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Author Topic: Nasty RFI in a ford pickup - any hope?  (Read 7297 times)
KG4PID
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Posts: 13




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« Reply #15 on: September 17, 2010, 08:28:17 PM »

Be sure the radio has a good RF ground to the chassis of the truck. I'm working on a HF install in a Ford Freestyle. I had the antenna mounted and ran coax to a radio that was sitting on a small table about 20ft from the car and powered by a 20Ah gel cell for testing. When I started the car it sounded just like the noise in your video and was reading S9. I mounted the radio in the car and used a 1/2 inch ground strap about 5 inches long between the radio and the chassis. When I started the car almost all the noise was gone, YEA! I now have about an S2. This was today BTW. Hope your problem turns out to be this simple.

Max
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K0BG
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« Reply #16 on: September 19, 2010, 06:56:07 AM »

Ah! Here is a factoid for beginners: If grounding the chassis of the transceiver fixes, changes, reduces, or eliminates an apparent RFI problem(s), then something else in the installation was (is) amiss! Just about 99% of the time, it is a poor antenna and/or mounting.
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WK5H
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Posts: 111




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« Reply #17 on: September 23, 2010, 03:09:13 PM »

I've put a ground strap just about everywhere a ground strap can feasibly go; every corner of the aluminum topper to the bed, and every corner of the bed to the frame, from the cab to the frame, from the driver's side hood hinge to the body (passenger side is already done), etc. etc.

Still no relief on 20M, but, it did clear up a bit on the lower bands (40M and down).  Upper bands (17M and up) are still a little noisy.  20M is still just horrible, even with the NB on.

I bought a 10 pack of mix31 snap on ferrite beads, and put one on top of every coil-over plug wire, and no difference.

I took my kenwood HT (TH-F6A which has HF receive), a short piece of coax with about 3/4" of the tip exposed and "sniffed" around the engine compartment...  RFI is radiating from just about every wire under the hood, including the COP wires, injector wires, misc wiring harnesses around the compartment...

One thing I did notice...  The vehicle is VERY resonant around 20M.  I accidentally touched the tip to the aluminum topper, and 20M signals came in like gangbusters.  Thought it was the topper, but, touch to the bumper, and same thing.  Does this have anything/nothing to do with the issues I'm having?
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VE3XKD
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« Reply #18 on: September 24, 2010, 04:05:48 PM »

Hi

I had similar problems with the COP on my Toyota Prius. I carefully wrapped each COP wire and connector in 3M 1181 copper foil tape, and wraped each COP wire back to  the engine chassis as far as i could go. I tack soldered the 3M 1181 seams, and bonded each line to ground. Eventually i cured most fo the noise, and now have only about S2 to S3 to contend with. there is some info on Alan's web site about using 3M 1181. Oh yes, each COP line has as many ferrite beads on the line as i could physically place.

If you are not certain where the noise is coming from, I suggest you make a 1 inch loop probe out of RG 58 or 59, attach the probe to your HF radio, and start listening or probing for the sources of noise. Once you locate a noise source you can either bond it or add ferrites or cover it in 3M 1181 and shield it.



Good luck!
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K1CJS
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« Reply #19 on: October 18, 2010, 05:49:56 AM »

Just because it's not a diesel engine does not mean that injectors can't be causing the noise.  It does sound like the problem is the coil packs, but I would not cross off the fuel injectors from the list.

I have a Merc Grand Marquis that is as quiet as can be when using my HF rig, but I've been told that my case is the exception.
« Last Edit: October 18, 2010, 05:52:31 AM by Chris J. Smith » Logged
K0BG
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« Reply #20 on: October 18, 2010, 07:12:17 AM »

Not really. The Ford COP units are very well designed. Internally, there is a spring which holds down the contact against the plug. It was designed to have a specific reactance. And, there is a chunk of ferrite as well. They are as quiet as any COP on the market, and better than most.
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NY3V
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« Reply #21 on: October 18, 2010, 08:29:29 AM »

My 1997 Ford Escort causes Tremendous hash when I plug my low power MFJ9420 12 watt SSB XCVR into the cigarette lighter jack.

The Surprise was when I used a regulated voltage adjustable switching power supply I bought to power my laptop from the cigarette lighter jack.

It has a slide switch that goes from 15VDC in steps to 24VDC.

I set it to 15VDC and was pleasantly surprised that it reduces the hash to manageable levels. I assume it is because it has a built in ferrite filter on the power cord coming out of the power supply.
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K0BG
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« Reply #22 on: October 18, 2010, 09:41:08 AM »

Well, would it surprise you to know that by raising the input voltage you reduced the RF sensitivity of the front end of the receiver?

Your 1997 Escort uses plug wires. Considering the age, I'd bet that replacing the plugs with new, properly gapped ones, and replacing the plug wires will reduce the noise by quite a bit.

It's a little difficult comparing wired ignition systems to COPs, because the mechanism which generates the impulses you hear is quite a bit different. You really can't bead the offending wiring, as by the time you get enough reactance to quiet things down, you will have integrated the signal enough to cause other problems like delayed ignition pulses.

In the near future, when all-in-one (injector, spark device, and piezo-knock sensor) become common place, we'll have a whole new set of problems to overcome.
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W5WSS
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« Reply #23 on: October 28, 2010, 11:00:38 PM »

I know this is late. I use an older Ford 3.0 litre 6 cyl. with fuel injection. I do not need any filtering with this install. I believe that most of the noise that emanates from the Electra/motor of this automobile is reasonably similar to most automotive vehicles. Having said that perhaps a large extent of your noise would be ignored at the antenna provided the mount is drilled and bolted through the car top and centered. The car body when properly connected to the feedline shielding AT the feed point of the mobile vertical antenna will then act as a Faraday shield and noise pickup will be reduced to it's minimum. The point I am making is that when the antenna is centered in this fashion it is blocking more of the noises that are generated and helping to prevent noise ingress in the first place so there are advantages in biting the bullet and drilling those nasty holes through the roof top of the ham operators vehicle. I know for a fact if I placed my antenna anywhere else around the carbody my noise would simply increase...and that is without attacking the noise at the source just by locating it in the best spot to begin with. 73
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K0BG
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« Reply #24 on: October 29, 2010, 12:37:56 PM »

Well, Robert, I wish it were that simple! It isn't!

A vehicle body is not a Faraday shield in the correct sense. Yes, high mounting does help the RFI noise situation, but not in the reasons you state. The whole key it to minimize ground losses, by making most of the RF current flow through the vehicle's superstructure, rather than the lossy surface under the vehicle. Proper mounting helps, and does height if the added height mounting scheme doesn't add more ground loss (mounting atop a long stalk for example).

Probably the most effective thing you can do to reduce RFI beside good mounting, is to bond all of the horizontal surfaces like the hood, trunk, and the exhaust system. Do it right, and top of fender or quarter panel works just as well as roof mounting. Maybe better, it is allows a longer overall length. Remember, radiation resistance is a square factor of electrical length.
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K1CJS
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« Reply #25 on: November 08, 2010, 09:40:07 AM »

BTW, my Grand Marquis isn't one with the COP design--it also has wires with 2 dual spark packs, one on either side of the front of the engine.  It also has individual cylinder fuel injection.  The plug wires have been replaced with original equipment Motorcraft wires a couple of years ago along with the plugs.  That is possibly the main reason I have no noticeable RFI in my car except for a tiny bit of whine--that I ignore.
« Last Edit: November 08, 2010, 09:45:51 AM by Chris J. Smith » Logged
K8KAS
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Posts: 569




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« Reply #26 on: November 09, 2010, 08:59:43 AM »

I have never seen a Ford product without a fuel pump noise problem, yes Ford does have a fix called
the "TDOT fuel pump noise filter" required by all Fords sold to the Texas Dept of Trans. You can also
see ARRL RFI/EMC Handbook for a filter design/simple and works great for the fuel pump motor. I have seen a number of pump filters in QST and other rags. When I install at the pump the simple filters mentioned usually 90% of the vehicle noise is gone period.  Denny K8KAS 73
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