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Author Topic: Nasty RFI in a ford pickup - any hope?  (Read 7105 times)
WK5H
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Posts: 111




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« on: September 07, 2010, 05:24:56 PM »

I apologize first off if this is going in the wrong topic (there is an RFI topic, but, I didn't see much there discussed with mobile RFI); if this is in the wrong topic, would an admin kindly move it over to the correct one.

I have a company vehicle which is a 2002 F-150 supercab pickup with the 4.8L V8 (for what the latter is worth).  It also has an aluminum topper on the bed.

I have my Yaesu FT-450 connected directly to the battery.  I have coax running to the very back of the topper, and the antenna mount is directly on the top-drivers side of the rear of the topper.

I get really nasty RFI, more so when I have a hamstick resonant on the band I'm tuning, and it's especially pronounced on 20M.  The noise also changes pitch with the increase in engine RPMs, and is REALLY noticeable when you let off the accelerator.

The noise goes away when I disconnect the antenna from the radio, so, I'm assuming it's not coming in through the power leads.

I have checked and verified the following:

Topper is grounded to the bed (did this myself)
Bed is grounded to the frame (came like this)
Cab is grounded to the frame (came like this)
Front panels are grounded to the frame (came like this)
Battery is grounded to cab (came like this)
Muffler is grounded to the frame (did this myself)

The grounds that I have done myself, I used the braid from scrap coax, flattened over a pipe.

I have tried to ground the radio's (-) lead about 4 inches from the rear of the radio directly to the cab; no change in noise (even though I'm sure the RFI isn't coming in through the power leads).

I can put just the tip of the PL-259 into the radio's antenna connector, and the noise is there.  I can touch the shield of the PL-259 to the inner part of the radio's antenna connector, and the noise is there.  The only time I can make contact with the antenna and radio with no noise, is if I just touch the shield to the threads of the radio's antenna connector without the center conductor touching anything, and with that, there's no basically no antenna/reception at all...

I have pulled the wires from the alternator to where the truck's just running off the battery; no change in noise.

I have put 2 ferrite choke cores on the lead from the alternator to the battery; no change in noise.

I have put 2 ferrite choke cores on the coax right at the antenna connection; no change in noise.

The noise doesn't appear to be the fuel pump; it doesn't have any noise when you turn the key on; only when the vehicle is running.

Where next?  Or, are these vehicles just inherently "noisy" and this is as good as it's gonna be?

BTW, there is absolutely NO way to even have the radio on with the noise blanker off; it's nothing but noise.

It's become an extremely frustrating issue that's about to make me quit running my rig mobile when I can't hear less than S9 signals over the RFI.

Help?
« Last Edit: September 07, 2010, 05:26:39 PM by Brian Spence » Logged
KL2GN
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Posts: 31




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« Reply #1 on: September 07, 2010, 05:54:24 PM »


Sorry to hear about your mobile noise issues....
A few questions...What type of mount are you using and how exactly do you have it mounted?
You said that you are using hamsticks? correct?

You say that the various pieces of the vehicle are grounded?  I have yet to see a factory vehicle that is appropriately "bonded" together.  How many places did you bond the topper to bed?  The bed to the frame? The frame to the cab? The cab to the frame? The hood to the frame?  The factory doesn't do a very good job of this.

What type of ferrites did you use? what mix? snap ons?

Be happy to help troubleshoot....need a little more info to get some thoughts.

73, Tim
KL2GN



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KE4DRN
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« Reply #2 on: September 07, 2010, 09:02:34 PM »

hi Brian,

the fuel pump will run a few seconds to pressurize the system,
then will stop until the engine starts running.

not sure if your model had the Ford fix for the fuel pump.

take a look at this link http://radioproshop.com/fordrfi.htm

73 james
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KL2GN
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Posts: 31




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« Reply #3 on: September 07, 2010, 10:27:23 PM »


Brian -

I was just reading over your post again and wanted to ask - Can you describe the noise any better?
Is it a whine? hiss? pulsing noise?  single distinct pulse?  2 or more pulses?

The 2 worst I have dealt with helping friends track noisy mobile setups were traced to the injectors in one truck and the other was alternator noise due to a ground loop in a car.

73, Tim
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K0BG
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« Reply #4 on: September 08, 2010, 06:54:04 AM »

Putting ferrite beads on DC power leads won't do any noise suppression, period! You could use a brute force filter, but if that f cured a problem, then something else in the installation is amiss.

The noise is probably the fuel pump, as Ford didn't start putting filters on as standard equipment until 2003, and the trucks didn't get them until 2005. You can still have one installed, but the price isn't cheap! You can do just as well by installing a ferrite bead on the power lead to the pump. This will require you to extend the lead long enough to get at least 8 turns on the core. Also, the ground lead from the pump to the frame on most model PUs, it over 4 feet long. That needs to be shortened. There is a TSB on this, and you can down load it from the web. If you can't find it, have your dealer print one out for you.

Depending on the production code the 2002 that you have may be either coil packs and wires, of COP (coil over plug) units. If it is the latter, there's not much you can do. If it is the former, new plugs and wires, are in order.

If you go to my web site, and look under Noise ID, there is an example of fuel pump noise.

Lastly, if the noise continues for 3 to 5 seconds after you switch off the ignition, it's the fuel pump. It runs until the oil pressure falls in order to purge the vapor canister.
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WK5H
Member

Posts: 111




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« Reply #5 on: September 08, 2010, 07:04:17 AM »


Sorry to hear about your mobile noise issues....
A few questions...What type of mount are you using and how exactly do you have it mounted?
You said that you are using hamsticks? correct?

The mount was put on by the person who had the vehicle before me (company vehicle), and he also is a ham.  It's a mount that's typically used for a CB antenna; 4 bolts mounted vertically to the back of the topper.

I say they're hamsticks, but, they're actually the ones from MFJ; for example, the 20M stick is this one:
http://www.mfjenterprises.com/Product.php?productid=MFJ-1620T

You say that the various pieces of the vehicle are grounded?  I have yet to see a factory vehicle that is appropriately "bonded" together.  How many places did you bond the topper to bed?  The bed to the frame? The frame to the cab? The cab to the frame? The hood to the frame?  The factory doesn't do a very good job of this.

The topper is bolted about every 2 ft with bolts to the bed of the truck.
The bed has about a 6awg wire bolted from the bed to the frame on the passenger side.
The cab has a fairly large strap on the passenger side under the door that grounds it to the frame.
The hood has ground straps from the hood to the cab at each hinge.

What type of ferrites did you use? what mix? snap ons?

The ferrites I used were the snap-on type from Radio Shack.  The exact ones are here:http://www.radioshack.com/product/index.jsp?productId=2103222

Be happy to help troubleshoot....need a little more info to get some thoughts.

73, Tim
KL2GN

Many thanks!




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WK5H
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Posts: 111




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« Reply #6 on: September 08, 2010, 07:09:32 AM »


Brian -

I was just reading over your post again and wanted to ask - Can you describe the noise any better?
Is it a whine? hiss? pulsing noise?  single distinct pulse?  2 or more pulses?

The 2 worst I have dealt with helping friends track noisy mobile setups were traced to the injectors in one truck and the other was alternator noise due to a ground loop in a car.

73, Tim

I'll get a recording of the noise today when I'm on the road, and put it up.  It's more of a whine/hiss.  I wouldn't say it's a pulse, unless it's a very very fast pulse.
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WK5H
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Posts: 111




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« Reply #7 on: September 08, 2010, 07:11:48 AM »

hi Brian,

the fuel pump will run a few seconds to pressurize the system,
then will stop until the engine starts running.

not sure if your model had the Ford fix for the fuel pump.

take a look at this link http://radioproshop.com/fordrfi.htm

73 james

I don't think it's the fuel pump; the sound files I've heard on the net that are described as fuel pumps don't sound much like the noises I'm having, but, I'll post up the noise that I'm having and maybe that will help.
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WK5H
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Posts: 111




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« Reply #8 on: September 08, 2010, 07:13:55 AM »

Depending on the production code the 2002 that you have may be either coil packs and wires, of COP (coil over plug) units. If it is the latter, there's not much you can do. If it is the former, new plugs and wires, are in order.

I do know for a fact that this vehicle has coil packs; one went out about a month ago, and had to be replaced.
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K0BG
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« Reply #9 on: September 08, 2010, 09:21:09 AM »

The ferrite beads from Radio Shack are all but worthless. They're an unknown mix, and a 6 turn core doesn't have any appreciable reactance until the frequency is over 100 MHz. The mix you want is Mix 31. The best price at the moment is from DX Engineering. A package of 5 of the 3/4 inch ID beads is $25 plus shipping. AES and HRO both sell them too. Remember the reactance is to the square of the turns, so a multiple turn bead is better than a bunch of one turn beads.

If it is a company vehicle, you're sort of stuck. As plugs age, their gap gets wider, which raises the voltage, and the RFI. Age also makes the wires leakier.

Post the noise someplace, and e-mail me the location. I'll let you know what I think it is.

Let's visit the fuel pump again. When you first turn on the ignition, the pump runs for about 3 to 5 seconds, and stops. Once the engine is running, the pump runs, but not continually. The percentage of run time is determined by the fuel needs of the engine. The cycle increases with engine speed, but not nearly at the rate the ignition RFI does. If it sounds like a hash which turns into a buzz at high RPM, then is probably ignition RFI. I have examples of both on my web site.

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WK5H
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Posts: 111




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« Reply #10 on: September 08, 2010, 03:03:36 PM »

I got some decent video with audio of what the noise is; more of a crackling noise, from what my ears tell me.

This one is where I am parked in a parking lot, turn on the key for a few seconds, then start the truck a couple of times.
http://www.youtube.com/watch?v=vF7vIh2kP48

This one is where I'm going down the road, then come to a complete stop and turn off the engine.
http://www.youtube.com/watch?v=x3mhRXKUQC8

BTW, my radio does NOT look this bad; youtube's compression instantly made my radio look like I drug it through a caliche pit...  And the radio also doesn't shake around like the video shows...  My hand holding my iPhone, however...
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KL2GN
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Posts: 31




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« Reply #11 on: September 09, 2010, 02:46:02 AM »


Brian-

Thanks for the response and posting the video clips.
If you were driving a diesel I would say it was injector/ignition noise.....but since your not.
I thought I heard a little bit of hash at the beginning...sounded like fuel pump but the rest of it sounds like ignition noise to me.

I'm sure Alan will have some thoughts on it, he has helped troubleshoot way more of these then I have.

73,
Tim
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WK5H
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Posts: 111




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« Reply #12 on: September 09, 2010, 08:06:27 PM »

Alan has given me some tips, and as soon as I get a chance, and the afternoon rain showers quit, I'm going to put em into production.

As soon as I get em done, I'll report back to let everyone know the changes.

Thanks again to all!
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K8KAS
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Posts: 569




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« Reply #13 on: September 17, 2010, 06:32:11 AM »

The worst noise generator on Ford products is their fuel pump period. The first thing I would do is get a filter on the pumps wires at the tank, I think ARRL has a lot of info on what it looks like, I believe Ford Parts as well offers one for their TDOT program avbl thru the dealers. I built 2 or 3 of these a few years ago but can't remember the values I used, but I can tell you the difference they made was day and night. Ferrite beads from Rat Shack are worthless I agree, and if you do use 31 type or 43 type from a good source it takes lots of them like 15 or 20 to see any change, 1 or 2 are just a waste of time. 73 Have Fun Denny K8KAS
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AA4PB
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« Reply #14 on: September 17, 2010, 09:32:20 AM »

Sounds like typical ignition noise from the spark plugs to me. Once you get rid of that you might find some fuel pump hash at a lower level.

What happens if you remove the antenna from the mount and just leave the coax and mount connected? If it is greatly reduced then its an indication that the antenna itself is picking up the noise.
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