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Author Topic: Alternator Whine  (Read 498 times)
KC0MLX
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Posts: 3




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« on: April 26, 2002, 12:55:26 PM »

I own a ICom 2100H.  I have it installed in a 1998 Ford F-250 4x4.  I had a mag mount, had no problem.

I decided to go permanant.  drilled a hole, and mounted an NMO on the roof.  Since then I get a whine.

I installed from Radio Shack, a 20 amp noise filter, it did not help.

I have been told its a ground loop somewhere?Huh?

I am new at this, any help!!!!!!!!    
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WB2WIK
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Posts: 20613




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« Reply #1 on: April 26, 2002, 04:57:55 PM »

How is the rig powered, i.e., are you using two separate wires (+ and -) to the battery, or are you using the vehicle chassis to complete the ground circuit?

Also: If you unplug the permanently mounted whip, now, and attach a mag mount, does the whine really disappear?  (Trying to rule out any possible "coincidence.")

Thanks,

Steve, WB2WIK/6
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KC0MLX
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Posts: 3




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« Reply #2 on: April 26, 2002, 05:04:58 PM »

I have the positive and negative wires directly to the battery.

as soon as I disconnect the antenna from the radio it goes away
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WB2WIK
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Posts: 20613




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« Reply #3 on: April 26, 2002, 05:29:27 PM »

Can you tell me what gauge wire you have connecting the rig to the battery?  

Sounds like possibly your coaxial cable shield is providing a lower resistance path to chassis ground than the (-) wire to the battery is, for some reason.

Have you cleaned & tightened the large strap that connects the (-) post of the battery to the engine block or chassis (or both)?

WB2WIK/6
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KC0MLX
Member

Posts: 3




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« Reply #4 on: April 26, 2002, 06:04:56 PM »

I am not sure what guage wire it is, its the cable that came with the radio.

also I have not cleaned the negative cable, looks clean.

also, I soldered the PL 259 to the end of the cable, and checked continuity, everything seemed fine, was wondering if my ground problem could be in the PL259??
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K0BG
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Posts: 9880


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« Reply #5 on: April 27, 2002, 09:36:24 AM »

Been there and done that! It is a ground loop, and sometimes they are hard to correct. Make yourself a few ground straps from some old coax and ground the cab to the frame and while you're at it, bond the bed, hood, tailgate and what ever else is bolted on. Get yourself to Radio Shack, or Amidon and buy a few of those clip-on ferrite beads and place them as close to the alternator as you can. In my case, it took three before the noise went away. Oh? welcome to amateur radio quirks 101!
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AA4PB
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Posts: 12905




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« Reply #6 on: June 06, 2002, 09:08:15 AM »

I just finished tracking down and correcting a very similar problem with my Alinco. With the radio squelched (no signal), the lower I set the volume control, the louder the alternator whine. The problem is that when the radio is grounded at more than one point in the vehicle (ground wire, radio mount, antenna shield), noise currents flow in the radio's negative power lead, through the PC board inside the radio (where the negative lead is connected)and through the case ground (also attached to the PC board inside the radio).

My solution was to run a bolt through a hole in the radio's heat sink to get a good case ground. I then attached both my ground lead and the radio's negative power lead to this bolt. This permits any alternator noise to flow directly through the case, bypassing the route through the PC board inside. The radio is now perfectly quiet.
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AA4PB
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Posts: 12905




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« Reply #7 on: June 06, 2002, 09:17:40 AM »

One interesting test that I performed was to take an 8-ohm headset and connect a couple of wire leads (one of them through an electrolytic capacitor just in case I contacted a hot lead by mistake). I connected one lead to the vehicle ground terminal near the battery and probed other ground points with the second lead. I could acutally hear the alternator whine in the headset when I touched the engine block or other points near the cab. I also heard the whine with the headset directly across the big ground wire between the battery negative and the engine block, indicating that the voltage drop in this cable is sufficient to permit the whine. This is a new vehicle with only 1000 miles on it. The connections, battery, and alternator are in good shape.
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