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Author Topic: Ignition/engine noise on a 95 Toyota 4runner  (Read 1129 times)
SOON_TO_BE_HAM
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Posts: 3




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« on: July 17, 2001, 08:36:06 AM »

I am taking my Tech exam next week. So I got excited and decided to pickup my first rig and install it over the weekend. I decided on an ICOM-207H dualband.  I got the remote head wire and mounted the unit under the drivers seat, with the display to the left of the steering column. I also installed a Larsen glass mount dualband antenna.

I was worried about noise in the electrical system so I installed a RadioShack 20AMP noise filter on the power lead to the battery. I used 12 guage wire all around, ran both the (+) & (-) directly to the battery, grounded the ICOM chassis to the body, and double checked the trucks grounding.

So I fired up the radio on 2m to listen in. If I am getting a strong signal there is no noise and it is clear as a bell. As I started to scan through freqs I get a popping sound with a whinning sound in the background.  This noise gets softer and louder depending on how much gas I give the truck. If I turn the truck off and just listen in there is no noise at all.

Is this the fuel pump? Ignition? Should I ground the doors, exhaust, etc with wire?

Thanks for the help!
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KC0GUK
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Posts: 15




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« Reply #1 on: July 17, 2001, 09:04:24 AM »

Here is an article that fits your vehicle.  You may not like what you read on eliminating the noise.  I am
still trying with a 98 Ford F150 with no luck.

http://www.k2bj.com/Pages/Noise/articles/downs.pdf

73
Chuck
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WB2WIK
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Posts: 20547




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« Reply #2 on: July 17, 2001, 10:56:56 AM »

Regardless of the noise generated by your vehicle, FM is a strong-signal mode and FM receivers have enormous noise rejection; it's the primary reason for the mode's existence.  

Do you hear the popping and whining when tuned to an actual signal, or just between signals on vacant channels?  If only on vacant channels, this is an awfully big "who cares?" and I certainly wouldn't spend ten seconds investigating it.  If you hear vehicle-induced noise that varies with engine speed when tuned to an actual signal that you can otherwise copy fine, that does sound like a problem.  It may even be a problem with the radio itself.

Lots of tests you can run:

1.  Disconnect the antenna, and see what impact that has on the noise.  If all noise is completely eliminated when the antenna's disconnected, then it's all coming down the coax from the antenna.  This is important to know.

2.  With the rig on but the truck "off," turn the key to the "on" position but without starting the engine.  Do you hear the popping or clicking (usually for 5 seconds or so)?  If so, it's the fuel pump, not the ignition system.  

3.  If it turns out to be purely ignition noise, first thing I usually do is pull the vehicle into a garage that has doors that can be completely closed, or wait until nightfall when it's quite dark outside, pop the engine hood, start the engine and look carefully for any visible sparking.  If you see any sparking anywhere, that's likely to be the source of the noise.  Could be a bad or leaky wire, plug connector, lots of things.  I've solved an awful lot of problems using the "search in the dark" method.

4.  If your ignition cabling is more than two years old, it might be time to replace all the HV cables with new ones.

5.  If, no matter what you do, the noise is still bothersome and it's not some quirk in the radio itself, you might experiment with other antenna locations.  Unfortunately, motor vehicles are not all metal construction these days and with all the unshielded polymers used, strong noise fields can set up almost anywhere -- however, I've often found that simply moving the antenna to another location, found experimentally by using a "mag mount," solves noise problems.

6.  If all else fails, you might try temporarily wiring in a friend's rig in place of yours, and see if that works any better.  You might also try re-attaching the front panel to your rig, elminating the long cabling between the panel and the rig, which, unless it's 100% optical fibre (I doubt it), can easily pick up noise.

In general, FM receivers have terrific noise immunity, but that immunity is based on reception of strong signals.  Since FM is a "strong signal" mode and it's impossible to copy weak signals via FM detection, this is usually just fine.  AM receivers (including SSB, CW, etc -- anything using linear detection) have far less noise immunity and are normally plagued with all sorts of noise problems when used "mobile."  It's rather unusual to have noise problems with FM gear.

73 de Steve WB2WIK/6
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SOON_TO_BE_HAM
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Posts: 3




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« Reply #3 on: July 17, 2001, 01:00:34 PM »

The noise does happen when I am recieving "weak" signal. I would say S1 to S7 I recieve the popping noise.  If I sit a couple miles from a repeater and listen in it is clear as a bell.  I tried disconnecting the antenna, same noise. I tried listening for the fuel pump no noise there.

At my first attempt to install the rig I connected the radio to the trucks internal fuse box.  I jumped power from a 20A fuse and ran that to the radio. This was fine for listening, but after reading some posting and other mobile articles it was suggested that I wire directly to the battery for the power needed for transmission.  While wired to the fuse box the radio did not experience this noise.

From the info you guys have given me it sounds like it is coming from the ignition system.  I will try the in the dark trick and see if I can see any sparking.

Would it make sense to try grounding the rig inside the cab? Rather than running a ground all the way to the battery?

Thanks for all the help!!! I really appreciate it. I want to be clear as a bell once I get my license.
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WB2WIK
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Posts: 20547




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« Reply #4 on: July 18, 2001, 11:11:59 AM »

Did you try the test where you disconnect the antenna and see if the noise is still there?  You didn't answer that one.

Sounds like your routing the DC power cable past the engine helped create the problem, since it wasn't there (or maybe you didn't notice it!) previously.  That can happen.  Re-routing the DC power cable to push it as far away from ignition components as possible can help.  I usually route my mobile power cable to the battery along the edges of the engine compartment, bundling it in with things like the windshield washer hose, etc (never near things that get hot, or any ignition system components).  This can require several extra feet of cable -- but I use #8 stranded cable, so a few extra feet doesn't hurt.

Keep trying!  Adding a ground directly to the rig's chassis might help, shouldn't hurt.  It's a good experiment.

73 de Steve WB2WIK/6
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SOON_TO_BE_HAM
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Posts: 3




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« Reply #5 on: July 19, 2001, 08:33:47 AM »

Well half the battle is over. The rig is now getting noise free clean power. I added grounds to all body parts connecting them all to a central point under the hood. I add a chassis ground to the rig under the drivers seat. I used some belt dressing to tame the alternator whine. This got rid of some of the noise. Now I can hear what sounds like ignition noise being radiated into the antenna. I disconnected the antenna and rev'd the engine alittle. No noise at all nice and clean. Soon as I put the antenna back on the popping started again.

How do I get rid of this noise? Do I need to reposition the antenna?  The coax runs from the right rear of the truck to the rear passenger seat and then crosses the vehicle and goes up under the driver's seat to the rig.

Thanks for the help!! I am almost there.
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WB2WIK
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Posts: 20547




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« Reply #6 on: July 19, 2001, 01:47:41 PM »

Glad to hear you're making progress.

The glass-mount antennas can be more prone to picking up ignition noise, simply because they are "floating" and not securely grounded anywhere.  

What I'd do (and what I've done, many times!) is disconnect the glass mount antenna's coax at the rig, and try using a "mag mount" whip antenna with its supplied cable, mounting the antenna temporarily at various locations all over the vehicle to see if you can find a very quiet spot for it (no ignition noise).

In vehicles that are all-metal construction (entire shell is sheet metal), the obvious spot, which not only works best but also typically receives the least amount of ignition noise, is right in the center of the roof.  At that location, the whip is completely shielded from the car's ignition system, as there is horizontal, shielding sheet metal all the way around it.  Perfect!  When the shell is not all-metal construction, the "best" location is not so obvious.

73 & keep up the good work!

Steve WB2WIK/6
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KB1HAG
Member

Posts: 4




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« Reply #7 on: July 20, 2001, 09:26:40 AM »

SOON_TO_BE_HAM is now KB1HAG.

So I decided to ditch the glass mount. Gonna drill some holes at the back and mount a 5/8 wave antenna for 2m & cut down a 2m 1/4 wave antenna for use on 70cm.

Hopefully a well grounded antenna will tame down the radiated RFI.

Jeff
KB1HAG
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