Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-mg02.r1000.mx.aol.com (Internet Inbound) with ESMTP id 6EAE9380001DC; Thu, 29 Sep 2011 16:13:26 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1R9Mxj-0005Ke-UQ for rs_out_1@blacksheep.org; Thu, 29 Sep 2011 21:12:07 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1R9Mxi-0005KV-9S for rsgb_lf_group@blacksheep.org; Thu, 29 Sep 2011 21:12:06 +0100 Received: from mta-13.siol.net ([193.189.160.143]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1R9Mxg-0000UW-82 for rsgb_lf_group@blacksheep.org; Thu, 29 Sep 2011 21:12:06 +0100 Received: from mail-7.siol.net ([10.10.10.108]) by mta-13.siol.net with ESMTP id <20110929201202.MBQG6018.mta-13.siol.net@mail-7.siol.net> for ; Thu, 29 Sep 2011 22:12:02 +0200 Received: from konda03bf4520e ([89.142.134.88]) by mail-7.siol.net with SMTP id <20110929201201.IUQT6172.mail-7.siol.net@konda03bf4520e> for ; Thu, 29 Sep 2011 22:12:01 +0200 Message-ID: <8F0D3FDDD6414BE8AC65D5D4B1CFDF1F@konda03bf4520e> From: "Joze Konda - S52AB" To: References: <68BE37BD69E54DEE89CEBA8E30E9B94E@PcMinto> <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$0401a8c0@xphd97xgq2! 7nyf> <4E4C24FE.8030905@iup.uni-hei! delberg.de> <002501cc5d33$a7f37f90$0401a8c0@xphd97xgq27nyf> <4E84C757.2040605@iup.u ni-heidelberg.de> Date: Thu, 29 Sep 2011 22:11:57 +0200 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.5931 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5994 X-Cloudmark-Analysis: v=1.1 cv=I8HckyK7Pv8xQYTw9+c+M9ybjra5/y8zvlHFOZZNRho= c=1 sm=0 a=QcIHmIcIByIA:10 a=kD9N_VxP5WMA:10 a=JC8TvPNrAAAA:8 a=F3M5lZpKAAAA:8 a=VAMm1qzQAAAA:8 a=MDZQaXdsAAAA:8 a=oCcaPWc0AAAA:8 a=jtkyqO2_Pj_cMbDYnlQA:9 a=aJmO1kg6K2ICn7V53TgA:7 a=QEXdDO2ut3YA:10 a=1PqFm7iY_d4A:10 a=wk6s2zzMB60A:10 a=nhn505YfawQA:10 a=paJYKM5s6vBnp9iG:21 a=8kg2MeDn8yn6lW_L:21 a=CeXiu7uQAAAA:8 a=3oc9M9_CAAAA:8 a=bTFp8JjJltw5KdYWrtAA:9 a=On6gCHfm_pslP_Yhp_IA:7 a=HpAAvcLHHh0Zw7uRqdWCyQ==:117 X-Spam-Score: 3.4 (+++) X-Spam-Report: autolearn=disabled,FORGED_MUA_OUTLOOK=3.36,HTML_MESSAGE=0.001 Subject: Re: LF: Ferrite RX antennas Content-Type: multipart/alternative; boundary="----=_NextPart_000_0019_01CC7EF4.CDFCF990" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: **** X-Spam-Status: No, hits=4.3 required=5.0 tests=CELL_PHONE_BOOST, FORGED_MUA_OUTLOOK,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: 1:2:496147424:93952408 X-AOL-SCOLL-URL_COUNT: 1 x-aol-sid: 3039ac1d60ca4e84d165154d 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_0019_01CC7EF4.CDFCF990 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Very good... Here I can receive with this my primitive indor ferrite rood antena (in = city) in 2004/2005: YU7AR, OK2BVG, OM2TW, S57A...Simply preamp. with = BF245. http://lea.hamradio.si/~s52ab/lf_picture/slides/indoor_fer_rood_ant_for_1= 37khz.html 73, Joze s52ab ----- Original Message -----=20 From: Stefan Sch=C3=A4fer=20 To: rsgb_lf_group@blacksheep.org=20 Sent: Thursday, September 29, 2011 9:30 PM Subject: Re: LF: Ferrite RX antennas LF, Jim, Markus, I finally finished my preamp for the /p ferrite antenna. It works = excellent and allows to stepless adjust the gain. The design is very = simple, just using a single BF862 like in my separated VLF E field = probe. Amp gain is a good 20 dB. The JFET is not directly connected to = the tuned winding (signal would be to large then with this FET) but is = decoupled with a second untuned winding of just 6 to 10 turns! I found = that this is optimal in my situation.=20 In the experimental stage i took a cardboard tube to experiment what = could be the best distance to the tuned winding but then i found that = the signal levels strongly depend on the distance of the center of the = rod. So i made the final decoupling coil movable. Now i use a PVC ring = that exactly fits on the ferrite rod's outher PVC tube (made on a = turning machine). Signal levels can be reduced by > 20 dB if the output = winding is moved to the end of the rod. This will help to prevent RX = overloading if the antenna points to DCF or DLF. So, the best S/N can = easily be obtained :-)=20 During the construction i had some trouble with oscillations of the = FET that were not so easy to avoid but later i took a longer cable (3m, = that is necessary anyway, to get some distance to the netbook) and all = works fine now! BTW i can receive DLF at 153 kHz at 40 dB S/N in 1 Hz just with that = untuned loop, i.e. 6 turns of 4 cm diameter enam. Cu wire on the FET, = without the Ferrite rod! I will further investigate about a anti-serial winding between ground = and source, to increase the antenna bandwidth... A quick circuit and picture is here: = http://dl.dropbox.com/u/19882028/LF/DK7FC_LF_p_active_ferrite_antenna.JPG= So, looking forward to new CW skeds, probably tomorrow i will go out = and try the new RX... 73, Stefan/DK7FC Am 18.08.2011 01:16, schrieb mal hamilton:=20 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 -------------------------------------------------------------------------= ----- No virus found in this message. Checked by AVG - www.avg.com Version: 10.0.1410 / Virus Database: 1520/3926 - Release Date: = 09/29/11 ------=_NextPart_000_0019_01CC7EF4.CDFCF990 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable =EF=BB=BF
Very good...
 
Here I can receive with this my = primitive indor=20 ferrite rood antena (in city) in 2004/2005: YU7AR, OK2BVG, OM2TW, = S57A...Simply=20 preamp. with BF245.
http://lea.hamradio.si/~s52ab/lf_picture/slides/indoo= r_fer_rood_ant_for_137khz.html
 
73, Joze s52ab
 
----- Original Message -----
From:=20 Stefan = Sch=C3=A4fer
Sent: Thursday, September 29, = 2011 9:30=20 PM
Subject: Re: LF: Ferrite RX=20 antennas

LF, Jim, Markus,

I finally finished my preamp = for the /p=20 ferrite antenna. It works excellent and allows to stepless adjust the = gain.=20 The design is very simple, just using a single BF862 like in my = separated VLF=20 E field probe. Amp gain is a good 20 dB. The JFET is not directly = connected to=20 the tuned winding (signal would be to large then with this FET) but is = decoupled with a second untuned winding of just 6 to 10 turns! I found = that=20 this is optimal in my situation.
In the experimental stage i took = a=20 cardboard tube to experiment what could be the best distance to the = tuned=20 winding but then i found that the signal levels strongly depend on the = distance of the center of the rod. So i made the final decoupling coil = movable. Now i use a PVC ring that exactly fits on the ferrite rod's = outher=20 PVC tube (made on a turning machine). Signal levels can be reduced by = > 20=20 dB if the output winding is moved to the end of the rod. This will = help to=20 prevent RX overloading if the antenna points to DCF or DLF. So, the = best S/N=20 can easily be obtained :-)
During the construction i had some = trouble with=20 oscillations of the FET that were not so easy to avoid but later i = took a=20 longer cable (3m, that is necessary anyway, to get some distance to = the=20 netbook) and all works fine now!

BTW i can receive DLF at 153 = kHz at 40=20 dB S/N in 1 Hz just with that untuned loop, i.e. 6 turns of 4 cm = diameter=20 enam. Cu wire on the FET, without the Ferrite rod!

I will = further=20 investigate about a anti-serial winding between ground and source, to = increase=20 the antenna bandwidth...

A quick circuit and picture is here: = http://dl.dropbox.com/u/19882028/LF/DK7FC_LF_p_active_ferrite_a= ntenna.JPG

So,=20 looking forward to new CW skeds, probably tomorrow i will go out and = try the=20 new RX...

73, Stefan/DK7FC


Am 18.08.2011 01:16, = schrieb mal=20 hamilton:=20
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=20 area.
73 es gl
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 9:30 PM Subject:=20 Re: LF: Ferrite RX antennas

Mal, LF,

Back from /p from JN49IV75OR
Mal, you are the = sceptic on=20 ferrite antennas, so pse fasten your seat belt before you take a = look on=20 this picture: http://dl.dropbox.com/u/19882028/LF/G3KEV_on_fer= rite_antenna.png

Signal=20 was audible as well: http://dl.dropbox.com/u/19882028/LF/G3KEV_audibl= e_on_ferrite_antenna.WAV
QRB=20 is 796 km.
Critical for a fast CW QSO but it is evening and QRN = was=20 high. The ferrite antenna was just 20 cm above the ground/soil and = 30m=20 RG58 in between. I used the 50 Ohm preamp during that test. =

Well=20 visible in the picture: Sferics are strongest arround 137.7, due = to the=20 high antenna Q. There was a frequency offset of about 10 Hz but = never=20 mind. Below 137.5 kHz i assume this is WSPR by PA0A?

A = comparison=20 between the 1 m diameter single turn loop was done. Both antennas = were=20 adjusted to minimise DCF39. My own test signal out of 53.8 km was = up to 55=20 dB S/N in 1 Hz on the loop without a preamp, audible of course. On = the=20 ferrite antenna + preamp it was 55 dB S/N too! But there must have = been=20 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=20 have different Q. The ferrite antenna has about twice the Q of the = loop.=20 When using the loop + preamp, the ADC gets heavyly overloaded. = Without a=20 preamp the ferrite antenna performs about 15 dB worse than the = loop. This=20 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=20 :-))

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

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

73,=20 Stefan/DK7FC



Am 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 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=20 i can receive you, i will send a capture. But i still cannot = answer.=20 Am in Darmstadt now, not in Heidelberg. The UHF link for = transmitting=20 works just in a range of 5 km and is disabled now.

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

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

73, Stefan/DK7FC

Am 17.08.2011 18:18, = schrieb mal=20 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=20 with 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=20 now.

I added a 100 pF vari-cap which allows to = resonate in=20 the desired range (up to 137.8 kHz and down to = 136.3).
As a=20 first test a added a small winding, just 3 turns, 3 cm far = for the=20 rods end, matched to 50 Ohm. So now it works as a passive = antenna=20 and can be fed to my RX 50 Ohm input.
This is the = complete LF=20 RX arrangement, 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, necessary to go on with tests on various=20 locations.

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

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

Will do = further tests=20 with a test signal in the passband and compare this to my = 1m=20 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=20 compromising SNR by connecting a low impedance=20 preamplifier. This technique has been used widely = and=20 successfully in magnetic resonance imaging ("preamp=20 decoupling"). The preamp is designed to have an = input=20 impedance that differs largely from the noise-optimum = source=20 impedance, so that you can preserve the noise match but = create=20 an 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 resonant antenna. Normally the gate input = impedance=20 (megohms) is higher than the noise optimum (tens of = kiloohms), so you would have no preamp damping at all. = The trick=20 is then to lower the input impedance by lossless = feedback,=20 which has neglegible 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=20 path. This is similar to the = old regenerative=20 audion, but with the feedback coil polarity reversed. = Another=20 configuration is parallel feedback from drain to gate, = by=20 intentionally increasing the Miller = capacitance.

Best=20 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

No virus found in = this=20 message.
Checked by AVG - www.avg.com
Version: 10.0.1410 / = Virus=20 Database: 1520/3926 - Release Date: = 09/29/11

------=_NextPart_000_0019_01CC7EF4.CDFCF990--