Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-ma02.r1000.mx.aol.com (Internet Inbound) with ESMTP id B0C7138000086; Wed, 17 Aug 2011 19:18:11 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1QtpLk-0002wH-K2 for rs_out_1@blacksheep.org; Thu, 18 Aug 2011 00:16:40 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1QtpLj-0002w8-Bt for rsgb_lf_group@blacksheep.org; Thu, 18 Aug 2011 00:16:39 +0100 Received: from out1.ip08ir2.opaltelecom.net ([62.24.128.244]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1QtpLg-0007Yl-V7 for rsgb_lf_group@blacksheep.org; Thu, 18 Aug 2011 00:16:39 +0100 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AtcAAFFLTE5cF/WG/2dsb2JhbABCgk2BfJRRj1d4gTsFAQEFCAEBAxYKKQITCRABAQMFAgEDEQQBAQohAgIUAQQaBhYIBhMKAQICAQGHYQKlEJFPhTiBEASCUaE4 X-IronPort-AV: E=Sophos;i="4.68,242,1312153200"; d="scan'208,217";a="499324119" Received: from host-92-23-245-134.as13285.net (HELO xphd97xgq27nyf) ([92.23.245.134]) by out1.ip08ir2.opaltelecom.net with SMTP; 18 Aug 2011 00:16:29 +0100 Message-ID: <002501cc5d33$a7f37f90$0401a8c0@xphd97xgq27nyf> From: "mal hamilton" To: References: <68BE37BD69E54DEE89CEBA8E30E9B94E@PcMinto> <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> <4E4C24FE.8030905@iup.uni-heid elberg.de> Date: Thu, 18 Aug 2011 00:16:12 +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_0022_01CC5D3C.095AD370" 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: 1:2:478407232:93952408 X-AOL-SCOLL-URL_COUNT: 1 x-aol-sid: 3039ac1d600a4e4c4c33232d 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_0022_01CC5D3C.095AD370 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Stefan Excellent performance for a small ferrite rx antenna.=20 You mention that the loop is better than the ferrite antenna possibly = because physically the loop has a larger signal capture area. 73 es gl=20 de mal/g3kev ----- Original Message -----=20 From: Stefan Sch=C3=A4fer=20 To: rsgb_lf_group@blacksheep.org=20 Sent: Wednesday, August 17, 2011 9:30 PM Subject: Re: LF: Ferrite RX antennas Mal, LF,=20 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/G3KEV_on_ferrite_antenna.png Signal was audible as well: = 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 = ferrite antenna was just 20 cm above the ground/soil and 30m RG58 in = between. I used the 50 Ohm preamp during that test.=20 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:=20 ok Stefan Nw CQ 137.7 can u receive me=20 de mal/g3kev ----- Original Message -----=20 From: Stefan Sch=C3=A4fer=20 To: rsgb_lf_group@blacksheep.org=20 Sent: Wednesday, August 17, 2011 5:55 PM Subject: Re: LF: Ferrite RX antennas Mal,=20 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:=20 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_0022_01CC5D3C.095AD370 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable =EF=BB=BF
Stefan
Excellent performance for a small ferrite rx = antenna.=20
You mention that the loop is better than the = ferrite=20 antenna possibly because physically the loop has a larger signal capture = area.
73 es gl
de mal/g3kev
 
----- Original Message -----
From:=20 Stefan Sch=C3=A4fer =
Sent: Wednesday, August 17, = 2011 9:30=20 PM
Subject: Re: LF: Ferrite RX=20 antennas

Mal, LF,

Back from /p from JN49IV75ORMal, you=20 are the sceptic on ferrite antennas, so pse fasten your seat belt = before you=20 take a look on this picture: http://dl.dropbox.com/u/19882028/LF/G3KEV_on_ferrite_antenna.png
=
Signal=20 was audible as well: http://dl.dropbox.com/u/19882028/LF/G3KEV_audible_on_ferrite_ant= enna.WAV
QRB=20 is 796 km.
Critical for a fast CW QSO but it is evening and QRN was = high.=20 The 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=20 the picture: Sferics are strongest arround 137.7, due to the high = antenna Q.=20 There was a frequency offset of about 10 Hz but never mind. Below = 137.5 kHz i=20 assume this is WSPR by PA0A?

A comparison between the 1 m = diameter=20 single turn loop was done. Both antennas were adjusted to minimise = DCF39. My=20 own test signal out of 53.8 km was up to 55 dB S/N in 1 Hz on the loop = without=20 a preamp, audible of course. On the ferrite antenna + preamp it was 55 = dB S/N=20 too! But there must have been QSB due to a skywave component. Hasn't = been the=20 best time for that test.

Both antennas can't be accurately = resonated at=20 138.8 kHz, and have different Q. The ferrite antenna has about twice = the Q of=20 the loop. When using the loop + preamp, the ADC gets heavyly = overloaded.=20 Without a 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=20 tests soon but this ferrite antenna seems to become a really useful=20 alternative to any other large antenna. It is very well /p and=20 /m.

Looking forward to further improvements and first QSOs. = Glad to=20 have realised that project in a few days after starting the discussion = :-))

If someone follows the discussion and thinks about = building such=20 an antenna too, just ask if you have questions that weren't discussed = so far.=20 Maybe this will lead us to new ideas.

Ah, BTW, still no E field = shield.=20 Do the experts really think that this is necessary? I mean, because i = will=20 ever use it in a quiet location!

73, = Stefan/DK7FC



Am=20 17.08.2011 20:02, schrieb mal hamilton:=20
ok Stefan
Nw CQ 137.7 can u receive me
de mal/g3kev
 
-----=20 Original Message ----- From:=20 Stefan=20 Sch=C3=A4fer To:=20 rsgb_lf_group@blacksheep.org Sent:=20 Wednesday, August 17, 2011 5:55 PM Subject:=20 Re: LF: Ferrite RX antennas

Mal,

I know. But anyway one can compare the = SNR=20 levels between different antennas.

I'll set up a beacon now = on=20 137.73 kHz, testing in QRSS-3.
Maybe you want to call CQ or so. = If i=20 can receive you, i will send a capture. But i still cannot answer. = Am in=20 Darmstadt now, not in Heidelberg. The UHF link for transmitting = works just=20 in a range of 5 km and is disabled now.

I expect that i = need a=20 preamp and will not get the necessary sensitivy now. Anyway i can = compare=20 the antennas and check how many dBs are missed.

RX QRV in = half an=20 hour. Beacon starting at 17:30 UTC

73, = Stefan/DK7FC

Am=20 17.08.2011 18:18, schrieb mal hamilton:=20
Stefan
But what sort of strength do you Receive = weak=20 Radio Amateur signals. That is the real test
Commercial radio stations a different = matter with=20 their Megawatts
de mal/g3kev
 
-----=20 Original Message ----- From:=20 Stefan Sch=C3=A4fer To:=20 rsgb_lf_group@blacksheep.org = Sent:=20 Wednesday, August 17, 2011 2:26 PM Subject:=20 Re: LF: Ferrite RX antennas

Hello Markus, Jim, LF,

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

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

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

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

Will do=20 further tests with a test signal in the passband and compare = this to=20 my 1m diameter single turn loop. And i will try my 50 Ohm = preamp in=20 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=20 SNR by connecting a low impedance preamplifier. This = technique=20 has been used widely and successfully in magnetic resonance = imaging=20 ("preamp decoupling"). The preamp is designed to have = an input=20 impedance that differs largely from the noise-optimum source = impedance, so that you can preserve the noise match but = create an=20 intentional signal mismatch.
 
In practice, you would still want to use = a=20 low-noise FET connected to the high impedance point of a = parallel=20 resonant antenna. Normally the gate input impedance = (megohms)=20 is higher than the noise optimum (tens of kiloohms), so = you=20 would have no preamp damping at all. The trick is then = to lower=20 the input impedance by lossless feedback, which has = neglegible=20 effect on the noise parameters.
 
One configuration is a compromise between common source = and=20 common gate circuit configuration = ("Zwischenbasisschaltung"),=20 which can be realised by inserting an additional=20 negative-feedback winding in the source-to-ground = path. This is=20 similar to the old regenerative audion, but with = the=20 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: = rsgb_lf_group <rsgb_lf_group@blacksheep.org>
Vers= chickt:=20 Mi, 17 Aug 2011 1:13 am
Betreff: Re: LF: Ferrite RX=20 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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