X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from [66.219.56.248] (HELO qnsi-xch.qnsi.net) by logan.com (CommuniGate Pro SMTP 5.0.8) with ESMTP id 987547 for flyrotary@lancaironline.net; Thu, 16 Feb 2006 12:43:05 -0500 Received-SPF: none receiver=logan.com; client-ip=66.219.56.248; envelope-from=bhughes@qnsi.net Content-class: urn:content-classes:message Return-Receipt-To: "Bobby J. Hughes" MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Disposition-Notification-To: "Bobby J. Hughes" X-MimeOLE: Produced By Microsoft Exchange V6.5.6944.0 Subject: RE: [FlyRotary] Re: Radio noise saga Date: Thu, 16 Feb 2006 11:43:37 -0600 Message-ID: X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: [FlyRotary] Re: Radio noise saga Thread-Index: AcYzGyAjDUoaqgF/SQ+QoMi60ADmwwAAvt3Q From: "Bobby J. Hughes" To: "Rotary motors in aircraft" Barry, If you are using a metallic conduit then I would ground the conduit at one location. Power or signal. I do not think running an exposed shield would have any effect or offer any EMI protection.=20 Avoid all ground loops. One point grounds on all shielded wire. Incidental grounding can create loops depending on contact area. Not likely a problem in a composite airframe.=20 Keep signal / radio ground isolated from motor grounds return leads, lights, etc, where possible. On your ground / return buss you can connect the negative return / ground lead in the middle. Connect the clean stuff to one side of the buss bar and the dirty stuff to the other side so the clean stuff has a clean path to ground.=20 Make sure signal cables and power cables are not twisted or mixed together. Signal cable woven between large power cable can get dirty.=20 Bobby=20 -----Original Message----- From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Barry Gardner Sent: Thursday, February 16, 2006 11:03 AM To: Rotary motors in aircraft Subject: [FlyRotary] Re: Radio noise saga Bill and other knowledgable folks, Is there any value in running a braided shielding inside the conduit that will carry the power leads? I'm building a plane like Buly's and want to know if that's something I should just build into my electrical raceway. Thanks. Barry Gardner Wheaton, IL Bill Dube wrote: > The separated power leads radiate noise quite well. They are a giant=20 > loop antenna that is transmitting any ripple on the current to the=20 > battery. Alternator whine, motor whine, ingnition system input ripple=20 > all will radiate from such a loop. > > This is a very common problem on homebuilt electric vehciles. With the > large battery pack, folks often fine it convienient to run the power=20 > leads up one side of the car and back on the other. The hash from the=20 > motor controller and/or the charger make it impossible to use anything > electronic inside the car if you wire it that way. Sometimes, the=20 > motor controller throttle input will pick up the output hash from such > a loop and make the car undrivable. > > Always run power leads as a pair. Keep the "presented area" low to=20 > reduce the transmitted noise. > > You have found the problem. > > >> >> Twisted pair only reduces noise in signals transmitted THROUGH the=20 >> wire, and it only works if the receiver uses a differential signal. >> It doesn't help with power wires. The curious can drop by: >> >> http://www.duxcw.com/digest/Howto/network/cable/cable4.htm >> >> It's a fairly good, brief description of what goes on. You'll usually >> only find twisted pair in LAN cabling. >> >> Regards, >> Chad >> >> -- >> Homepage: http://www.flyrotary.com/ >> Archive and UnSub: http://mail.lancaironline.net/lists/flyrotary/ >> > > -- > Homepage: http://www.flyrotary.com/ > Archive and UnSub: http://mail.lancaironline.net/lists/flyrotary/ > -- Homepage: http://www.flyrotary.com/ Archive and UnSub: http://mail.lancaironline.net/lists/flyrotary/