Return-Path: Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-dl02.r1000.mx.aol.com (Internet Inbound) with ESMTP id 6214E3800008C; Sat, 7 Jan 2012 10:43:12 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1RjYPd-0005Pq-6E for rs_out_1@blacksheep.org; Sat, 07 Jan 2012 15:42:29 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1RjYPc-0005Ph-MR for rsgb_lf_group@blacksheep.org; Sat, 07 Jan 2012 15:42:28 +0000 Received: from mail-ww0-f47.google.com ([74.125.82.47]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1RjYPa-0007le-HA for rsgb_lf_group@blacksheep.org; Sat, 07 Jan 2012 15:42:28 +0000 Received: by wgbdr12 with SMTP id dr12so280078wgb.28 for ; Sat, 07 Jan 2012 07:42:20 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; bh=xWNalZa8yw3HVKahYVVtkAxu6erS38b8atb0PY9TDDc=; b=O2j8l1JlTqM4Y9ZXrHl6WqgUtu4OEHkar2hJNiFkajXOXUKauQSIlkrs0NJSLuL8ae C6KjbxNtrIIeBdA42Gz+YPAJUy95DcHhYAmIQJf6PV2TmY72XEsBupyRAveI42nt3Est Fi7IEikdmBukMx4RO2DZOaSqz+PBuMXaADNGA= MIME-Version: 1.0 Received: by 10.180.91.42 with SMTP id cb10mr3316591wib.15.1325950939598; Sat, 07 Jan 2012 07:42:19 -0800 (PST) Received: by 10.216.164.135 with HTTP; Sat, 7 Jan 2012 07:42:19 -0800 (PST) Received: by 10.216.164.135 with HTTP; Sat, 7 Jan 2012 07:42:19 -0800 (PST) In-Reply-To: <4FB926CE6F6241D2988EE54519BDB605@JimPC> References: <001801cccd27$b3b5da80$0401a8c0@xphd97xgq27nyf> <4FB926CE6F6241D2988EE54519BDB605@JimPC> Date: Sat, 7 Jan 2012 10:42:19 -0500 Message-ID: From: "Douglas D. Williams" To: rsgb_lf_group@blacksheep.org X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: Re: LF: Re: LF Propagation Content-Type: multipart/alternative; boundary=f46d043d66fdbe8e4f04b5f202aa 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 x-aol-global-disposition: G X-AOL-SCOLL-SCORE: 0:2:503490048:93952408 X-AOL-SCOLL-URL_COUNT: 0 X-AOL-SCOLL-AUTHENTICATION: mail_rly_antispam_dkim-m225.1 ; domain : gmail.com DKIM : pass x-aol-sid: 3039ac1d4ad04f0868100725 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none --f46d043d66fdbe8e4f04b5f202aa Content-Type: text/plain; charset=ISO-8859-1 Very informative answer. Thank you. 73 de KB4OER On Jan 7, 2012 8:13 AM, "James Moritz" wrote: > Dear Doug, LF Group, > > I >> was under the (admittedly simplistic) understanding that, the lower one >> goes in frequency, the more the signal propagates via groundwave. >> > > In amateur experience, communications via ground wave up to perhaps 2000km > is feasible, so a much more significant propagation mode than at HF. The > ground wave signal strength is strongly dependent on ground conductivity, > so paths including a lot of sea water are particularly favoured. > > I do know >> that almost all military installations transmitting in the VLF/LF bands >> use >> vertical antennas (very, very large ones with huge capacity hats). >> > > Probably most amateurs are using top-loaded verticals of one sort or > another for transmit. In some circumstances, large vertical loops may be a > better option - especially in locations with many trees, where the losses > in verticals are likely to be higher. Several W & VE stations have > successfully used loops supported by trees. > > Do >> signals at 136 kHz experience "skip" from ionispheric reflection, similar >> to HF signals? >> > > Reflection takes place at much lower heights in the ionosphere at LF > frequencies, so more involving D and E layers rather than the F layers > important at HF. This results in shorter hops for sky-wave, and overlap > with ground wave coverage. So interaction between multiple modes of > propagation, with resulting QSB, can be present at any distance greater > than a few 100 kms, with some sort of propagation existing, especially > after dark, at almost any distance. > > > Alan, G3NYK has studied LF propagation in depth - see his web pages, > including at http://www.alan.melia.**btinternet.co.uk/hcf2001.htm > > Cheers, Jim Moritz > 73 de M0BMU > > --f46d043d66fdbe8e4f04b5f202aa Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable

Very informative answer. Thank you.

73 de KB4OER

On Jan 7, 2012 8:13 AM, "James Moritz"= <james.moritz@btopenwor= ld.com> wrote:
I
was under the (admittedly simplistic) understanding that, the lower one
goes in frequency, the more the signal propagates via groundwave.

In amateur experience, communications via ground wave up to perhaps 2000km = is feasible, so a much more significant propagation mode than at HF. The gr= ound wave signal strength is strongly dependent on ground conductivity, so = paths including a lot of sea water are particularly favoured.

I do know
that almost all military installations transmitting in the VLF/LF bands use=
vertical antennas (very, very large ones with huge capacity hats).

Probably most amateurs are using top-loaded verticals of one sort or anothe= r for transmit. In some circumstances, large vertical loops may be a better= option - especially in locations with many trees, where the losses in vert= icals are likely to be higher. Several W & VE stations have successfull= y used loops supported by trees.

Do
signals at 136 kHz experience "skip" from ionispheric reflection,= similar
to HF signals?

Reflection takes place at much lower heights in the ionosphere at LF freque= ncies, so more involving D and E layers rather than the F layers important = at HF. This results in shorter hops for sky-wave, and overlap with ground w= ave coverage. So interaction between multiple modes of propagation, with re= sulting QSB, can be present at any distance greater than a few 100 kms, wit= h some sort of propagation existing, especially after dark, at almost any d= istance.


Alan, G3NYK has studied LF propagation in depth - see his web pages, includ= ing at http://www.alan.melia.btinternet.co.uk/hcf2001.htm<= br>
Cheers, Jim Moritz
73 de M0BMU

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