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Old 04-14-2017, 2:46 PM
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Default 2015 Tahoe RX Noise when engine is started

I installed a Amateur Dual Band Radio in my 2015 Chevy Tahoe. Antenna is a NMO mount drilled into the roof (It has a good ground). Power is ran directly from battery. My Radio ground is to the body floor only about a 16" run.

When I turn on the radio with the engine off, my RX signal meter (only on VHF Channel) shows nothing, full quiet, but as soon as I start the engine, my signal meter practically pins to the max.

I tried another antenna with the same results, and also get the same results If I connect both antennas to a Mag Mount.

I have no whining noise, just RX Noise (see below video)

Radio: Icom 2730A
Antenna's Tested: Larson NMO-2/70B Black and Diamond NR-72BNMO

Where should I start looking to get rid of this noise?
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Old 04-14-2017, 2:51 PM
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https://youtu.be/UXyhtZg4Je8
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Old 04-14-2017, 2:57 PM
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Is it on just one frequency?

Maybe an accessory is causing it. I had a 12V to USB power adapter that created havoc on 146.52 plus or minus a wide swath.

Have you tried a different radio in the same application? Same radio in another vehicle?
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Old 04-14-2017, 3:02 PM
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it happens on any VHF frequency I turn to, when switched to a UHF freq, it goes away. I have another 2730A that does the same thing when plugged into the car.

no usb adapters
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Old 04-14-2017, 3:29 PM
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Boy, that's as bad as I've ever seen it. I'd guess it's RFI being generated in the vehicle and the antenna is picking it up. You can disconnect the antenna from the back of the radio and see if it diminishes or goes away completely. That would confirm.

Usually these days those cheap car chargers for cell phones are highly suspect. If you do not have any plugged in, do you have an AC outlet in the truck? The inverters can get quite noisy also.
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Old 04-14-2017, 3:36 PM
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If I unplug the antenna, the signal goes away
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Old 04-14-2017, 4:04 PM
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I FOUND THE CULPRIT !!!

It was a 12v to USB adapter I had under my dash to power up my Dashcam.

https://youtu.be/FUZJYqIz7Hk
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Old 04-14-2017, 4:10 PM
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Quote:
Originally Posted by fdnyfish View Post
I FOUND THE CULPRIT !!!



It was a 12v to USB adapter I had under my dash to power up my Dashcam.



https://youtu.be/FUZJYqIz7Hk


Awesome!


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Old 04-14-2017, 4:37 PM
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Nice work!
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Old 04-15-2017, 4:15 PM
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Yep, those will do it.

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Old 04-15-2017, 9:24 PM
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Yep, welcome to the world of RFI. This isn't limited to automotive scenarios either. It's a HUGE issue everywhere.
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