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Author Topic: Alternator whine in older Dodge/Cummins  (Read 2349 times)

Posts: 1

« on: June 22, 2001, 01:10:04 PM »

This subject seems fairly common, but here goes again... I have a '91 Dodge Ram 250 pickup I have used mobile casually in the past with several Kenwood radios - a 440,450 and 570 - and am now more permanently installed with an Icon 706 MKIIG - also using Hamstick monoband antennas primarily on 40 and 20 meters. As in the past, I have an S5 alternator whine that rises and falls with engine speed, regardless of whether the truck is in motion or not - the noise goes away completely when engine is turned off, and also (pay attention now!) when antenna is *disconnected*! It seems to me that the noise is RADIATED noise rather than CONDUCTED noise as from power leads. My setup is well grounded at the radio and antenna mounts in the bed of the truck, and substantial power leads for the radio go directly to the truck battery. The older Dodge/Cummins (pay attention now!) have NO computers on board, engine operation is purely mechanical, the ONLY 'puter is the rear brake ABS system - and as I stated, the noise is directly related to ENGINE speed, NOT vehicle speed.

I assume I need RF bypassing at the alternator - WHERE can I get these capacitors/filters, and specific recommendations as to best installation methods and cautions? My alternator sells for well over $200 - I sure don't wanna screw it up!

Posts: 984

« Reply #1 on: June 24, 2001, 04:46:52 PM »

Well you can do three things.
1: Go to Radio Shack and get their 20 Amp bypass kits for attachment between battery and ground to bleed that noise off the electrical system.  
2: You can also see if putting some belt lubricant on the drive belts to the alternator and water pump reduces the noise. They do that while running and are more prone to doing that if they are older belts that have had time to stiffen and dry out. At the same time be sure all bearing are also lubed in the areas that are driven by the belts.
3: Ground all body parts together using some braid taken from old coax. That means the hood, doors, muffler and pipe, pickup bed to the body and frame and any other part that could "float" and generate or allow RF to reach your antenna.
Do that and you should eliminate nearly all the RF causing you problems. Be sure to tighten all electrical connections while you are at it. Any connection that is not tight or partially corroded acts as a detector for RF in the spectrum you would prefer not to hear. Similar to old crystal radios. Good luck. Hope this helps.

Posts: 28

« Reply #2 on: July 04, 2001, 12:01:37 PM »

you can obtain a hi-amperage noise filter from k5bug--"the texas bugcatcher"---he has a web-site  with his products listed---also---the larger truck stops--will usually have this type of device-as "some" truck drivers "thiMk" its o.k. to run a kw with their cb raydiddo----somebody needs to tell them that those antennas  are built for about 10 watts of RF----- good luck , kd5ir
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