excessive noise in radio on 40 meters

[msimon]

I have a 2005 pete with a c-15 cat. My setup is a Yaesu 897d into a Hi-Q 5-80. Now there is no noise when the engine is off and no noise with the key cycled to start. That means the computer on the engine is on and most gauges are operating. The noise begins when the motor is running and the higher the rpm the noisier it gets. I have braided grounds to the frame from the alternator and exhaust. the doors are grounded to the cab and cab is grounded to the frame. The radio chassis is also grounded to the cab as is the ground from the antenna. It is very noisy on 40 and tolerable on 75. Everywhere else is fine,very small amount of noise. Has anyone had this issue and figured out what the problem is. I almost think its injectors but haven't found anything to support that theory from cat or anywhere else. Could someone point me in the direction on where to find some answers. Thanks in advance from Mike in Winnie,Texas KC5CST

[N9GQR]

Mike, sorry for the slow response. I believe you have a Leese-Neville alternator? Correct me if I'm wrong. From what I remember the fix is a simple one and inexpensive. Install (3) .01mf capacitors and daisy chain them from the POS to NEG on the Alternator, then NEG to the Frame's Ground then the Frame's Ground to POS.

[K6TEX]

All of your noise is coming from the left side of your engine where the truck's ECM harness goes up to the injectors. We have cured this problem many times by just shielding the wires then grounding the shield. We weren't able to find braid large enough around, so we went to "Hobby Lobby" and bought some copper sheets (wear gloves, this stuff will cut you up). The sheets are regular paper size, wrap them around the bundle beginning at the bottom (make sure that no sharp edges can cut into you wires in the harness). Crimp the sheets together with crimpers so that there is a good electrical contact, then ground it to the frame.

Voila... No more noise!