X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from elasmtp-spurfowl.atl.sa.earthlink.net ([209.86.89.66] verified) by logan.com (CommuniGate Pro SMTP 6.0.7) with ESMTP id 6577694 for lml@lancaironline.net; Tue, 05 Nov 2013 13:39:19 -0500 Received-SPF: none receiver=logan.com; client-ip=209.86.89.66; envelope-from=colyncase@earthlink.net DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=dk20050327; d=earthlink.net; b=daH4E5MqbWsq00MAeMpk07UpmjFnwvQds2MFCe5XYUNb9M4/EEFs8azPDhxnNxo2; h=Received:From:Mime-Version:Content-Type:Subject:Date:In-Reply-To:To:References:Message-Id:X-Mailer:X-ELNK-Trace:X-Originating-IP; Received: from [70.16.215.180] (helo=[192.168.1.24]) by elasmtp-spurfowl.atl.sa.earthlink.net with esmtpa (Exim 4.67) (envelope-from ) id 1VdlWW-0007Z1-K2 for lml@lancaironline.net; Tue, 05 Nov 2013 13:38:44 -0500 From: Colyn Case Mime-Version: 1.0 (Apple Message framework v1085) Content-Type: multipart/alternative; boundary=Apple-Mail-87--504885320 Subject: Re: [LML] Re: TXPDR antenna Date: Tue, 5 Nov 2013 13:38:43 -0500 In-Reply-To: To: "Lancair Mailing List" References: Message-Id: <9BAB3A5E-E4D0-4EDA-8FC4-FBBE1553577B@earthlink.net> X-Mailer: Apple Mail (2.1085) X-ELNK-Trace: 63d5d3452847f8b1d6dd28457998182d7e972de0d01da9404ba5240c37598c6f17aac968d0c40caa350badd9bab72f9c350badd9bab72f9c350badd9bab72f9c X-Originating-IP: 70.16.215.180 --Apple-Mail-87--504885320 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=windows-1252 pretty good but not perfect conductor. ...but you need to grind through = the resin to electrically connect to the carbon fiber. example: I don't think gps antennas function under carbon. On Nov 5, 2013, at 1:16 PM, Nick Long wrote: Hello, =20 Obviously I don=92t know the installation in question, but let me offer = my 2cents. My day job is as an RF engineer. =20 A metal ground plane is much better than paint. But it doesn=92t have to = be any significant thickness. Foil, or sticky back foil or tape is ok. =20 The reason for needing a ground plane is because the structure is non = conducting. Effectively the structure is not there as far as the radio = signal is concerned, so it=92s just as good to put the ground plane on = the inside, which is a bit easier. =20 Follow that logic through and you come to the idea that the whole = antenna can be inside, providing you can set up a suitable ground plane = or equivalent. =20 The difficulty comes if the aircraft structure is partly conducting, = rather than insulating, and therefore absorbs radio energy instead of = being transparent to it. This is where there=92s a gap in my knowledge =96= I don=92t know the electrical characteristics of carbon fibre. I = suspect it can be treated as an insulator, but maybe someone can confirm = that. =20 Nick Long =20 =20 From: Colyn Case Sent: Tuesday, November 5, 2013 1:36 PM To: Lancair Mailing List Subject: [LML] Re: TXPDR antenna =20 John, I'm trying to figure out how a xponder antenna would be between = the rudder pedals and the firewall. Paint works at first but can fracture. A physically robust connection to the ground plane is best. If it were me I would take the antenna off (assuming it's outdoors like = it should be), grind through all the filler down to the carbon, install = a small sheet metal ground plane, provide a good strong contact area, = reassemble, and then bodywork over the remaining visible ground plane. =20 Colyn =20 On Nov 5, 2013, at 7:46 AM, John Barrett wrote: =20 Hello all, =20 Behind the rudder pedal the antenna for the transponder can be ID'd by = the brown Rg cable. =20 ATC sometimes loses my squawk and I am thinking I need to add a ground = plane. Question for the group is if I can paint conductive paint around = the antenna and under neath the hydraulic lines as much as possible. = Will the Jeffco tank sealer interfere with effecitveness? Do I need to = remove the antenna or can the hub be painted to provide continuity? =20 Any suggestions welcome. =20 Thanks, John Sent from my iPad =20 Begin forwarded message: > From: John Barrett <2thman1@gmail.com> > Date: November 4, 2013 at 12:47:56 PM PST > To: John Barrett >=20 >=20 >=20 > >=20 >=20 >=20 > Sent from my iPhone =20 --Apple-Mail-87--504885320 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=windows-1252
Hello,
 
Obviously I don=92t know the installation in question, but let me = offer my=20 2cents. My day job is as an RF engineer.
 
A metal ground plane is much better than paint. But it doesn=92t = have to be=20 any significant thickness. Foil, or sticky back foil or tape is = ok.
 
The reason for needing a ground plane is because the structure is = non=20 conducting. Effectively the structure is not there as far as the radio = signal is=20 concerned, so it=92s just as good to put the ground plane on the inside, = which is=20 a bit easier.
 
Follow that logic through and you come to the idea that the whole = antenna=20 can be inside, providing you can set up a suitable ground plane or=20 equivalent.
 
The difficulty comes if the aircraft structure is partly = conducting, rather=20 than insulating, and therefore absorbs radio energy instead of being = transparent=20 to it. This is where there=92s a gap in my knowledge =96 I don=92t know = the electrical=20 characteristics of carbon fibre. I suspect it can be treated as an = insulator,=20 but maybe someone can confirm that.
 
Nick Long
 
 
From: Colyn Case
Sent: Tuesday, November 5, 2013 1:36 PM
Subject: [LML] Re: TXPDR antenna
 
John,  I'm trying to figure out how a xponder antenna would be = between=20 the rudder pedals and the firewall.
Paint works at first but can = fracture.=20
A physically robust connection to the ground plane is best.
If it were me I would take the antenna off (assuming it's outdoors = like it=20 should be), grind through all the filler down to the carbon, install a = small=20 sheet metal ground plane, provide a good strong contact area, = reassemble, and=20 then bodywork over the remaining visible ground plane.
 
Colyn
 
On Nov 5, 2013, at 7:46 AM, John Barrett wrote:
 
Hello all,
 
Behind the rudder pedal the antenna for the transponder can be ID'd = by the=20 brown Rg cable.
 
ATC sometimes loses my squawk and I am thinking I need to add a = ground=20 plane.  Question for the group is if I can paint conductive paint = around=20 the antenna and under neath the hydraulic lines as much as = possible.  Will=20 the Jeffco tank sealer interfere with effecitveness?  Do I need to = remove=20 the antenna or can the hub be painted to provide continuity?
 
Any suggestions welcome.
 
Thanks,
John

Sent from my iPad=20
 

Begin forwarded message:

From: John Barrett <2thman1@gmail.com>
Date:=20 November 4, 2013 at 12:47:56 PM PST
To: John Barrett <jbarrett@carbinge.com>


<photo.JPG>



Sent = from my=20 iPhone
 

= --Apple-Mail-87--504885320--