X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Sun, 03 Feb 2008 21:11:04 -0500 Message-ID: X-Original-Return-Path: Received: from vms044pub.verizon.net ([206.46.252.44] verified) by logan.com (CommuniGate Pro SMTP 5.2.0) with ESMTP id 2713540 for lml@lancaironline.net; Sun, 03 Feb 2008 13:18:21 -0500 Received-SPF: pass receiver=logan.com; client-ip=206.46.252.44; envelope-from=tom.gourley@verizon.net Received: from jacky0da39824a ([71.111.134.35]) by vms044.mailsrvcs.net (Sun Java System Messaging Server 6.2-6.01 (built Apr 3 2006)) with ESMTPA id <0JVO00424DH7U8L3@vms044.mailsrvcs.net> for lml@lancaironline.net; Sun, 03 Feb 2008 12:17:35 -0600 (CST) X-Original-Date: Sun, 03 Feb 2008 10:17:29 -0800 From: "Tom Gourley" Subject: Re: [LML] Curious radioproblems X-Original-To: "Lancair Mailing List" Reply-to: "Tom Gourley" X-Original-Message-id: <005201c86691$0a7d6420$660610ac@jacky0da39824a> MIME-version: 1.0 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2900.3198 X-Mailer: Microsoft Outlook Express 6.00.2900.3138 Content-type: multipart/alternative; boundary="----=_NextPart_000_004F_01C8664D.FB708770" X-Priority: 3 X-MSMail-priority: Normal References: This is a multi-part message in MIME format. ------=_NextPart_000_004F_01C8664D.FB708770 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MessageChrister, Bear in mind the carbon fiber skin of a Lancair IV is electrically = conductive so, in general, placing an antenna inside the aircraft = doesn't work for the same reasons aluminum skinned aircraft don't use = internal antennas. I understand there is, or was, an E-glass area in = the vertical fin specifically to provide a non-conductive window for a = dipole type of com antenna but I don't know if that's present in all = L-IV kits. Other than an antenna behind an E-glass section about the = only other option is to use a conventional external com anteanna, = something like a Comant CI122. You mentioned trying dipole antennas on the belly of your airplane. = Again, due to the carbon fiber, I wouldn't expect them to work if they = are placed close to the skin. As for better performance on the ground = that's probably the result of the earth itself acting as a counterpoise = for the antenna. By the way, if you use an external antenna you'll need to make sure it = has an adequate counterpoise (frequently referred to as a ground plane). = I know some of the Legacy builders have had good results using the = carbon fiber skin as the counterpoise as long as the antenna base makes = good electrical contact with the skin. Other builders have used = conductive coatings or copper mesh. There have been a few threads about = this on the LML. Tom Gourley ------=_NextPart_000_004F_01C8664D.FB708770 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Message
Christer,
 
Bear in mind the carbon fiber skin of a = Lancair IV=20 is electrically conductive so, in general, placing an antenna inside the = aircraft doesn't work for the same reasons aluminum skinned aircraft=20 don't use internal antennas.  I understand there is, or was, = an=20 E-glass area in the vertical fin specifically to provide a = non-conductive=20 window for a dipole type of com antenna but I don't know if that's = present=20 in all L-IV kits.  Other than an antenna behind an E-glass = section=20 about the only other option is to use a conventional external com = anteanna,=20 something like a Comant CI122.
 
You mentioned trying dipole antennas on = the belly=20 of your airplane.  Again, due to the carbon fiber, I wouldn't = expect them=20 to work if they are placed close to the skin.  As for better = performance on=20 the ground that's probably the result of the earth itself acting as a=20 counterpoise for the antenna.
 
By the way, if you use an external = antenna you'll=20 need to make sure it has an adequate counterpoise (frequently referred = to as a=20 ground plane).  I know some of the Legacy builders have had good = results=20 using the carbon fiber skin as the counterpoise as long as the antenna = base=20 makes good electrical contact with the skin.  Other builders have = used=20 conductive coatings or copper mesh.  There have been a few threads = about=20 this on the LML.
 
Tom Gourley
 
 
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