Return-Path: Sender: "Marvin Kaye" To: lml@lancaironline.net Date: Fri, 28 Jan 2005 21:21:32 -0500 Message-ID: X-Original-Return-Path: Received: from lakermmtao06.cox.net ([68.230.240.33] verified) by logan.com (CommuniGate Pro SMTP 4.2.8) with ESMTP id 627168 for lml@lancaironline.net; Fri, 28 Jan 2005 20:49:45 -0500 Received-SPF: none receiver=logan.com; client-ip=68.230.240.33; envelope-from=danobrien@cox.net Received: from Dan.cox.net ([68.100.82.159]) by lakermmtao06.cox.net (InterMail vM.6.01.04.00 201-2131-117-20041022) with ESMTP id <20050129014915.ZJPT7687.lakermmtao06.cox.net@Dan.cox.net>; Fri, 28 Jan 2005 20:49:15 -0500 X-Original-Message-Id: <6.2.0.14.0.20050128204604.01cad548@127.0.0.1> X-Mailer: QUALCOMM Windows Eudora Version 6.2.0.14 X-Original-Date: Fri, 28 Jan 2005 20:49:13 -0500 X-Original-To: lml@lancaironline.net,Lancair_ES@yahoogroups.com From: Dan O'Brien Subject: Pretty darned confused about grounding shields Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="=====================_10551656==.ALT" --=====================_10551656==.ALT Content-Type: text/plain; charset="us-ascii"; format=flowed (Posted this on the aeroelectric list. Probably worth posting here as well. Guess the ultimate question is: what works?) After Wayne Sweet suggested the Garmin manual was off regarding shielding, I called the company. Ready for this? 1. Connecting a UPS SL30 Nav Com to a MD200-306 CDI indicator: UPS manual (before the Garmin merger) says ground shields at both ends. They are SPECIFIC. For example, they have footnotes that explicitly say to ground a both ends, while they also have footnotes saying to let float the Nav/Com end of the connection to the audio panel. Couldn't be more explicit. However, the Garmin tech rep says to ground the shields only at the Nav/Com end. He says "I don't know why the manual says that?" 2. Connecting a GNS430 GPS/Nav/Com to a MD200-306 CDI indicator: Garmin manual says ground shields at both ends. However, the Garmin tech rep says to ground the shields only at the Nav/Com end. He says "I don't know why the manual says that?" 3. Connecting a GNS430 to an altitude serializer: Garmin manual says ground the shield at both ends. However, the Garmin tech rep says to ground the shield only at the Garmin end; while the Microencoder rep says ground the shield at the Microencoder end (the "sending" end). Almost as bad as economists (my field). OK scientists, there either IS a right answer to each question, or there are tradeoffs that are worth understanding. Inquiring (if somewhat mystified, and a little irritated) minds want to know. --=====================_10551656==.ALT Content-Type: text/html; charset="us-ascii" (Posted this on the aeroelectric list. Probably worth posting here as well. Guess the ultimate question is: what works?)

After Wayne Sweet suggested the Garmin manual was off regarding shielding, I called the company. Ready for this?

1. Connecting a UPS SL30 Nav Com to a MD200-306 CDI indicator: UPS manual (before the Garmin merger) says ground shields at both ends. They are SPECIFIC. For example, they have footnotes that explicitly say to ground a both ends, while they also have footnotes saying to let float the Nav/Com end of the connection to the audio panel. Couldn't be more explicit.

However, the Garmin tech rep says to ground the shields only at the Nav/Com end. He says "I don't know why the manual says that?"

2. Connecting a GNS430 GPS/Nav/Com to a MD200-306 CDI indicator: Garmin manual says ground shields at both ends.

However, the Garmin tech rep says to ground the shields only at the Nav/Com end. He says "I don't know why the manual says that?"

3. Connecting a GNS430 to an altitude serializer: Garmin manual says ground the shield at both ends.

However, the Garmin tech rep says to ground the shield only at the Garmin end;

while the Microencoder rep says ground the shield at the Microencoder end (the "sending" end).

Almost as bad as economists (my field). OK scientists, there either IS a right answer to each question, or there are tradeoffs that are worth understanding. Inquiring (if somewhat mystified, and a little irritated) minds want to know.

--=====================_10551656==.ALT--