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Re: [RFI] Ferrite Beads from DX Engineering

To: "WA3GIN" <wa3gin@comcast.net>
Subject: Re: [RFI] Ferrite Beads from DX Engineering
From: dgsvetan@rockwellcollins.com
Date: Mon, 11 Jan 2010 17:18:29 -0600
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>

I would say that the recommendation given to you was, in fact, a pretty 
good starting point.  After all, when you consider the nature of the 
ignition system waveform, and the fact that in many vehicles today, each 
plug is fired by its own dedicated high voltage circuit (no more 
distributors), putting at least one bead on each spark plug lead is a 
reasonable first step.  If you only do a few, you are likely to get little 
or no useful results.  Of course, if you can determine that SOME 
particular wires are more troublesome than others, by all means, treat 
only those and see what happens.

Be advised that for some vehicles, full RFI suppression can make the DXE 
proposal look like a bargain basement sale.  A fellow aerospace engineer 
in CA had some real problems with his import SUV or pickup (I don't recall 
make/model) several years ago.  He did submit an article on his cure to 
QST, but I am not sure it was published.  I did see the submitted master 
article, with photographs, and in this instance, full suppression to make 
an Icom 706 useable in the vehicle required FULLY shielded ignition wires, 
a fully metal-plated distributor cap (for terminating the ignition wire 
shields), and special fittings for connecting the wire shields at the 
cylinder head end.  (Without terminating the shield at both ends to the 
engine chassis, the shields were ineffective.)  He also added lots of 
bonding braids between various parts of the vehicle, as well as bonding 
the exhaust pipe to chassis so that it was no longer a radiating antenna.

Good luck.  Many successful vehicular RFI solutions do take a lot of time, 
patience, engineering thought, and yes, cash.

73, Dale


"WA3GIN" <wa3gin@comcast.net> 
Sent by: rfi-bounces@contesting.com
01/11/2010 04:53 PM

"Peter Laws" <plaws0@gmail.com>, <rfi@contesting.com>

Re: [RFI] Ferrite Beads from DX Engineering


I asked the DX Engineering fella how best to approach the RFI and he said, 

start with one clamp on per spark wire, then just add more in series till 
the noise is reduced.  That doesn't like an inexpensive solution to me and 
don't think it will work either, haha.

If I win the lotto I'll buy new spark wires and install 15 beads each and 
report the results ;-)

----- Original Message ----- 
From: "Peter Laws" <plaws0@gmail.com>
To: <rfi@contesting.com>
Sent: Monday, January 11, 2010 5:45 PM
Subject: Re: [RFI] Ferrite Beads from DX Engineering

On Mon, Jan 11, 2010 at 15:23, Jim Brown <jim@audiosystemsgroup.com> 

> Ferrite beads in pulsed circuits (like spark plug wires) would work
> slightly differently. There, they work by slowing down the rise/fall
> time of the current pulse (or smoothing its corners), which in turn
> reduces the strength of harmonics. It's those harmonics that we hear


Well, I mean not "really" as in "you don't know what you're talking
about" but as in "wow, the SAE types spend a lot of time getting those
rise-fall times just right so that the car meets the applicable
standards for fuel consumption and emissions" ...  Although not
mandated, there are also drivability concerns as well ...

Just how much would chokes change that?  And how does this compare to
the old "resistor plugs" that were sold to make the ticking on the car
radio go away?

Peter Laws | N5UWY | plaws plaws net | Travel by Train!
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