| Author |
Message |
    
Dcobb
| | Posted on Monday, July 08, 2002 - 7:51 am: | 
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Let me ask all you wizards out there a question. I'm running Cobra and Midland CBs in my vehicles (an S-10 truck and a Pontiac car) with a Wilson 500 mag antenna and I'm picking up engine noise, specifically a type of engine noise (maybe a whine?) that increases with engine speed. The radios use cigarette lighter plugs for power.
I bought a Radio Shack 10-amp noise filter and installed it in the power and ground lines (between the plug and the unit). No luck in reducing the noise. I assume the lighter plugs are properly grounded and for portability prefer not to wire directly to the battery.
What suggestions do you have? |
bruce
| | Posted on Monday, July 08, 2002 - 10:46 am: |
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Back 30 years ago i had a HR-6 regency 6 meter fm rig NOTHING worked except going to the battery. Go directly to the battery but FUSE THE WIRE WITH A WIRE ON THE BATTERY SIDE OF THE FUSE TO SHORT TO TOUCH GROUND...... trust me on this one.... TRUSY ME! |
Dcobb
| | Posted on Monday, July 08, 2002 - 11:12 am: |
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I've been doing some reading on the subject and it seems that almost everybody suggests going directly to the vehicle battery - even some of the manufacturers. That complicates things somewhat, but I can probably survive. Several people have suggested fusing both the hot and negative sides, too.
I need to do some testing to see if my noise source is mostly conducted through the power lines or if it's radiated through the antenna. |
307
| | Posted on Monday, July 08, 2002 - 12:20 pm: |
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Going directly to the battery positive and negative should drastically reduce the noise because the battery acts just like a filter. If it is conducted through the antenna , un-plugging it will eliminate the noise when you terminate the connector on the radio with a dummy load.
307 |
jyd
| | Posted on Monday, July 08, 2002 - 12:47 pm: |
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i went staight to the battery and still got noise |
Triplecguy
| | Posted on Monday, July 08, 2002 - 12:58 pm: |
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Hey bruce, please read what you wrote and re state it I can not understand it. Where do we put the wire from the battery to ground? This sounds like a direct short unless I am missing something.
Dan |
bruce
| | Posted on Monday, July 08, 2002 - 2:04 pm: |
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ok again you should FUSE the hot wire (+) just as it leaves the battery and for safty the wire length should be ( before the fuse ) too short to reach any ground. I cooked a battery when the wire broke loose from the fuse block and found a ground.
Hey Dan like this better! LOL
bruce |
Dcobb
| | Posted on Monday, July 08, 2002 - 3:46 pm: |
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After a little more testing, I think the radio is part of the puzzle. My Cobra is a low-cost handheld model and seems to be more susceptible to the interference, even with an external antenna. The Midland is a 'regular' radio and seems to be pretty clear of the noise. |
Tech181
| | Posted on Monday, July 08, 2002 - 4:28 pm: |
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The coax on a Wilson antenna is 18 feet long, which is a 1/4 wavelength of the frequencies we operate on. This is very much a factor is receiving outside interference, including alternator noise. I may be wrong, but I believe the coax on a Wilson acts somewhat like a counterpoise. The coax is picking up a significant amount of noise and "transmitting" it right into your receiver.
Steve
Tech181
Tech181@copperelectronics.com
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Tech181
| | Posted on Monday, July 08, 2002 - 4:29 pm: |
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Correction...18 feet is 1/2 wave. Even more efficient of a receiver than a 1/4 wave.
Steve
Tech181
Tech181@copperelectronics.com |
409
| | Posted on Monday, July 08, 2002 - 5:11 pm: |
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If you have a "whine" which changes with RPM,then it's alternator noise. Some of our local cops have the same problem and you can hear it in the TX on their radios. You might try a filter that connects directly to the alternator. |
Bigbob
| | Posted on Monday, July 08, 2002 - 7:28 pm: |
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Why don't we all go to steam and use carbide lights and a giant battery for the radio,no more electrical noise. |
