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Help with car radio install


bkuhr
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Looking for suggestions to help eliminate FM tuner interference

 

2005 Dodge Dakota. Installed Kenwood KDC-BT365U. Also cell phone holder installed near radio head.

I had very bad FM tuner interference after 1st install, to the point that auto tuning could not find any channels, and manual tuning to known good channels finds the stations but very broken and noisy.

 

I opened the dash back up thinking I had damaged the antenna connector.( When I removed connector from the OE radio, I had to pry it out). I did not see any damage to the antenna connector or the dodge to Motorola antenna adapter. Even so, I cut off the dodge connector from the coax, and directly installed a replacement Motorola connector on the coax for a direct fit without adapter to the new Kenwood.

 

Putting dash back together and had the same issue. Taking it back apart again while the radio was playing, I found the issue. The cell phone, when plugged up to the charger, is causing the problem. This problem did not exist with the OE radio/cell in the same configuration.

 

I found I still have the interference even with the cell in the lap, so relocation is not a practical option. I also tried 2 different cells, HTC and Note5, and same issue.

 

After much experimentation, I have reduce to problem by moving the phone charger from the dash power receptacle to the rear of center counsel power receptacle, leaving the phone at the original mount location near the radio head. Still some interference. I even wrapped aluminum foil under the removable face plate to the radio chassis attempting to provide front shielding. Call to BestBuy and tech stated that all after market radios have less shielding than OE radios. No sure that I believe this statement. Call to Crutchfield did not offer any suggestions.

 

I am not sure what else I can try. I am very suspicious that the problem is primarily due to this specific model, or maybe just this specific serial number of the Kenwood radio, but I am leery to return it to the store, purchase another radio of same or different type/brand and have the same issue.

 

I am also considering getting on of those cheap antenna "pre-amp's" with the thought that the higher power antenna signal into the radio will overpower the interference it is experiencing, but everyone I speak with says these things are just junk, and don't really do anything.

 

Any ideas or suggestions of a different radio to try.

 

The Dakota OE is 1-1/2 DIN, although I have read that some have fitted a 2 DIN with custom cutting, I am not sure I want to cut the dash up, but may consider it. I currently have a 1 DIN dash adapter that fits good. Feature Requirement is FM, CD, USB/AUX, Bluetooth Hands-free for at least 1 phone. Additional would like would be BT for 2 phones, GPS NAV, backup camera..

kenwood radio.jpg

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Interesting problem:

 

You could try to augment the shielding by making like a Faraday cage around the radio...nothing more than a metal type shield that covers the non-seen outside of the radio chassis and ground that cage to radio chassis and truck ground. You can try and add a metal shield plate behind the phone between the phone and mount...and find a way to ground that...or maybe not...just the shield plate might work. The idea here is to capture the spurious signals before the front end of the radio does.

 

Other than that....I've put all sorts of radios into vehicles and only ran into this type problem once: In a 1972 Open GT. Had to build a cage around the instrument panel to isolate all the ignition crap and such that was giving us fits and ground it. We used a fine mesh chicken wire looking stuff made out of copper. Worked.

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Thanks Video,

I have already tried shielding. I wrapped foil around chassis and front end behind removable faceplate. When I completely wrapped the cell, (ungrounded) it made the problem 10x worse.

 

So far the best solution has been using the rear power port, but looking for recommendation of a better radio. Looking at specs for the Kenwood, it has FM sensitivity of 8.2dbf. Unless this radio is defective it is low enough there should not be a issue. A preamp would probably overload the front end. Maybe an attenuator would make it less sensitive to the cell interference, but then likely not pick up FM. I'm stuck

kenwood radio foil.jpg

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this is usually more for AM issues, but go grab yourself a ferrite (ie: iron) bead (the split type that clips shut) and put a wrap of the power cord in it. You want the bead as close to the power source (in this case, the adapter) as possible. Keep adding wraps until it either goes away or the ferrite can't hold any more wraps. You're probably going to at least have 2-3 wraps before it does much of anything.

 

Like so:

 

http://www.cisco.com/c/dam/en/us/td/i/300001-400000/340001-350000/347001-348000/347546.eps/_jcr_content/renditions/347546.jpg

 

What you are doing is making and RF choke on the power line.

 

It may work, it may not.

 

I've fixed lots of AM static interference problems this way. Often, the power cord on a DC device will produce RF, acting like a transmitting antenna. I've never had a problem with it adversely effecting FM (although I have heard it faintly), but it's worth a try.

 

And if it doesn't work, you're only out a couple bucks. Ferrite beads are cheap....

Edited by Great White
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Thanks Great White. A suggestion I had not thought of. And I have some ferrite beads.....somewhere.

Also of note, when I moved to the rear power outlet, I ended up using a long (15') USB cable, and the slack coiled up near the rear power outlet. The coil may be part of the reason it was better at the rear outlet

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Thanks Great White. A suggestion I had not thought of. And I have some ferrite beads.....somewhere.

Also of note, when I moved to the rear power outlet, I ended up using a long (15') USB cable, and the slack coiled up near the rear power outlet. The coil may be part of the reason it was better at the rear outlet

 

Yup. A coiled line is also a form of RF choke.

 

Not as effective on a DC power line, but it will still has a choking effect.

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