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Re: [RFI] Auto quieting

To: rfi@contesting.com
Subject: Re: [RFI] Auto quieting
From: CR <ka5s@earthlink.net>
Reply-to: ka5s@earthlink.net
Date: Mon, 5 Oct 2015 04:35:58 -0400
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>
On 10/5/2015 1:16 AM, Mike Ryan wrote:
In my case I use inch wide tinned copper strap which cut to lengths as required. I think you would find the flat strap superior to round wire due to the additional surface area they provide. - Mike

Different problems may take different solutions.

To carry RF current between poorly bonded body parts we will need low resistance, low inductance bonds, the proverbial short, wide strap or large gauge wire, sometimes (not always) several of them, in different places. To discharge static electricity, higher resistance, higher inductance connections will do , even rather high value wire wound resistors, and there is no need for copper when stainless steel will do, if not over-flexed. There are other ways to deal with other sources of static; I typically use a base-inductance or choke (even the L-match) to eliminate the occasional tick, tick, tick, pockpockpock whirrrrrr WHAM! of precipitation static discharging through gas-tube protectors.

Braid is notoriously prone to fail one strand at a time; my last employer sold electronic systems into the aircraft market*, and that had to be bonded to the airframe or other system ground (think composites) with durable, short, heavy, low resistance strap or wire. The usual requirement was no more than 2.5 milli-ohms from chassis to airframe, as aircraft quite often carry thousands of Amperes of lightning current and it does interconnected equipment some distance apart no good at all to have more voltage appearing on power and signal conductors from some distance away than internal protectors can deal with.

*Interesting info: http://www.interferencetechnology.com/new-emc-requirements-for-commercial-avionics-rtcado-160f/ ; http://incompliancemag.com/article/design-practices-for-military-emc-and-environmental-compliance/; www.dtic.mil/dtic/tr/fulltext/u2/a509335.pdf

Cortland Richmond
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