Interference coming from head unit in Jeep

[SkylinesSuck]

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).

[mbrun]

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

WRHS965

KE8PLM

[SkylinesSuck]

Sorry, the car stereo.

[serrasalmus]

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 

[JLeikhim]

Does the head unit have a USB charging point?

 

Sent from my SM-T350 using Tapatalk

[SkylinesSuck]

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?

[tweiss3]

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

 

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

[Lscott]

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.analogictips.com/class-d-amplifiers-for-high-efficiency-switched-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

[OldRadioGuy]

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

[Mikeam]

Sorry posted in wrong thread!

[SkylinesSuck]

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.

[SkylinesSuck]

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.analogictips.com/class-d-amplifiers-for-high-efficiency-switched-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.

[gortex2]

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.

[SkylinesSuck]

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?

[SkylinesSuck]

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

[tweiss3]

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.

[SkylinesSuck]

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.

[tweiss3]

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.

[SkylinesSuck]

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.

[OldRadioGuy]

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

[SkylinesSuck]

Will do. Ferrites show up today so I'll mess with it tomorrow morning before work.

[tweiss3]

If it is a common mode RF, all the grounding you did of the radio may be feeding RF into the chassis. 

[SkylinesSuck]

I just tried removing the factory fm stereo antenna. No effect.

[SkylinesSuck]

Just for my understanding of principals here, wouldn't disconnecting the antenna and not receiving any interference point towards the interference coming in through the antenna i.e. broadcast interference and tell me it's not something coming through the power cables? I mean, no amount of grounding the radio out ferrite beads on the radio power wires will help, right? It's all about either filtering what the antenna receives or stopping the broadcast interference at it's source, right?

 

The antenna wire is not run anywhere even close to the head unit btw.

[tweiss3]

No, removing the antenna just means the radio is receiving the signal, and it's not due to a direct contact on the coax. 

 

If you had a TinySA, you could remove the antenna from the receive port and start getting it closer to spots around/on the head unit to see where the signal is radiating from.

[SkylinesSuck]

Got a link to the tinySA? It just occurred to me I have the little baby mag antenna that came with my mxt275. Might that be helpful in sniffing it out?