X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml Date: Thu, 23 Nov 2006 14:06:52 -0500 Message-ID: X-Original-Return-Path: Received: from smtp103.sbc.mail.mud.yahoo.com ([68.142.198.202] verified) by logan.com (CommuniGate Pro SMTP 5.1.2) with SMTP id 1597301 for lml@lancaironline.net; Thu, 23 Nov 2006 13:39:45 -0500 Received-SPF: none receiver=logan.com; client-ip=68.142.198.202; envelope-from=elippse@sbcglobal.net Received: (qmail 42832 invoked from network); 23 Nov 2006 18:38:02 -0000 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=sbcglobal.net; h=Received:X-YMail-OSG:Message-ID:From:To:Subject:Date:MIME-Version:Content-Type:X-Priority:X-MSMail-Priority:X-Mailer:X-MIMEOLE; b=lU3h4C7lY+UZbUDWNG8JgCEYKOzs5r033m7qtV+U1oyPd8Ldw7Y2MW868Fv4UovSsKIp7vDyWihoONLEAfd/DWIB+0Bjk4Xx2L6A6h2rm6f3njorZpEnRj4uvcoXMdJxGR3/MpWXNFEfwTfb+vFoppHt2zfYa0Fkvn/hs4t6eOE= ; Received: from unknown (HELO Computerroom) (elippse@sbcglobal.net@75.15.146.95 with login) by smtp103.sbc.mail.mud.yahoo.com with SMTP; 23 Nov 2006 18:38:02 -0000 X-YMail-OSG: 8F8ZsgYVM1l5VG634qxd8_z3MIjhtpLzdy5UEpM5o7ndWl1LY8NsuXU4JgYl_jAdRW0Yh0XhzKvMEw1gTLvm5ozEDd9..QTcBj1N6WDEtdyKYY.LUwLnIw-- X-Original-Message-ID: <000901c70f2e$85242800$5f920f4b@Computerroom> From: "Paul Lipps" X-Original-To: "Marv Kaye" Subject: Nav Antenna X-Original-Date: Thu, 23 Nov 2006 10:37:46 -0800 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0006_01C70EEB.6DA71B80" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.2869 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2900.2962 This is a multi-part message in MIME format. ------=_NextPart_000_0006_01C70EEB.6DA71B80 Content-Type: text/plain; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable An antenna in free-space may have the nice toroidal, donut-shaped = pattern, but when mounted on some vehicle, its pattern may be distorted, = leaving holes or nulls in various directions. These nulls may be caused = by blockage, but more often due to nearby metallic objects which = re-radiate the signal at some phase angle which may be destructive. = Consider, for example, elevator and aileron push-pull tubes and wiring. = When these are of a length that is an apprecible fraction of the average = 105" wavelength, and are within a wavelength, and somewhat parrallel, = interesting things happen to the toroidal pattern; it's as if your cat = was taking bites out of the donut. If you have fibreglass wings, the LE of the wing root is a good = mounting place for the horizontally-polarized nav signal. A = signal-splitter has an inherent loss of dividing the signal power to = each receiver, so if you have two receivers, each will receive slightly = less than 1/2 power, a 3dB loss. That shouldn't be too bad for a = close-up localizer. A tip-off that destructive interference is taking = place is that the reception changes with frequency, some channels being = better than others. As far as GS is concerned, that's a much higher = frequency, so it should not have coincident loss of signal. That would = seem to be more in line with some blockage. Are the nav and GS antennas = coincident in mounting? You might also check each coax for poor = connections that allow leakage at the connector which also can be = destructive, as well as possibly a shorted coax. Get hold of a SWR = tester and check these lines. ------=_NextPart_000_0006_01C70EEB.6DA71B80 Content-Type: text/html; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable

An antenna in free-space may = have the=20 nice toroidal, donut-shaped pattern, but when mounted on some vehicle, = its=20 pattern may be distorted, leaving holes or nulls in various directions. = These=20 nulls may be caused by blockage, but more often due to nearby metallic = objects=20 which re-radiate the signal at some phase angle which may be = destructive.=20 Consider, for example, elevator and aileron push-pull tubes and wiring. = When=20 these are of a length that is an apprecible fraction of the average 105" = wavelength, and are within a wavelength, and somewhat parrallel, = interesting=20 things happen to the toroidal pattern; it's as if your cat was taking = bites out=20 of the donut.

If you have fibreglass wings, = the LE of=20 the wing root is a good mounting place for the = horizontally-polarized nav=20 signal. A signal-splitter has an inherent loss of dividing the signal = power to=20 each receiver, so if you have two receivers, each will receive slightly = less=20 than 1/2 power, a 3dB loss. That shouldn't be too bad for a close-up = localizer.=20 A tip-off that destructive interference is taking place is that the = reception=20 changes with frequency, some channels being better than others. As = far as=20 GS is concerned, that's a much higher frequency, so it should not have=20 coincident loss of signal. That would seem to be more in line with some=20 blockage. Are the nav and GS antennas coincident in mounting? You might = also=20 check each coax for poor connections that allow leakage at the connector = which=20 also can be destructive, as well as possibly a shorted coax. Get = hold of a=20 SWR tester and check these lines.

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