Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on lipkowski.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=5.0 tests=FREEMAIL_FORGED_FROMDOMAIN, FREEMAIL_FROM,HEADER_FROM_DIFFERENT_DOMAINS,HTML_MESSAGE,RCVD_IN_DNSWL_MED, SPF_PASS,T_DKIM_INVALID autolearn=ham autolearn_force=no version=3.4.0 X-Spam-DCC: INFN-TO: mailn 1233; Body=2 Fuz1=2 Fuz2=2 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by lipkowski.org (8.14.4/8.14.4/Debian-8+deb8u1) with ESMTP id v0O7teKW012293 for ; Tue, 24 Jan 2017 08:55:41 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1cVvoV-0006qg-IR for rs_out_1@blacksheep.org; Tue, 24 Jan 2017 07:46:47 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1cVvoU-0006qX-FT for rsgb_lf_group@blacksheep.org; Tue, 24 Jan 2017 07:46:46 +0000 Received: from resqmta-ch2-01v.sys.comcast.net ([2001:558:fe21:29:69:252:207:33]) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.87) (envelope-from ) id 1cVvoQ-0005z5-Aa for rsgb_lf_group@blacksheep.org; Tue, 24 Jan 2017 07:46:45 +0000 Received: from resomta-ch2-06v.sys.comcast.net ([69.252.207.102]) by resqmta-ch2-01v.sys.comcast.net with SMTP id VvoMcmX5gRNZDVvoMcwnBB; Tue, 24 Jan 2017 07:46:38 +0000 X-DKIM-Result: Domain=comcast.net Result=Signature OK DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=comcast.net; s=q20161114; t=1485243998; bh=fxM+i6ILigF1F25menIfO583mlEvOj0eZqPoVufX94A=; h=Received:Received:From:To:Subject:Date:Message-ID:MIME-Version: Content-Type; b=bKzqRlsyOIwNovLVuxEaU/E2tfg28EKcgvcY7MCMiV+SjdL7z2ixjptGEUujtvDuO BLu6cUELwSJ5n6K8uoOK638hlXD4aDg53WixvyMQGByO0T/EHRm0LELX1oPfv7ys57 6N9hrYAonRy2N23O5cDeRExDPo1JvekUrwF1TtgnORQHiTIKQOFrC933avoRVOZz74 Tco1sRRd9uKAeEi6pBbP1nnQFvvCrjhG0sp7KUUX08gFcGv+1EIODiRkY7f+NyEvoX zf8uBE0552WTDo59t0/dp620823UNC+AAVtACnvudPcpvGSsN1qdKAKRzJ6WgDwiml 4kF5uYIx/hMkw== Received: from Owner ([166.171.59.22]) by resomta-ch2-06v.sys.comcast.net with SMTP id VvmFcmG6o1ow6VvmJckCB3; Tue, 24 Jan 2017 07:44:36 +0000 From: To: References: <159cd6620ca-6fdd-1526c@webprd-a74.mail.aol.com> In-Reply-To: <159cd6620ca-6fdd-1526c@webprd-a74.mail.aol.com> Date: Tue, 24 Jan 2017 02:44:24 -0500 Message-ID: <025401d27615$b3bd3cc0$1b37b640$@comcast.net> MIME-Version: 1.0 X-Mailer: Microsoft Outlook 14.0 Thread-Index: AQJDWboY480Pw0TN0uB6InkXDkMzdaBlWPxQ Content-Language: en-us X-CMAE-Envelope: MS4wfKUyTxgVVWEyBzJuWcr3C8Ia6i64SZsA/ImueAR6jUUHkWFQxE4IZo0ylBs0KhAyoy5ubDGPzj8546p3tdTSvpp83ZFdJ65F0jZDzbJZNO1qUGNkSbCl zAsiyokRtWe8Y0ILLIDMDy7H+98xg8A7gERFVgsAZHqr5Z3zD3pAPceo X-Scan-Signature: 9c6f861813be21b949fefb381c49ca48 Subject: LF: RE: Three dots Content-Type: multipart/alternative; boundary="----=_NextPart_000_0255_01D275EB.CAE9A5C0" 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-Scanned-By: MIMEDefang 2.75 Status: RO X-Status: X-Keywords: X-UID: 10320 This is a multipart message in MIME format. ------=_NextPart_000_0255_01D275EB.CAE9A5C0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Markus, =20 Very interesting observations. I had been wondering about the = orientation of the loop vs incident wave polarization for three reasons: 1) Changes in wave polarization from near field to far field: with a = small loop TX antenna the magnetic field polarization changes from near = field to far field in a manner that is consistent with your RX-antenna = orientation example, but I confirmed via NEC 6+ with a realistic ground = that this is not the case with the magnetic components from small = horizontal or vertical monopoles/dipoles. I=E2=80=99m guessing that you = and others already knew this but I didn=E2=80=99t have a strong = intuition about the magnetic near field of a short monopole especially = if inclined from vertical, so I simulated. Item (1) seems irrelevant = based on the simulation. 2) Mixed skywave/groundwave polarization variation: I ran some = simulations with fairly reasonable 10-minute updates to h=E2=80=99 and = beta, showing ~ 60 degree daily phase variability at 3kHz / 170km, = mostly from 1st and 2nd hop mixing with groundwave (almost 1:1 ratio). = The simulated diurnal phase signature was not nearly as distinct and = simple in the 2970 Hz 170 km case as in a 20 kHz 2000 km case; the (2970 = Hz 170 km) results show phase changing constantly i.e. no distinct = stable time of the type seen at 20kHz 2000 km; and the results show = phase fairly sensitive to ionospheric variations (h=E2=80=99 and beta). = These characteristics are perhaps qualitatively and perhaps even = quantitatively reminiscent of the color changes in Stefan=E2=80=99s = color-DF grabber, but I did not think of that particular association = until I read your message below; thank you for that valuable = observation. One big caveat: I am not confident about the fidelity of = the simulations at 2970 Hz; I think that the models are poorly validated = between 2kHz and 4kHz (i.e. at/near modal cutoff and attenuation peak). 3) Mixed skywave/groundwave polarization bias: based on the above, it = seems unlikely that the skywave would be near-vertically polarized at = such a steep angle and at such a short distance from the polarizing = reflection; and with skywave/groundwave ratio ~ 1:1 at 2970 Hz 170km, it = seems reasonable that the projection of the non-vertical vector onto the = sensitive plane of the loop would be significant. Even a 20 degree angle = from vertical could project up to almost 34% of the field onto the = sensitive plane of the loop (does this seem reasonable to you?) I have = seen substantially non-vertical skywaves at VLF on many occasions, and = have been uncertain about fixed-orientation RX loops for that reason (a = compact 3-axis ferrite antenna would dispense with that uncertainty but = ferrite has its own issues). I usually angulate single axis loops in = both axes for best signal, but I am often portable near infrastructure = so in many cases I don=E2=80=99t know if the unusual polarizations are = due to infrastructure or due to polarization preserved from a high-angle = and therefore also short range polarized reflection. But in many cases = it has been possible to confirm unexpected polarization due to modal = mixing with skywaves. =20 Best, =20 Jim AA5BW =20 =20 =20 From: owner-rsgb_lf_group@blacksheep.org = [mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of Markus Vester Sent: Monday, January 23, 2017 5:16 PM To: rsgb_lf_group@blacksheep.org Subject: VLF: Three dots =20 Interestingly, my on 8270.0025 Hz carrier transmissions during the last = three evenings Jan 20, 18:00 - 23:00 UT, Jan 21, 15:28 - 23:00 UT, Jan 22, 13:23 - 23:00 UT left three dots on Stefan's 47 uHz spectrogram = http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber2.html . This is astonishing because the tree-receiver is currently connected to = a north-south oriented loop, whereas I am due east in a null. So I was = wondering whether reception was made possible by skywave with rotated = polarisation? Perhaps reminiscent of the playful colour changes on = Stefan's MF colour-DF grabber. Despite much lower noise background, the (shorter) daytime carrier Jan 22, 07:00 - 10:00 UT. left no trace at all. Best 73, Markus (DF6NM) ------=_NextPart_000_0255_01D275EB.CAE9A5C0 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable

Markus,

 

Very interesting observations. I had been wondering about the = orientation of the loop vs incident wave polarization for three = reasons:

1) Changes in wave polarization from near field to far field: with a = small loop TX antenna the magnetic field polarization changes from near = field to far field in a manner that is consistent with your RX-antenna = orientation example, but I confirmed via NEC 6+ with a realistic ground = that this is not the case with the magnetic components from small = horizontal or vertical monopoles/dipoles. I=E2=80=99m guessing that you = and others already knew this but I didn=E2=80=99t have a strong = intuition about the magnetic near field of a short monopole especially = if inclined from vertical, so I simulated. Item (1) seems irrelevant = based on the simulation.

2) Mixed skywave/groundwave polarization variation: I ran some = simulations with fairly reasonable 10-minute updates to h=E2=80=99 and = beta, showing ~ 60 degree daily phase variability at 3kHz / 170km, = mostly from 1st and 2nd hop mixing with groundwave (almost 1:1 ratio). = The simulated diurnal phase signature was not nearly as distinct and = simple in the 2970 Hz 170 km case as in a 20 kHz 2000 km case; the (2970 = Hz 170 km) results show phase changing constantly i.e. no distinct = stable time of the type seen at 20kHz 2000 km; and the results show = phase fairly sensitive to ionospheric variations (h=E2=80=99 and beta). = These characteristics are perhaps qualitatively and perhaps even = quantitatively reminiscent of the color changes in Stefan=E2=80=99s = color-DF grabber, but I did not think of that particular association = until I read your message below; thank you for that valuable = observation. One big caveat: I am not confident about=C2=A0 the fidelity = of the simulations at 2970 Hz; I think that the models are poorly = validated between 2kHz and 4kHz (i.e. at/near modal cutoff and = attenuation peak).

3) Mixed skywave/groundwave polarization bias: =C2=A0based on the = above, it seems unlikely that the skywave would be near-vertically = polarized at such a steep angle and at such a short distance from the = polarizing reflection; and with skywave/groundwave ratio ~ 1:1 at 2970 = Hz 170km, it seems reasonable that the projection of the non-vertical = vector onto the sensitive plane of the loop would be significant. Even a = 20 degree angle from vertical could project up to almost 34% of the = field onto the sensitive plane of the loop (does this seem reasonable to = you?) I have seen substantially non-vertical skywaves at VLF on many = occasions, and have been uncertain about fixed-orientation RX loops for = that reason (a compact 3-axis ferrite antenna would dispense with that = uncertainty but ferrite has its own issues). I usually angulate single = axis loops in both axes for best signal, but I am often portable near = infrastructure so in many cases I don=E2=80=99t know if the unusual = polarizations are due to infrastructure or due to polarization preserved = from a high-angle and therefore also short range polarized reflection. = But in many cases it has been possible to confirm unexpected = polarization due to modal mixing with skywaves.

 

Best,

 

Jim AA5BW =C2=A0

=C2=A0=C2=A0=C2=A0=C2=A0

 

From:= = owner-rsgb_lf_group@blacksheep.org = [mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of Markus = Vester
Sent: Monday, January 23, 2017 5:16 PM
To: = rsgb_lf_group@blacksheep.org
Subject: VLF: Three = dots

 

I= nterestingly, my on 8270.0025 Hz carrier transmissions during the = last three evenings
 Jan 20, 18:00 - 23:00 UT,
 Jan 21, = 15:28 - 23:00 UT,
 Jan 22, 13:23 - 23:00 UT
left three dots = on Stefan's 47 uHz spectrogram http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber2.ht= ml .

This is astonishing because the tree-receiver is = currently connected to a north-south oriented loop, whereas I = am due east in a null. So I was wondering = whether reception was made possible by skywave with rotated = polarisation? Perhaps reminiscent of the playful = colour changes on Stefan's MF colour-DF = grabber.

Despite much lower noise background, the (shorter) = daytime carrier
 Jan 22, 07:00 - 10:00 UT.
left no trace at = all.

Best 73,
Markus = (DF6NM)

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