X-GM-THRID: 1198230260675793125 X-Gmail-Labels: rsgb lf X-Gmail-Received: 26091bc9d83c375a4081270ffee05f5175325339 Delivered-To: daveyxm@gmail.com Received: by 10.54.70.14 with SMTP id s14cs20463wra; Sun, 19 Mar 2006 04:13:04 -0800 (PST) Received: by 10.65.75.19 with SMTP id c19mr464710qbl; Sun, 19 Mar 2006 04:13:04 -0800 (PST) Return-Path: Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mx.gmail.com with ESMTP id d5si3423735qbd.2006.03.19.04.13.02; Sun, 19 Mar 2006 04:13:04 -0800 (PST) Received-SPF: neutral (gmail.com: 193.82.116.20 is neither permitted nor denied by best guess record for domain of owner-rsgb_lf_group@blacksheep.org) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1FKwkN-0005BV-Uy for rs_out_1@blacksheep.org; Sun, 19 Mar 2006 12:10:59 +0000 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1FKwkN-0005BM-9x for rsgb_lf_group@blacksheep.org; Sun, 19 Mar 2006 12:10:59 +0000 Received: from smtp807.mail.ukl.yahoo.com ([217.12.12.197]) by relay1.thorcom.net with smtp (Exim 4.51) id 1FKyLB-0006ea-Im for rsgb_lf_group@blacksheep.org; Sun, 19 Mar 2006 13:53:21 +0000 Received: (qmail 92259 invoked from network); 19 Mar 2006 12:10:37 -0000 Received: from unknown (HELO ?213.122.60.2?) (james.moritz@btopenworld.com@213.122.60.2 with login) by smtp807.mail.ukl.yahoo.com with SMTP; 19 Mar 2006 12:10:36 -0000 Received: from 127.0.0.1 (AVG SMTP 7.1.385 [268.2.5/284]); Sun, 19 Mar 2006 12:09:17 +0000 Message-ID: <001f01c64b4d$f258aae0$023c7ad5@w4o8m9> From: "James Moritz" To: References: <000901c64aab$8824e460$1ce4fc3e@your4105e587b6> <002101c64adb$e5924720$6211f4cc@p1i5f0> <007401c64aeb$4b30d7e0$0600000a@quaycustomer> Date: Sun, 19 Mar 2006 12:09:17 -0000 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 5.00.2615.200 X-MimeOLE: Produced By Microsoft MimeOLE V5.00.2615.200 X-Spam-Score: -1.0 (-) X-Spam-Report: autolearn=disabled,AWL=-1.542,HTML_20_30=0.504,HTML_MESSAGE=0.001 Subject: LF: Re: LOOPS V VERTICALS Content-Type: multipart/alternative; boundary="----=_NextPart_000_001C_01C64B4D.F2265040" 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 Status: O X-Status: X-Keywords: X-UID: 5984 This is a multi-part message in MIME format. ------=_NextPart_000_001C_01C64B4D.F2265040 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Dear LF Group, At M0BMU, the original motivation for using seperate RX antennas was the = increasing 50Hz-related noise level on the TX vertical. This seems to be = due to pick-up from the house mains wiring, but moving the vertical = further from the house would result in reduced possible length, and it = is short enough already! Remote vertical antennas worked fine as far as eliminating mains noise = was concerned, but did nothing to reduce distant sources of QRM such as = Loran. Here I have to use quite selective antennas (the broadband = active-whip type of antenna is not really workable here due to the 20V/m = MF signal levels from Brookmans Park). For some time I used single loops = oriented to null out the Lessay Loran signal, and I estimated this = reduced the noise floor for most European signals by 6dB or so, which = made quite a few more stations audible. I found that much = experimentation was needed to find suitable positions for the loops = where they would null out Loran, but not pick up 50Hz noise at the same = time - loops seem to be more sensitive to this type of QRM. Then the Rugby Loran started up, and the band noise level in aural = reception bandwidths (e.g. 300Hz) increased by 15dB, wiping out many of = the weaker signals at this QTH. I countered this using both loop and = vertical antennas phased together to provide two adjustable nulls aimed = at Rugby and Lessay. This brought the situation for aural reception of = European sigs to about the same place as it was before - but most = signals coming from the west are attenuated by the overall directional = properties of the system. So, for aural signal reception at this location in SE England, currently = neither loops nor vertical antennas by themselves work very well, = allthough quite good results are achieved by using a phasing system with = both types of antenna to null out the Loran.=20 For narrow-band QRSS, etc. signals, the situation is different, since = provided the received signal frequency does not coincide with a Loran = line, Loran does not matter too much. There does not seem to be much to = choose between the loop and the vertical most of the time, however under = quiet band conditions with little QRN I have found that if I use the = phased loop and vertical antennas, and reverse the relative phase of the = antennas to favour signals from the west (i.e. for transatlantic = reception), the band noise is reduced by several dB on the spectrogram = compared to either antenna by itself - I suspect this may be due to a = reduction in "Luxembourg effect" noise originating from Europe to the = east. So here I find it neccessary to use both types of antenna = simultaneously, if I want to achieve good results. This is mostly to = overcome the effects of man-made QRM and to enable aural reception of = signals, which are perhaps the main differences between my situation and = the others who have commented.=20 Cheers, Jim Moritz 73 de M0BMU ------=_NextPart_000_001C_01C64B4D.F2265040 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Dear LF Group,
 
At M0BMU, the original motivation for = using=20 seperate RX antennas was the increasing 50Hz-related noise level on = the TX=20 vertical. This seems to be due to pick-up from the house mains wiring, = but=20 moving the vertical further from the house would result in reduced = possible=20 length, and it is short enough already!
 
Remote vertical antennas = worked fine as far as=20 eliminating mains noise was concerned, but did nothing to reduce = distant=20 sources of QRM such as Loran. Here I have to use quite selective = antennas (the=20 broadband active-whip type of antenna is not really workable here due to = the=20 20V/m MF signal levels from Brookmans Park). For some time I used single = loops=20 oriented to null out the Lessay Loran signal, and I estimated this = reduced=20 the noise floor for most European signals by 6dB or so, which made quite = a few=20 more stations audible. I found that much experimentation was needed to = find=20 suitable positions for the loops where they would null out Loran, but = not pick=20 up 50Hz noise at the same time - loops seem to be more sensitive to this = type of=20 QRM.
 
Then the Rugby Loran started up, and = the band noise=20 level in aural reception bandwidths (e.g. 300Hz) increased by 15dB, = wiping=20 out many of the weaker signals at this QTH. I countered this=20 using both loop and vertical antennas phased together to provide = two=20 adjustable nulls aimed at Rugby and Lessay. This brought the situation = for aural=20 reception of European sigs to about the same place as it was before - = but most=20 signals coming from the west are attenuated by the overall directional=20 properties of the system.
 
So, for aural=20 signal reception at this location in SE England, currently neither  = loops=20 nor vertical antennas by themselves work very well, allthough quite good = results=20 are achieved by using a phasing system with both types of antenna to = null out=20 the Loran.
 
For narrow-band QRSS, etc. signals, the = situation=20 is different, since provided the received signal frequency does not = coincide=20 with a Loran line, Loran does not matter too much. There does not seem = to be=20 much to choose between the loop and the vertical most of the time, = however under=20 quiet band conditions with little QRN I have found that if I use the = phased loop=20 and vertical antennas, and reverse the relative phase of the antennas to = favour=20 signals from the west (i.e. for transatlantic reception), the band noise = is=20 reduced by several dB on the spectrogram compared to either = antenna by=20 itself - I suspect this may be due to a reduction in "Luxembourg effect" = noise=20 originating from Europe to the east.
 
So here I find it neccessary to = use both types=20 of antenna simultaneously, if I want to achieve good results. This is = mostly to=20 overcome the effects of man-made QRM and to enable aural reception of = signals,=20 which are perhaps the main differences between my situation and the = others who=20 have commented.
 
Cheers, Jim Moritz
73 de M0BMU
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