Return-Path: Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by klubnl.pl (8.14.4/8.14.4/Debian-8+deb8u2) with ESMTP id w6ME1NAV027170 for ; Sun, 22 Jul 2018 16:01:26 +0200 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1fhEqc-0008D5-3A for rs_out_1@blacksheep.org; Sun, 22 Jul 2018 14:56:30 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1fhEqa-0008Cw-90 for rsgb_lf_group@blacksheep.org; Sun, 22 Jul 2018 14:56:28 +0100 Received: from smtp01.smtpout.orange.fr ([80.12.242.123] helo=smtp.smtpout.orange.fr) by relay1.thorcom.net with esmtps (TLSv1:DHE-RSA-AES256-SHA:256) (Exim 4.91_59-0488984) (envelope-from ) id 1fhEqY-0003Xm-NA for rsgb_lf_group@blacksheep.org; Sun, 22 Jul 2018 14:56:27 +0100 Received: from [192.168.1.10] ([82.126.160.254]) by mwinf5d24 with ME id DpwM1y00M5VdTVN03pwMoC; Sun, 22 Jul 2018 15:56:25 +0200 X-ME-Helo: [192.168.1.10] X-ME-Auth: ZjZjd25Ab3JhbmdlLmZy X-ME-Date: Sun, 22 Jul 2018 15:56:25 +0200 X-ME-IP: 82.126.160.254 To: rsgb_lf_group@blacksheep.org References: <164c230a3b7-c97-798@webjasstg-vaa58.srv.aolmail.net> From: F6CWN Message-ID: <926b9697-9767-b177-0aa0-c50eb785a81a@orange.fr> Date: Sun, 22 Jul 2018 13:56:22 +0000 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <164c230a3b7-c97-798@webjasstg-vaa58.srv.aolmail.net> Content-Language: fr X-Spam-Score: -0.2 (/) X-Spam-Report: Spam detection software, running on the system "relay1.thorcom.net", has NOT identified this incoming email as spam. The original message has been attached to this so you can view it or label similar future email. If you have any questions, see @@CONTACT_ADDRESS@@ for details. Content preview: What's good about Markus is that there are no limits! Untiring this OM! Thank you Markus. 73: Jeff [...] Content analysis details: (-0.2 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at http://www.dnswl.org/, no trust [80.12.242.123 listed in list.dnswl.org] -0.2 RCVD_IN_MSPIKE_H2 RBL: Average reputation (+2) [80.12.242.123 listed in wl.mailspike.net] 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (f6cwn[at]orange.fr) -0.0 T_RP_MATCHES_RCVD Envelope sender domain matches handover relay domain 0.0 HTML_MESSAGE BODY: HTML included in message X-Scan-Signature: e21031ef48bbae1c5a8c64549547751e Subject: Re: *** SPAM *** LF: Transmitting with a small ferrite antenna Content-Type: multipart/alternative; boundary="------------A33A63B197C5A9D031D07183" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.5 required=5.0 tests=HTML_20_30,HTML_MESSAGE 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 This is a multi-part message in MIME format. --------------A33A63B197C5A9D031D07183 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit What's good about Markus is that there are no limits! Untiring this OM! Thank you Markus. 73: Jeff (F6CWN) Le 22/07/2018 à 13:32, Markus Vester a écrit : > This morning I attempted to transmit from a small ferrite antenna. It > consists of a number of 9 mm diameter ferrite rods, with 7 bundled in > parallel. The bundles were stacked with overlap to ~ 35 cm total > length, and n=47 turns of litz wire were wound around the middle. > Total ferrite cross section is a=4.45 cm^2 and volume V=156 cm^3, > weighing 0.77 kg (including the coil). The coil was resonated and > matched by several 1 nF high-Q ceramic capacitors. > > Under small signal conditions (-17 dBm), the electric parameters at > 137.5 kHz were >  L = 0.50 mH, R = 0.62 ohm, Q = 690. > Applying about half a watt significantly increased inductance and > losses, and the tuning became sharply hysteretic ("jumpy"). For fine > tuning, a small rod was placed at a variable distance beside the antenna. > Then I connected my PA and drove about 25 Watts into the antenna. > Losses and inductance increased further: >  I = 1.3 A, U = 867 V (rms), L = 0.77 mH, R = 14.8 ohmn, Q = 45, > with the Q-factor now so low that tuning jumps disappeared again. The > central part under the coil became quite hot, so a tiny fan was added > which held the steady-state temperature at ~55 °C. > > From the induced voltage we can calculate the flux density in the > middle of the rod as >  B = U / n / a / omega = 48 mT (rms), > decreasing approximately linearly toward the ends (similar to a small > electric dipole). The average Bav=24 mT then results in a dipole moment of >  iA = V Bav / µ0 = 156 cm^3 * 24 mT / µ0 = 3.0 Am^2 > which results in a radiated power >  EMRP = 62.34 kohm * iA^2 / lambda^4 = 25 nW. > Thus the efficiency of this transmit antenna is only 1 ppb ! > > Anyway I attempted to detect the tiny signal on the DL0AO LF grabber, > 48 km from here: > https://lf.u01.de > Transmitting on 137.780 kHz (6:29 to 8:22 UT) indeed produced a > detectable trace in the QRSS-60 window (below the Slonim Loran line on > 137781.25 Hz). Then I attempted to send a 4-character EbNaut > transmission on 137.510 KHz, which was successfully decoded with some > margin. > > Now if that's not QRP... anyway fascinating, considering that the > small ferrite antenna might be carried in a handbag, buried in the > ground or taken to a cave. > > Best 73, > Markus (DF6NM) > --------------A33A63B197C5A9D031D07183 Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: 8bit

What's good about Markus is that there are no limits!
Untiring this OM!

Thank you Markus.

73: Jeff

(F6CWN)


Le 22/07/2018 à 13:32, Markus Vester a écrit :
This morning I attempted to transmit from a small ferrite antenna. It consists of a number of 9 mm diameter ferrite rods, with 7 bundled in parallel. The bundles were stacked with overlap to ~ 35 cm total length, and n=47 turns of litz wire were wound around the middle. Total ferrite cross section is a=4.45 cm^2 and volume V=156 cm^3, weighing 0.77 kg (including the coil). The coil was resonated and matched by several 1 nF high-Q ceramic capacitors.

Under small signal conditions (-17 dBm), the electric parameters at 137.5 kHz were
 L = 0.50 mH, R = 0.62 ohm, Q = 690.
Applying about half a watt significantly increased inductance and losses, and the tuning became sharply hysteretic ("jumpy"). For fine tuning, a small rod was placed at a variable distance beside the antenna.
Then I connected my PA and drove about 25 Watts into the antenna. Losses and inductance increased further:
 I = 1.3 A, U = 867 V (rms), L = 0.77 mH, R = 14.8 ohmn, Q = 45,
with the Q-factor now so low that tuning jumps disappeared again. The central part under the coil became quite hot, so a tiny fan was added which held the steady-state temperature at ~55 °C.

From the induced voltage we can calculate the flux density in the middle of the rod as
 B = U / n / a / omega = 48 mT (rms),
decreasing approximately linearly toward the ends (similar to a small electric dipole). The average Bav=24 mT then results in a dipole moment of
 iA = V Bav / µ0 = 156 cm^3 * 24 mT / µ0 = 3.0 Am^2
which results in a radiated power
 EMRP = 62.34 kohm * iA^2 / lambda^4 = 25 nW.
Thus the efficiency of this transmit antenna is only 1 ppb !

Anyway I attempted to detect the tiny signal on the DL0AO LF grabber, 48 km from here:
https://lf.u01.de
Transmitting on 137.780 kHz (6:29 to 8:22 UT) indeed produced a detectable trace in the QRSS-60 window (below the Slonim Loran line on 137781.25 Hz). Then I attempted to send a 4-character EbNaut transmission on 137.510 KHz, which was successfully decoded with some margin.

Now if that's not QRP... anyway fascinating, considering that the small ferrite antenna might be carried in a handbag, buried in the ground or taken to a cave.

Best 73,
Markus (DF6NM)


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