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Jim's Ground Rules:
"My responses will be based on information from the ARRL Handbook and the ARRL Antenna book. The information will be of practical use and will not contain deep theory. If anyone wants to explore more technical information e-mail me direct: speerjames@bellsouth.net and I will try to point you in the right direction. If you don't understand or disagree with information posted, contact me directly and I will attempt to clarify the info or correct any errors. Any errors will then be corrected on the website."

 



Question: I have an HF rig in a diesel pickup, and the electric noise made by the fuel injectors is loud, especially on 40 meters...like an S-9. Diesel injectors are powered by a step up process that gives them 120 volts....as you know, there is no "ignition" system on a diesel as such. I can unscrew the antenna and the noise goes away. My question is, should I try something like ferrite beads on the electric lines leading to the injectors?



Answer:
Half the fun of going mobile is getting the noise down to a low roar. You have already determined one thing when you removed the antenna and the noise went away. This indicates the RFI is radiated and not coming through the wiring. Make sure that your hood is grounded. Sometimes the factory system isn't enough for communication type radio. You may have to run a braid (at least 1 in wide) from the hood (near the hinge) to the chassis. Keep it short. That is a good first try because some sort of shielding (more complicated) would probably be next.

Stay Tuned......

*ED. NOTE: Under the advisement of our Technical Guru, I visited a website that had to do with the noise that is described above. The long and short of it said to ground not only the hood, but ground everything. So, I did like the article said: I grounded the cab, which "floats" on rubber insulators, to the bed, which is bolted directly to the frame, via a braided flat cable. Ditto on the hood, ditto on the exhaust system. That also rides on rubber insulators, and acts as a big antenna! After all that, no luck...still the same noise. I got to looking at the way I have the antennas mounted...on a bar across the bed. It's bolted to the top of the bed, but..... what the heck, I'll re-ground that too. VOILA! Noise gone! Just for grins, I un-did one of the previous grounds, and the noise came back. The moral of the story: Ground, ground, GROUND!

'73

Jim WB4FWO

 

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