X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from elasmtp-dupuy.atl.sa.earthlink.net ([209.86.89.62] verified) by logan.com (CommuniGate Pro SMTP 6.0.9e) with ESMTP id 6863821 for lml@lancaironline.net; Thu, 08 May 2014 09:35:47 -0400 Received-SPF: none receiver=logan.com; client-ip=209.86.89.62; envelope-from=colyncase@earthlink.net DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=dk20050327; d=earthlink.net; b=nt+buPKOgivzKnxSiEPLe1jg6KAuYTf2iZwyfxbO9cEZRb6UlEUBh2iDGXsYqjId; 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 [64.222.160.23] (helo=[192.168.1.24]) by elasmtp-dupuy.atl.sa.earthlink.net with esmtpa (Exim 4.67) (envelope-from ) id 1WiOTf-0000LT-FV for lml@lancaironline.net; Thu, 08 May 2014 09:35:11 -0400 From: Colyn Case Mime-Version: 1.0 (Apple Message framework v1085) Content-Type: multipart/alternative; boundary=Apple-Mail-70-342116010 Subject: Re: [LML] Re: Antennas for 406 MHz ELTs Date: Thu, 8 May 2014 08:35:10 -0500 In-Reply-To: To: "Lancair Mailing List" References: Message-Id: <87413B1A-5C68-4014-948E-C7BDF5C9B476@earthlink.net> X-Mailer: Apple Mail (2.1085) X-ELNK-Trace: 63d5d3452847f8b1d6dd28457998182d7e972de0d01da940989f784dacb5ee19c6d4e42e6ca2319b350badd9bab72f9c350badd9bab72f9c350badd9bab72f9c X-Originating-IP: 64.222.160.23 --Apple-Mail-70-342116010 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=us-ascii so for a carbon air frame, seems like your options are to either put it = in the tail or stick it out the top of the fuselage? On May 7, 2014, at 6:53 AM, John Cooper wrote: Ron and Tom-- But don't the "whip" antennas supplied with the 406 MHz ELTS require a = ground plane? The antenna that comes with the ACK E-04 is clearly = dedigned for external mounting on a metal skin. See: = http://www.aircraftspruce.com/pages/av/elts_zack/whipantennaE04.php = What I am looking for is either a quarter-wave "rubber duck" antenna = that mounts directly to the ELT, or preferably a copper foil half-wave = dipole that I can bond to the inner surface of my aircraft. Being a Ham Radio operator in a former life, I know that a quarter wave = whip antenna is cut for one specific frequency and performance is = degraded at all other frequencies unless some kind of "trap" or = impedance-matching device is installed. Theoretically, a quarter-wave = antenna for 406 MHz should be somewhere around 7" long. For 121.5 MHz it = should be around 23" long. Clearly the whip antennas that come with the = ELT units are cut for some intermediate frequency which is a compromise = that works "OK" at both 406 and 121.5. And what about polarization? The 121.5 and 243MHz signals should be = vertically polarized like your COMM antenna(s), but technically the 406 = MHz should be circularly polarized which would either require a helical = antenna or two crossed dipoles. Of course the polarization would depend = upon whether your aircraft was upright or not :-( > Subject: Re: [LML] Re: Antennas for 406 MHz ELTs > From: Ron Galbraith > Date: 5/6/2014 7:40 AM > I just installed an ME406 ELT. The antenna is around 12-14"long thin = whip and is for 121.5/243.0/406mhz. Installs easily inside a glass = airframe.=20 >=20 > Ron --Apple-Mail-70-342116010 Content-Transfer-Encoding: 7bit Content-Type: text/html; charset=us-ascii so for a carbon air frame,  seems like your options are to either put it in the tail or stick it out the top of the fuselage?

On May 7, 2014, at 6:53 AM, John Cooper wrote:

Ron and Tom--

But don't the "whip" antennas supplied with the 406 MHz ELTS require a ground plane? The antenna that comes with the ACK E-04 is clearly dedigned for external mounting on a metal skin. See: http://www.aircraftspruce.com/pages/av/elts_zack/whipantennaE04.php   What I am looking for is either a quarter-wave "rubber duck" antenna that mounts directly to the ELT, or preferably a copper foil half-wave dipole that I can bond to the inner surface of my aircraft.

Being a Ham Radio operator in a former life, I know that a quarter wave whip antenna is cut for one specific frequency and performance is degraded at all other frequencies unless some kind of "trap" or impedance-matching device is installed. Theoretically, a quarter-wave antenna for 406 MHz should be somewhere around 7" long. For 121.5 MHz it should be around  23" long. Clearly the whip antennas that come with the ELT units are cut for some intermediate frequency which is a compromise that works "OK" at both 406 and 121.5.

And what about polarization? The 121.5 and 243MHz signals should be vertically polarized like your COMM antenna(s), but technically the 406 MHz should be circularly polarized which would either require a helical antenna or two crossed dipoles. Of course the polarization would depend upon whether your aircraft was upright or not :-(

Subject:
Re: [LML] Re: Antennas for 406 MHz ELTs
From:
Ron Galbraith <cfi@instructor.net>
Date:
5/6/2014 7:40 AM		 

I just installed an ME406 ELT.  The antenna is around 12-14"long thin whip and is for 121.5/243.0/406mhz.  Installs easily inside a glass airframe. 

Ron


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