X-GM-THRID: 1198857620180555603 X-Gmail-Labels: rsgb lf X-Gmail-Received: b72e11e26633bf68013bded8968c66fba1f4f75d Delivered-To: daveyxm@gmail.com Received: by 10.54.127.8 with SMTP id z8cs13818wrc; Sat, 25 Mar 2006 12:48:41 -0800 (PST) Received: by 10.65.183.14 with SMTP id k14mr359192qbp; Sat, 25 Mar 2006 12:48:41 -0800 (PST) Return-Path: Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mx.gmail.com with ESMTP id f17si1746794qba.2006.03.25.12.48.39; Sat, 25 Mar 2006 12:48:41 -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 1FNFe5-0005Jz-FX for rs_out_1@blacksheep.org; Sat, 25 Mar 2006 20:46:01 +0000 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1FNFe4-0005Jq-T1 for rsgb_lf_group@blacksheep.org; Sat, 25 Mar 2006 20:46:00 +0000 Received: from smtp802.mail.ukl.yahoo.com ([217.12.12.139]) by relay1.thorcom.net with smtp (Exim 4.51) id 1FNHHD-0003cf-Ro for rsgb_lf_group@blacksheep.org; Sat, 25 Mar 2006 22:30:51 +0000 Received: (qmail 1500 invoked from network); 25 Mar 2006 20:45:40 -0000 Received: from unknown (HELO aquarids) (ganymede444@btinternet.com@86.134.204.52 with login) by smtp802.mail.ukl.yahoo.com with SMTP; 25 Mar 2006 20:45:40 -0000 From: "Dave G3WCB" To: Date: Sat, 25 Mar 2006 20:46:57 -0000 Message-ID: MIME-Version: 1.0 X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook IMO, Build 9.0.2416 (9.0.2911.0) In-Reply-To: <006b01c65030$fb621800$0b01a8c0@server> X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1441 Importance: Normal X-Spam-Score: -0.7 (/) X-Spam-Report: autolearn=disabled,AWL=-1.334,FROM_ENDS_IN_NUMS=0.516,HTML_50_60=0.095,HTML_MESSAGE=0.001 Subject: LF: RE: Answers to antenna question Content-Type: multipart/alternative; boundary="----=_NextPart_000_000C_01C6504D.41BA9A90" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: * X-Spam-Status: No, hits=1.8 required=5.0 tests=FROM_ENDS_IN_NUMS,HTML_30_40, HTML_FONTCOLOR_BLUE,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: 6141 This is a multi-part message in MIME format. ------=_NextPart_000_000C_01C6504D.41BA9A90 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Hi, JB, LF, Try and keep the top loading wires at least 4-6 feet away from the support towers, and make sure that the wires are taut and don't sway about in the breeze. You will find that the antenna is sharply tuned, and the tuning will vary as the wind blows! This also applies to bits of the antenna that you would think would be at the same potential, e.g. parellel multiple wire feed lines. If you want to increase the top-loading capacity...always a good thing... you can join the ends of the "legs" of the Y with further wires. This will allow you to reduce the size of the tuning coil and reduce your losses. If you do intend to transmit with this antenna, pay attention to the way you terminate the ends of the top wires. Try to avoid sharp points, and end the wires in loops to reduce corona effects. I get significant corona running 200W RF into a Tee with a 60m top, and it only gets worse as you turn up the wick. This can cause TVI...well it does for me! Lastly, if you are using a tuned loop nearby to receive, you will find that the vertical will play havoc with the polar diagram of the loop if it is tuned to the same frequency. I get round this by using a relay to open the earthy end of the coil when the vertical isn't in use. I'm not sure what the VE licensing regulations allow, but it can be fun to just put a couple of watts of RF into the antenna, to see how the whole thing tunes up. You don't need much, just 4 or 5 watts from an "audio" amp on 137 kHz is all you need. I can recommend Jim M0BMU's phase meter as a really useful means of detecting if your antenna is on tune, and you can watch the phase swing around when the wind blows! http://www.picks.plus.com/software/LFtunemeter.pdf 73, Dave G3WCB IO91RM -----Original Message----- From: owner-rsgb_lf_group@blacksheep.org [mailto:owner-rsgb_lf_group@blacksheep.org]On Behalf Of J. B. Weazle McCreath Sent: 25 March 2006 17:24 To: rsgb_lf_group@blacksheep.org Cc: lowfer@lwca.org Subject: LF: Answers to antenna question Hello Alan, Jay, Warren, et all, Thanks for your replies to my question concerning a "T" antenna. As you had suggested, I plan to use Dacron rope between the end insulators and the towers. The insulators are commercial ones that I "liberated" from a ship's HF antenna, so they should be fine for my application. I do intend to transmit at some time in the future, but for now the antenna will be used for receiving. The top loading will be three wires, one from each of the towers, converging at a common point midway between them, which by luck is also over a naturally wet area of my property. There will be a total length of 190 feet of horizontal top loading, the ends being slightly higher than the central common point. I plan on using a multiple rod grounding system at the feed point, along with tieing into the # 8 bonding ground wires interconnecting the three towers. Those bonding wires also connect to the mains grounds at both my house and the shop, about 100 feet apart, so I'm confident that I've got a pretty good ground system. 73, J.B., VE3EAR - VE3WZL Solar and wind powered EN93dr ------=_NextPart_000_000C_01C6504D.41BA9A90 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Hi,=20 JB, LF,
 
Try=20 and keep the top loading wires at least 4-6 feet away from the support = towers,=20 and make sure that the wires are taut and don't sway about in the = breeze. You=20 will find that the antenna is sharply tuned, and the tuning will vary as = the=20 wind blows! This also applies to bits of the antenna that you would = think would=20 be at the same potential, e.g. parellel multiple wire feed=20 lines.
 
If you=20 want to increase the top-loading capacity...always a good thing... you = can join=20 the ends of the "legs" of the Y with further wires. This will allow you = to=20 reduce the size of the tuning coil and reduce your losses.=20
 
If you=20 do intend to transmit with this antenna, pay attention to the way you = terminate=20 the ends of the top wires. Try to avoid sharp points, and end the wires = in loops=20 to reduce corona effects. I get significant corona running 200W RF into = a Tee=20 with a 60m top, and it only gets worse as you turn up the wick. This can = cause=20 TVI...well it does for me! 
 
Lastly, if you are using a tuned loop nearby to receive, you = will find=20 that the vertical will play havoc with the polar diagram of the = loop if it=20 is tuned to the same frequency. I get round this by using a relay to = open the=20 earthy end of the coil when the vertical isn't in = use.
 
I'm=20 not sure what the VE licensing regulations allow, but it can be fun to = just put=20 a couple of watts of RF into the antenna, to see how the whole thing = tunes up.=20 You don't need much, just 4 or 5 watts from an "audio" amp on 137 kHz is = all you=20 need. I can recommend Jim M0BMU's phase meter as a really useful means = of=20 detecting if your antenna is on tune, and you can watch the phase = swing=20 around when the wind blows!
 
http://www.pi= cks.plus.com/software/LFtunemeter.pdf
 
73,=20 Dave G3WCB IO91RM 
 
-----Original Message-----
From:=20 owner-rsgb_lf_group@blacksheep.org=20 [mailto:owner-rsgb_lf_group@blacksheep.org]On Behalf Of J. B. = Weazle=20 McCreath
Sent: 25 March 2006 17:24
To:=20 rsgb_lf_group@blacksheep.org
Cc: = lowfer@lwca.org
Subject:=20 LF: Answers to antenna question

Hello Alan, Jay, Warren, et = all,
 
Thanks for your replies to my = question concerning=20 a "T" antenna.
As you had suggested, I plan to use = Dacron rope=20 between the
end insulators and the towers.  = The=20 insulators are commercial
ones that I "liberated" from a = ship's HF antenna, so they should
be fine for my application.  I = do intend to=20 transmit at some time
in the future, but for now the = antenna=20 will be used for receiving.
 
The top loading will be three wires, = one from=20 each of the towers,
converging at a common point midway = between them,=20 which by
luck is also over a = naturally wet area=20 of my property.  There will
be a total length of 190 feet of = horizontal top=20 loading, the ends
being slightly higher than the = central common=20 point.
 
I plan on using a multiple rod grounding system at the feed point,
along with tieing into the # 8 bonding ground wires=20 interconnecting
the three towers.  Those bonding = wires also=20 connect to the mains
grounds at both my house and the = shop, about 100=20 feet apart, so
I'm confident that I've got a pretty = good ground=20 system.
 
73, J.B., VE3EAR - VE3WZL
Solar = and wind=20 powered
EN93dr
 
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