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 w1AKVHt6004638 for ; Sat, 10 Feb 2018 21:31:20 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1ekbiR-0006tt-56 for rs_out_1@blacksheep.org; Sat, 10 Feb 2018 20:25:43 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1ekbiP-0006tk-SS for rsgb_lf_group@blacksheep.org; Sat, 10 Feb 2018 20:25:41 +0000 Received: from omr-a007e.mx.aol.com ([204.29.186.58]) by relay1.thorcom.net with esmtps (TLSv1:DHE-RSA-AES256-SHA:256) (Exim 4.89) (envelope-from ) id 1ekbiM-0006dO-J5 for rsgb_lf_group@blacksheep.org; Sat, 10 Feb 2018 20:25:40 +0000 Received: from mtaomg-aah02.mx.aol.com (mtaomg-aah02.mx.aol.com [172.27.1.144]) by omr-a007e.mx.aol.com (Outbound Mail Relay) with ESMTP id 840523800092 for ; Sat, 10 Feb 2018 15:25:35 -0500 (EST) Received: from core-acx05g.mail.aol.com (core-acx05.mail.aol.com [10.76.14.46]) by mtaomg-aah02.mx.aol.com (OMAG/Core Interface) with ESMTP id 3187238000081 for ; Sat, 10 Feb 2018 15:25:35 -0500 (EST) Received: from 188.194.222.230 by webjas-vab059.srv.aolmail.net (10.96.18.62) with HTTP (WebMailUI); Sat, 10 Feb 2018 15:25:34 -0500 Date: Sat, 10 Feb 2018 15:25:35 -0500 From: Markus Vester To: rsgb_lf_group@blacksheep.org Message-Id: <1618164fdce-c89-1c0a1@webjas-vab059.srv.aolmail.net> In-Reply-To: MIME-Version: 1.0 X-MB-Message-Source: WebUI X-MB-Message-Type: User X-Mailer: JAS STD X-Originating-IP: [188.194.222.230] x-aol-global-disposition: G DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mx.aol.com; s=20150623; t=1518294335; bh=vhZgev7NlwbWVvkydFNu1ZT7kU1CM7aTWEYfRNN8AYk=; h=From:To:Subject:Message-Id:Date:MIME-Version:Content-Type; b=mtVoLXlrzrM7gWg4I4FCgV8UnTQFuzp27bEPE8UtsjhwuW3FJGQXU6Cv8pNDkvGdg cWinxT4G/mpRqoEt3r/Ax8oYdWDOuQygDiYBrXJZwSwCNEbRSO9yxNLEcFqnfIqJci Nk2NvK9RJCCzWWOrfebJvFkylBEIi0r/Batz60t8= x-aol-sid: 3039ac1b01905a7f553f6f54 X-Spam-Score: 0.0 (/) 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 the administrator of that system for details. Content preview: Hi Clemens, David, not sure if scalar wave proponents would accept that their antenna efficiencies are restricted by the Chu-Wheeler limit... To my understanding, the reason for this fundamental Q limit is the energy stored in the 1/r^3 near field, which necessarily has to exist in the space between the outer dimensions of a small antenna and the far-field boundary lambda/2pi. The assumption is that twice per cycle, the capacitive energy of an electric antenna has to be converted to magnetic energy in the loading coil, and vice versa. The same applies for the magnetic energy of a resonanted loop antenna connected to a tuning capacitor. [...] Content analysis details: (0.0 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (markusvester[at]aol.com) -0.0 T_RP_MATCHES_RCVD Envelope sender domain matches handover relay domain 0.0 HTML_MESSAGE BODY: HTML included in message 0.0 T_DKIM_INVALID DKIM-Signature header exists but is not valid X-Scan-Signature: b707651713bcd4ad9db4bb0f5d794041 Subject: Re: VLF: 1.6 Hz from Kiruna? Content-Type: multipart/alternative; boundary="----=_Part_149860_1466426829.1518294334926" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.0 required=5.0 tests=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 ------=_Part_149860_1466426829.1518294334926 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Hi Clemens, David, not sure if scalar wave proponents would accept that their antenna efficien= cies are restricted by the Chu-Wheeler limit... To my understanding, the reason for this fundamental Q limit is the energy = stored in the 1/r^3 near field, which necessarily has to exist in the space= between the outer dimensions of a small antenna and the far-field boundary= lambda/2pi. The assumption is that twice per cycle, the capacitive energy = of an electric antenna has to be converted to magnetic energy in the loadin= g coil, and vice versa. The same applies for the magnetic energy of a reson= anted loop antenna connected to a tuning capacitor.=20 Recently someone in the LF Group mentioned a possible DARPA grant for the = development of small VLF transmitters, based on mechanical movement (vibrat= ion or rotation) of permanent magnets or polarized dielectrics. Of Course, = a rotating magnet would also need to be surrounded by same near-field energ= y as a loop (or in this case a pair of orthogonal loops for circular polari= sation). But it wouldn't necessarily need to convert the magnetic energy to= elecrtric energy. In the double-loop analogy, the magnetic energy from one= coil would be directly transferred into magnetic energy in the other coil.= So would the Chu limit still apply?=20 It seems that the only bandwidth limit would be related to the mechanical m= ass and inertia of the rotating structure, which could be made arbitrarily = small (e.g. a rotating superconducting DC coil). Or would we need to consid= er the mass of the stored energy itself, m=3DE/c^2 ?=20 Best 73, Markus (DF6NM) -----Urspr=C3=BCngliche Mitteilung-----=20 Von: Clemens Paul An: rsgb_lf_group Verschickt: Sa, 10. Feb 2018 20:43 Betreff: RE: VLF: 1.6 Hz from Kiruna? Hi David, >>Maybe you can disclose at least the the 3dB BW of this kind of antenna? >Hi Clemens, I'm not sure I understand your question. The 3 dB bandwidth is f0/Q and Q is defined as X/R where X is the reactance of the inductor and the capacitor at the resonant frequency. The lossless-Q of a small antenna is a useful academic quantity, and is the reactance divided by the radiation-resistance. It gives the maximum theoretical Q for any given small antenna, and then the actual Q can be measured on the real antenna. The radiation efficiency is the lossless Q divided by the actual Q, by the equations: Qlossless =3D X/Rrad, Qactual =3D X/(Rrad+Rloss), Qactual/Qlossless =3D Rrad/(Rrad+Rloss) =3D radiation efficiency. An interesting limit for small antennas is the minimum lossless Q that can be achieved, and was derived by Chu in 1948 from only the frequency and the size of the antenna. 73 Clemens DL4RAJ=20 >-----Original Message----- >From: owner-rsgb_lf_group@blacksheep.org=20 >[mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of David Hine >Sent: Saturday, February 10, 2018 7:13 PM >To: rsgb_lf_group@blacksheep.org >Subject: Re: VLF: 1.6 Hz from Kiruna? > ------=_Part_149860_1466426829.1518294334926 Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: quoted-printable
Hi Clemens, David,

not sure if scala= r wave proponents would accept that their antenna efficiencies are res= tricted by the Chu-Wheeler limit...

To my understanding, the reason = for this fundamental Q limit is the energy stored in the 1/r^3 ne= ar field, which necessarily has to exist in the space between the oute= r dimensions of a small antenna and the far-field boundary lambda/2pi. The = assumption is that twice per cycle, the capacitive energy of an electr= ic antenna has to be converted to magnetic energy in the loading coil, and = vice versa. The same applies for the magnetic energy of a resonanted loop a= ntenna connected to a tuning capacitor. 

Recently  so= meone in the LF Group mentioned a possible DARPA grant for the development = of small VLF transmitters, based on mechanical movement (vibration or rotat= ion) of permanent magnets or polarized dielectrics. Of Course, a rotat= ing magnet would also need to be surrounded by same near-field energy = as a loop (or in this case a pair of orthogonal loops for circular polarisa= tion). But it wouldn't necessarily need to convert the magnetic energy to e= lecrtric energy. In the double-loop analogy, the magnetic energy from one c= oil would be directly transferred into magnetic energy in the other coil.&n= bsp;So would the Chu limit still apply? 

It seems that the= only bandwidth limit would be related to the mechanical mass and inertia o= f the rotating structure, which could be made arbitrarily small (e.g. = a rotating superconducting DC coil). Or would we need to consider the mass = of the stored energy itself, m=3DE/c^2 ?

Best 73,
Markus (DF6NM)=

-----Urspr=C3=BCngliche Mitteilung-----
Von: Cleme= ns Paul <cpaul@gmx.net>
An: rsgb_lf_group <rsgb_lf= _group@blacksheep.org>
Verschickt: Sa, 10. Feb 2018 20:4= 3
Betreff: RE: VLF: 1.6 Hz from Kiruna?
Hi David,

>>Mayb= e you can disclose at least the the 3dB BW of this kind of antenna?

>Hi Clemens, I'm not sure I understand your q= uestion.

The 3 dB bandwidth is f0/Q and Q= is defined as X/R
where X is the reactance of the inductor= and the capacitor at the
resonant frequency.

The lossless-Q of a small antenna is a useful academic = quantity, and is
the reactance divided by the radiation-res= istance. It gives the maximum
theoretical Q for any given = small antenna, and then the actual Q can be
measured on the= real antenna. The radiation efficiency is the lossless Q
= divided by the actual Q, by the equations:

Qlossless =3D X/Rrad,

Qactual =3D X/(Rrad= +Rloss),

Qactual/Qlossless =3D Rrad/(Rrad+= Rloss) =3D radiation efficiency.

An intere= sting limit for small antennas is the minimum lossless Q that can
be achieved, and was derived by Chu in 1948 from only the frequency = and
the size of the antenna.

73
Clemens
DL4RAJ


>-----Original Message-----
>From: owner-rsgb_lf_group@blacksheep.org
>[mailto:owner-rsgb_lf_gro= up@blacksheep.org] On Behalf Of David Hine
>Sent: Sa= turday, February 10, 2018 7:13 PM
>To: rsgb_lf_group@blacksheep.org
>Subject: Re: VLF: 1.6 Hz from Kiruna?
>


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