Return-Path: Received: from uhura.concentric.net ([206.173.118.93]) by ns1.olsusa.com (Post.Office MTA v3.5.3 release 223 ID# 0-64832U3500L350S0V35) with ESMTP id com for ; Mon, 5 Jun 2000 00:41:34 -0400 Received: from cliff.concentric.net (cliff.concentric.net [206.173.118.90]) by uhura.concentric.net (8.9.1a/(98/12/15 5.12)) id AAA06489; Mon, 5 Jun 2000 00:47:36 -0400 (EDT) [1-800-745-2747 The Concentric Network] Received: from [207.155.173.141] (ts008d33.lon-co.concentric.net [207.155.173.141]) by cliff.concentric.net (8.9.1a) id AAA03283; Mon, 5 Jun 2000 00:47:33 -0400 (EDT) Errors-To: User-Agent: Microsoft-Outlook-Express-Macintosh-Edition/5.02.2022 Date: Sun, 04 Jun 2000 22:45:25 -0600 Subject: Re: Proper polarization of the ELT antannae From: Ron Galbraith-CFII To: "INTERNET:lancair.list@olsusa.com" Message-ID: In-Reply-To: <200006040943_MC2-A764-89BC@compuserve.com> X-Mailing-List: lancair.list@olsusa.com Mime-Version: 1.0 <<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> << Lancair Builders' Mail List >> <<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> >> Just some more comments. Actually you are all pretty much correct in the Vertical/Horizontal thing, however, most VHF antennas on airplanes are not true vertical antennas. They are usually swept back somewhat for aerodynamics. There is about a 20db difference in a true vertical to Horizontal polarization, which is huge (about 95 times), but if you use a 45 degree antenna, then the difference between horizontal to vertical is only about 3db (2 times). I doubt that when you really need to use this antenna, it is going to be truely vertical, or horizontal, and I think the best orientation would be to install it somewhere where it is not in close proximity to any other antennas, or other metals of any kind, and wherever that ends up via vertical or horizontal will be just fine. The satellites that receive the signal, and pinpoint the location of ELT's receive circular polarization, which means that it doesn't matter if it's horizontal or vertical, it will receive the signal the same. At the VHF frequencies, the signal will actually reflect off of mountains, buildings, or whatever is there, and spread the signal out to vertical and horizontal signals anyway, so don't spend alot of time with making it flat, or straight up. Just keep it away from other possible interference, and make sure it is resonant to 121.5Mhz using a high quality SWR meter. Ron Galbraith LNCE - N5ES (40%) >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> LML website: http://www.olsusa.com/Users/Mkaye/maillist.html LML Builders' Bookstore: http://www.buildersbooks.com/lancair Please send your photos and drawings to marvkaye@olsusa.com. >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>