X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Fri, 02 Apr 2010 11:08:16 -0400 Message-ID: X-Original-Return-Path: Received: from smtp-auth-05.mx.pitdc1.expedient.net ([206.210.66.138] verified) by logan.com (CommuniGate Pro SMTP 5.3.5) with ESMTPS id 4193271 for lml@lancaironline.net; Fri, 02 Apr 2010 09:08:47 -0400 Received-SPF: none receiver=logan.com; client-ip=206.210.66.138; envelope-from=rpastusek@htii.com Received: from HTBOB001 (static-72-66-86-7.washdc.fios.verizon.net [72.66.86.7]) by smtp-auth-05.mx.pitdc1.expedient.net (Postfix) with ESMTPSA id E13F7E57CF for ; Fri, 2 Apr 2010 09:08:11 -0400 (EDT) From: "Robert Pastusek" X-Original-To: "'Lancair Mailing List'" References: In-Reply-To: Subject: RE: [LML] GPS reception issue X-Original-Date: Fri, 2 Apr 2010 09:08:10 -0400 X-Original-Message-ID: <037b01cad265$8c3d06e0$a4b714a0$@com> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_037C_01CAD244.052B66E0" X-Mailer: Microsoft Office Outlook 12.0 Thread-Index: AcrSYQYh9TWQCQoLREKMtRKnQuY+YgAAvVUw Content-Language: en-us This is a multi-part message in MIME format. ------=_NextPart_000_037C_01CAD244.052B66E0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Keith, The GPS signal is very weak, and easily blocked/jammed. To avoid such issues, I mounted my GPS antennae (2) on the top of the fuselage, behind the door (IV-P, but the concept is the same on any aircraft). It needs to "see" a large part of the sky at all times, and the area it needs is dependent on the sight line to several satellites, all in different positions at any time. Consider relocating your antenna as a good fix for the sight line issue. Two other considerations: Use RG400 or better cable to connect the antenna to the unit.or the originally supplied cable if you have it. RG58 is not good enough, nor will "TV hookup cable" do the job. Also, CAREFULLY check the antenna gain against the requirements of your unit, and that you are using the correct (active or passive) antenna for your GPS. All of these are potential "gottchas," but when you finally get it working reliably, it's a thing of beauty! Good luck, Bob The signal reception on my Garmin 420 is really dodgy. We've tested the unit on a bench and it worked great. We've swapped the antenna, no change. We swapped the antenna cable, it actually got quite a bit worse (the old one had intermittent issues, the new one is dodgy, nearly full time.) If I route the cable 'just so', I can make it work fairly well on the ground with the canopy open, but it tends to go to hell when I close the canopy. If I unscrew and lift the glare shield about 1/2" - 1", the reception is great. The GPS antenna is attached to the top of the glare shield on the co-pilot side. I'm going to get some help from a shop in debugging this...but it seems to me that part of the canopy is either causing interference within the antenna cable, or the antenna itself. Has anyone experienced anything like this before? This is in a 360. Keith ------=_NextPart_000_037C_01CAD244.052B66E0 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

Keith,

The GPS signal is very weak, and easily blocked/jammed. = To avoid such issues, I mounted my GPS antennae (2) on the top of the fuselage, = behind the door (IV-P, but the concept is the same on any aircraft). It needs to = “see” a large part of the sky at all times, and the area it needs is dependent = on the sight line to several satellites, all in different positions at any = time. Consider relocating your antenna as a good fix for the sight line = issue.

Two other considerations: Use RG400 or better cable to = connect the antenna to the unit…or the originally supplied cable if you = have it. RG58 is not good enough, nor will “TV hookup cable” do the = job. Also, CAREFULLY check the antenna gain against the requirements of your = unit, and that you are using the correct (active or passive) antenna for your = GPS. All of these are potential “gottchas,” but when you finally = get it working reliably, it’s a thing of beauty!

Good luck,

Bob

The signal reception on my Garmin 420 is really = dodgy. We've tested the unit on a bench and it worked great. We've = swapped the antenna, no change. We swapped the antenna cable, it actually got quite = a bit worse (the old one had intermittent issues, the new one is dodgy, nearly = full time.)

If I route the cable 'just so', I can make it work fairly well on the = ground with the canopy open, but it tends to go to hell when I close the = canopy.

If I unscrew and lift the glare shield about 1/2" - 1", the = reception is great. The GPS antenna is attached to the top of the glare = shield on the co-pilot side.

I'm going to get some help from a shop in debugging this...but it seems = to me that part of the canopy is either causing interference within the = antenna cable, or the antenna itself.

Has anyone experienced anything like this before? This is in a 360.

Keith

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