Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-mb01.r1000.mx.aol.com (Internet Inbound) with ESMTP id 380E738000081; Fri, 30 Sep 2011 06:14:58 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1R9a5v-0006Fm-6V for rs_out_1@blacksheep.org; Fri, 30 Sep 2011 11:13:27 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1R9a5t-0006Fd-Vo for rsgb_lf_group@blacksheep.org; Fri, 30 Sep 2011 11:13:25 +0100 Received: from out1.ip03ir2.opaltelecom.net ([62.24.128.239]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1R9a5p-0004ZT-4c for rsgb_lf_group@blacksheep.org; Fri, 30 Sep 2011 11:13:25 +0100 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: Aq8AAO+UhU5Ok8e6/2dsb2JhbABBgk2CGJQ1jw6BBoFOBQEBBQgBAQMWCikCEwEIAg4BAQMFAgEDEQQBAQoXCgICFAEEGgYWCAYTCgECAgEBh2wEpVeRYYYNgRMEglSiRQ X-IronPort-AV: E=Sophos;i="4.68,466,1312153200"; d="scan'208,217";a="361663475" Received: from host-78-147-199-186.as13285.net (HELO xphd97xgq27nyf) ([78.147.199.186]) by out1.ip03ir2.opaltelecom.net with SMTP; 30 Sep 2011 11:13:14 +0100 Message-ID: <000e01cc7f59$8fcc9cb0$0401a8c0@xphd97xgq27nyf> From: "mal hamilton" 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: Fri, 30 Sep 2011 10:13:12 -0000 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_000B_01CC7F59.8F850C60" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: ** X-Spam-Status: No, hits=2.7 required=5.0 tests=CELL_PHONE_BOOST,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: 1:2:493650496:93952408 X-AOL-SCOLL-URL_COUNT: 1 x-aol-sid: 3039ac1d60154e8596a27bdf 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_000B_01CC7F59.8F850C60 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Stefan es Co Wind an AIR coil with the same inductance as your ferrite coil and = compare the difference. It might be slightly larger and slightly more = wire resistance but I think the performance will be the same maybe = better especially if the coil is encased in a helium tube. I am thinking back to my /Mobile days and loading coils which worked FB = both on TX and RX and on MF ie 160 metres. Some commercial produced coils encased in helium tubes had vy high Q = that would rival the ferrite variety used today. even non helium types were manufactured to a high standard with hi Q There is nothing new. It is just re inventing the wheel with a few = modern day tweaks mal/g3kev ----- Original Message -----=20 From: Stefan Sch=C3=A4fer=20 To: rsgb_lf_group@blacksheep.org=20 Sent: Thursday, September 29, 2011 7:30 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 ------=_NextPart_000_000B_01CC7F59.8F850C60 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable =EF=BB=BF
Stefan es Co
Wind an AIR coil with the same inductance as = your ferrite=20 coil and compare the difference. It might be slightly larger and = slightly more=20 wire resistance but I think the performance will be the same maybe = better=20 especially if the coil is encased in a helium tube.
I am thinking back to my /Mobile days and = loading coils=20 which worked FB both on TX and RX and on MF ie 160 metres.
Some commercial produced coils encased in helium = tubes had=20 vy high Q that would rival the ferrite variety used today.
even non helium types were manufactured to a = high standard=20 with hi Q
There is nothing new. It is just re inventing = the wheel=20 with a few modern day tweaks
mal/g3kev
 
----- Original Message -----
From:=20 Stefan = Sch=C3=A4fer
Sent: Thursday, September 29, = 2011 7:30=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
------=_NextPart_000_000B_01CC7F59.8F850C60--