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Interference coming from head unit in Jeep


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#1 SkylinesSuck

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Posted 06 April 2021 - 07:07 PM

I noticed some constant noise breaking squelch on channel 17 with my old MXT275. Didn't think much of it. I recently swapped it out for a KG1000 and noticed it's receiving interference on several channels, worst on 17. It makes the rx light blink constantly without breaking squelch on some channels, and actually registers on the rx meter and breaks squelch on others. Strangely it even stops me from transmitting frequently, even though I have busy channel lockout disabled. I have narrowed it down to my double din wireless Android auto head unit. If I turn it off, interference disappears. Even when it's on but not putting out music, even with the sub off, even with the wifi turned off, it happens, even just in standby displaying the time.

I have grounded the piss out of the KG1000 to the body AND frame. I have installed literally 20 snap of ferrite beads of varying sizes (got an assortment for cheap on Amazon) on both the KG1000 as well as the head unit. I have also bonded the hood, body, exhaust, and frame. This interference happens even just in accessory with the engine off. I ran power cables for the KG1000 directly to the battery through an open window just to trouble shoot. No change.

Clearly the head unit is putting out some kind of interference. I double checked it's ground, but maybe it needs more? Any ideas?

I'm not having his luck with my radios lately. At least I have good swr on this one lol (1.3).

#2 mbrun

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Posted 06 April 2021 - 08:22 PM

Pardon my ignorance. For clarity, when you refer to head unit, are you referring to the removable, remotely installable, control panel that comes with the KG-1000, or are you referring to some attribute of the Jeep?

Michael
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Michael

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#3 SkylinesSuck

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Posted 06 April 2021 - 09:04 PM

Sorry, the car stereo.

#4 serrasalmus

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Posted 06 April 2021 - 09:42 PM

have u shut off the blue tooth also? is it sat radio? with it being gone with a hard off then its def something in the head unit, could always try the tin hat method, could it be the digital fm receiver maybe try wrapping the antenna cable in said tin foil hat where the adapter more then likely is to go from a jeep to standard fm antenna. if your using the stock radio ground, why not try moving it to a good new location just to see the results? just throwing out ideas....good or bad is your call.........i take no responsibility if u blow up your jeep, blame that on the next door neighbors 


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#5 WPXM352

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Posted 07 April 2021 - 06:59 AM

Does the head unit have a USB charging point?

Sent from my SM-T350 using Tapatalk
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#6 SkylinesSuck

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Posted 07 April 2021 - 08:42 AM

Does the head unit have a USB charging point?

Sent from my SM-T350 using Tapatalk


Yes! Two auxiliary cable inputs. Didn't even think of that. Maybe unplug them or wrap them in foil? Is USB notorious for interference?

#7 tweiss3

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Posted 07 April 2021 - 08:53 AM

Jeeps/Dodge in general are notorious excessive RFI across the board.

 

Yes, cheap power transformers for usb power do usually cause RFI as well.



#8 Lscott

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Posted 07 April 2021 - 09:36 AM

Sorry, the car stereo.

If in fact the noise is coming from the car stereo it's likely radiating from the wires between the speaker output and the speakers. Many new car stereos use Class D power amplifiers. To make it simple its a switching type circuit operating at high frequency, HUGE noise generators if not filtered. If the filtering is insufficient on the amp's output you can try putting your clamp on ferrites on the speaker wires right at the point where they exit the amplifier. You might even have to shield those wires and ground the shield right at the stereo.

 

https://www.analogic...hed-mode-sound/

 

The communications between the head unit and the main body is also likely using a fast serial communication protocol. One common protocol used extensively in automotive settings is the CAN bus. Those signals may also be a source of noise radiation and might need those clamp on ferrites too.

 

https://en.wikipedia.org/wiki/CAN_bus



#9 OldRadioGuy

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Posted 07 April 2021 - 10:44 AM

Make sure you have a ferrite or two on ALL wires connected to the car stereo.

Especially the radio antenna cable.

I'm sure it's not easy to access these things but you have to do all the wires or it won't help.

 

Vince


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#10 Mikeam

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Posted 07 April 2021 - 11:16 AM

Sorry posted in wrong thread!



#11 SkylinesSuck

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Posted 07 April 2021 - 12:23 PM

Make sure you have a ferrite or two on ALL wires connected to the car stereo.
Especially the radio antenna cable.
I'm sure it's not easy to access these things but you have to do all the wires or it won't help.

Vince


I didn't know that, thanks. Just ordered another assorted pack of 20. I only had them on the power wires before.

#12 SkylinesSuck

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Posted 07 April 2021 - 12:25 PM

If in fact the noise is coming from the car stereo it's likely radiating from the wires between the speaker output and the speakers. Many new car stereos use Class D power amplifiers. To make it simple its a switching type circuit operating at high frequency, HUGE noise generators if not filtered. If the filtering is insufficient on the amp's output you can try putting your clamp on ferrites on the speaker wires right at the point where they exit the amplifier. You might even have to shield those wires and ground the shield right at the stereo.

https://www.analogic...hed-mode-sound/

The communications between the head unit and the main body is also likely using a fast serial communication protocol. One common protocol used extensively in automotive settings is the CAN bus. Those signals may also be a source of noise radiation and might need those clamp on ferrites too.

https://en.wikipedia.org/wiki/CAN_bus


No CAN bus for me. 1998 ftw ☺️ I will make sure to get chokes on the speaker wires.

#13 kb2ztx

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Posted 07 April 2021 - 01:11 PM

I have no issues in the JT or JK. I assume this is an aftermarket head unit ? If you know its the radio may not be alot you can do.



#14 SkylinesSuck

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Posted 07 April 2021 - 02:15 PM

It is an aftermarket Pioneer wireless Android auto head unit.

Interesting twist I just noticed--if I remove the antenna, no more noise. Maybe it's not line noise then?

#15 SkylinesSuck

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Posted 07 April 2021 - 02:17 PM

And by remove the antenna I mean unscrewing the entire antenna off of it's nmo mount outside the vehicle.

#16 tweiss3

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Posted 07 April 2021 - 02:21 PM

And by remove the antenna I mean unscrewing the entire antenna off of it's nmo mount outside the vehicle.

 

Well, that just makes the GMRS radio deaf.

 

How close is this antenna to the FM antenna? What antenna are you using for GMRS? What is the model number for the Pioneer unit? I wonder if there is feedback up the FM antenna of some kind. I'd be interested to do some research on the model.



#17 SkylinesSuck

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Posted 07 April 2021 - 02:31 PM

Pioneer AVH-W4400NEX and I just swapped out my Midland MXTA26 5/8 wave for a Larsen NMO450CHW 1/2 wave. The FM antenna is at the front of the Jeep, GMRS is at the rear corner. Another thing I just tried was too see if I had any issues with me CB and I do not.

#18 tweiss3

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Posted 07 April 2021 - 03:18 PM

It appears that radio has a iDatalink which is a CAN bus link to the OEM body controls and information. See if you can turn that off completely.



#19 SkylinesSuck

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Posted 07 April 2021 - 04:08 PM

I will look in to it. It's not hooked up to anything though because not CAN bus, but I'll see if I can turn it off.

#20 OldRadioGuy

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Posted 08 April 2021 - 10:12 AM

See what happens if you reconnect the GMRS antenna but disconnect the car stereo antenna.

It's very possible the stereo is radiating junk from its antenna.

 

If it's common mode radiation (which is likely) a ferrite on the stereo antenna coax will help.

 

This stuff can be very difficult to track down.

The car stereo is probably not even violating any RFI standards.

It's just so close that it doesn't take much.

 

Vince






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