Fixing a Radio Noisy Prado 150 Diesel

The trouble with operating from a car is, modern cars with electronic systems can be RF noisy!

The diesel D4D engine in my Prado 150 series is no exception. With many sources of noise on the HF bands. From throttle noise to electronic injector noise, and base car background noise. Operating on some parts of the HF band with the codan in the car was almost impossible. Almost, until I spent some time to try and reduce the noise. And while not all the noise has gone, most of it has and the experience of HF in the car is MUCH better, and its still a work in progress, if you have other ideas or solutions, let me know!!

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Ferrite clip on cores.

After some research on the net and asking around, people suggest FERRITE CORE, SPLIT, 9.85MM, 225OHM Type 43 devices.

Initially i purchased some cores from jay car, and they did make a difference, but didn’t really FIX the problem, so I went in search of the recommended type and found these from Fair-rite at Element14, part no# 0443167251 , they are $1.49 each. Ive used around 15 on the car, and while I have no idea if any one is required, I’ve tried to clip them onto as many motor/control cables as I can find in the engine bay and the combined effort has really reduced the noise from the throttle/acceleration. Its not fully gone, with a slight clickly sound at 14Mhz, but its removed basically all of the noise at 3.6Mhz and 7Mhz. and made the higher bands much more useable.

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The left photo shows the cores on each Injector. The right photo on the injection control system.

I have also added them to throttle control and other engine electrical systems. This is a work in progress, I continue to add/change/move around the clips to find the optimal spot to solve this noise issue! Since the pics the locations have changed!..

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Core’s on throttle body and other motor systems. I keep moving them around trying to find the sweet spot!

Earthing.

In the car i run a codan NGT and a 9350 auto tune antenna. This antenna has an earthing strap that comes with it, and requiters a good car earth to work efficiently. I had earthed the antenna to the rear door of the car, and the body shell, and cross earthed these car 3 elements, the body and antenna were well connected. I have also earthed the codan Radio control body the body, and installed a Ferrite clip on the coax at the radio body, But in talking with people, the Prado uses rubber body / chassis and engine mounts. all three elements are not bonded. So this was the latest effort, and this has made the biggest difference. I purchased some earthing strap from vk3ajj radios.net.au and set about fixing the issue!

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Antenna earth strap connects to rear door bolts, and antenna bracket to rear door in alternate location

I started by running an earth strap from the rear exhaust to the chassis of the car, the rear exhaust hanger sits on a rubber bush and I have connected a earthing braid/strap form this hanger with the use of a stainless steel nose clamp. I gave the exhaust hanger a good scrub with a wire brush to ensure a good connection. The other end of this earthing strap connects to a Bolt that holds the rear diesel tank stone guard onto the chassis rail behind the rear right hand wheel. Seen in the right photo below. If i was better organised, I would have used some star washers where I connect this cable to produce the best possible connection, and I might retrofit these as I continue to tinker.

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Exhaust hanger to chassis earthing.

This bonded the exhaust and chassis, I needed another run to done these to the car bodywork. I contemplated my options and decided using another run from the exhaust hanger point to the rear door point I had earthed the antenna too. This required a separate run of braid, along the chassis and up behind the rear bumper to this door bolt point.

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Exhaust hanger to car body earthing.

The earthing of the chassis and exhaust has made the biggest difference. The car noise and throttle noise on the lower bands has dramatically improved, the Codan NGT shows a RX level as dBuV, and before the Ferrites, this would hover at the mid 55dBuV levels, with changes in noise on throttle application and driving. After the Ferrites were fitted, the noise would hover around 50dBuV level, and the noise form throttle and car usage was much less, but still annoying.

Now I have earthed the chassis and exhaust to the body/antenna. Noise is now in the 20-30dBuV range, depending on the frequency, and on 80/40m, no real decreeable throttle noise appears to exist. Some slight click noise at 14mhz under throttle, and gone on the higher bands.

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Engine on and stationary, noise on 7Mhz ~20dBuV

With the car switched off away from man made noise/power, i can see values in low single digits, so i haven’t completely fixed the noise level, but a change of +20dB is a HUGE improvement in noise levels while driving the car, and the noise generated while driving that could mask other operators/interfere with a conversation has pretty much gone!. I wonder if its also made the TX side better as the car is now a larger earth! only time and usage will tell!.

The process isn’t over, the earthing continues, next time I have some time to spare, I plan to earth the body, engine/exhaust and chassis to each other at the front end of the car also. A job for another day!

3 thoughts on “Fixing a Radio Noisy Prado 150 Diesel

  1. Hello, great post, I am just trying to do the exact same to my Patrol. Those ferrite cores are listed for $12.22, Where did u get urs from for $1.49 ?

    thanx.

    • from element 14, when i purchased them, they were MUCH cheaper……. the link i used is on that blog. i see they have gone up in price a LOT..

  2. I have done a lot of work with vehicle noise as well. Also had an old Prado which I go to be RFI quiet. Now a Nissan with no electronics. Vehicle noise 0dBV on NGT.

    Are you an Austravel Safety Net member.

    VK6TQ (7880)

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