AeroElectric-List Digest Archive

Thu 02/26/15


Total Messages Posted: 3



Today's Message Index:
----------------------
 
     1. 06:24 AM - Re: Shield grounds (Eric M. Jones)
     2. 06:52 AM - Re: Shield grounds (Robert L. Nuckolls, III)
     3. 08:21 PM - Re: Handheld transceiver alternate antenna (jrevens)
 
 
 


Message 1


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    Time: 06:24:56 AM PST US
    Subject: Re: Shield grounds
    From: "Eric M. Jones" <emjones@charter.net>
    Here is the ultimate authority on the subject: http://eeeic.eu/proc/papers/55.pdf Also see my attachment on the subject. -------- Eric M. Jones www.PerihelionDesign.com 113 Brentwood Drive Southbridge, MA 01550 (508) 764-2072 emjones(at)charter.net Read this topic online here: http://forums.matronics.com/viewtopic.php?p=438765#438765 Attachments: http://forums.matronics.com//files/dabbling_with_electricity_137.pdf


    Message 2


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    Time: 06:52:35 AM PST US
    From: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
    Subject: Re: Shield grounds
    At 16:26 2015-02-25, you wrote: ><matronics.list@gmail.com> > >I thought I understood how shield grounds worked and how to >implement them but now looking at a Garmin G3X. The garmin manual >specifically has some of the shields terminated on both ends and >grounded. some of the shields are only terminated and grounder on >one end and the other is floating. So what is the proper >termination of shields and what is the science behind the proper methods. The 'shielding' feature of a conductor wrapped about a central wire or collection of wires is to break potential electro-static coupling between said wires and any other wires. Wires inside a shield can be EITHER a potential antagonist (like p-leads) or victim (audio wires). Shielding allows potential victims and antagonists to share the same wire bundles. Since the shield is also a conductor, the system designer may . . . and often does . . . use the shield for both electro-static barrier AND as some functional flow of energy from one item to another. Obviously, in this case BOTH ends of a shield may be terminated. Sometimes, shielded wire is used as two conductor cable and both ends of the shield are terminated even if wires within the shielding are neither potential victim or antagonist. I have used shielded wire to build flying leads off an LED annunciators to exploit the nice round characteristic of the shielded wire versus say, an open twisted pair. I have used shielded trios to wire a 4-conductor power/control path even tho the shielding is not REQUIRED . . . only handy. When the shield is applied ONLY for a barrier to electro-static coupling, the general practice is to terminate ONE END only. Terminating the other end may not be a bad idea but it is unnecessary and offers a low risk for creating a 'ground loop' that was not foreseen by the installer . . . or perhaps event the system designer. Bottom line: Don't second guess the system designer. Wire per installation instructions. Bob . . .


    Message 3


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    Time: 08:21:46 PM PST US
    Subject: Re: Handheld transceiver alternate antenna
    From: "jrevens" <jrevens@comcast.net>
    My thanks to all... there was a lot more input than I thought there would be. Lots of good information and ideas. I believe I like some sort of the patch cable idea best... don't want any more antennas, devices and wiring than necessary. I'll just do it like I did my T-18, 25 years ago, only (hopefully) a little cleaner and more accessible. John Evens Thorp T-18 N71JE (built & flying) Kitfox SS7 N27JE (building) Read this topic online here: http://forums.matronics.com/viewtopic.php?p=438792#438792




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