matter with their Megawatts
de mal/g3kev
=C2=A0
----- Original Message -----
Sent: Wednesday, August 17, 2011 2:26 PM
Subject: Re: LF: Ferrite RX antennas

Hello Markus, Jim, LF,

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

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%2= 0RIG.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:
Stefan, Jim,
=C2=A0
you could increase the signal bandwidth without compromising SNR by connecting a low impedance preamplifier.=C2=A0This technique has been used widely and successfully in magnetic resonance imaging ("preamp decoupling").=C2=A0The preamp is designed to have an inp= ut impedance that differs largely from the noise-optimum source impedance, so that you can preserve the noise match but create an intentional signal mismatch.
=C2=A0
In practice, you would=C2=A0still=C2=A0want to=C2=A0use a = low-noise FET connected to the high impedance point of a parallel resonant antenna. Normally the gate input impedance (megohms) is=C2=A0higher than the noise optimum (tens of kiloohms), so you would have no preamp damping at all. The trick is=C2=A0then to lower the input impedance by lossless feedback, which has neglegible effect on the noise=C2=A0parameters.
=C2=A0
One configuration is a compromise between common source and common gate circuit configuration ("Zwischenbasisschaltung"), which=C2=A0can be realised by inserting an additional negative-feedback winding in the source-to-ground path.=C2=A0This is similar to=C2=A0the old=C2=A0regenerative audion, but with the feedback coil polarity reverse= d. Another configuration is parallel feedback from drain to gate, by intentionally increasing the Miller capacitance.

Best regards,
Markus (DF6NM)
-= ----Urspr=C3=BCngliche Mitteilung-----
Von: James Moritz &l= t;james.moritz@btopenworld.com>
An: rsgb_lf_group &l= t;rsgb_lf_group@blacksheep.org>
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=20
preamp - if there is more SNR than you need, you could experiment with so=
me=20
damping resistance.

Cheers, Jim Moritz
73 de M0BMU=20
--------------000602010404000601010006--