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).

[tweiss3]

https://www.tinysa.org/wiki/

 

Its like the NanoVNA, but its a spectrum analyzer. I have one, and its a pretty neat tool.

 

You can buy it from R&L: http://www.randl.com/shop/catalog/product_info.php?products_id=75243&osCsid=ds1r4m541l1jqb3o0g37bvcoi7

[SkylinesSuck]

So I got the ferrite beads and snapped a few on every single wire coming out of the back of that stereo. I even disconnected various different wires and bundles of wires to troubleshoot including the antenna and speaker wires. The only thing that has any effect is turning the unit off. I can turn the wifi and bluetooth off, but that has no effect. I don't think there is a way to turn anything else off.

 

So it looks at this point like maybe shielding the unit is the only possible option other than getting a new unit which isn't outside the realm of possibility, but not something I'm gonna do next week. Any thoughts on trying to shield it somehow? Considering it's a wireless Android auto unit (which is a feature I plan to keep) I'm thinking anything that would be effective would also probably kill my wifi connection for Android auto, but I'm willing to tinker.

[SkylinesSuck]

Just ordered this:

 

https://www.amazon.com/dp/B085QDDJLS/ref=cm_sw_r_cp_apa_glt_fabc_Q3JCYM5721VRD36E5ZRP?_encoding=UTF8&psc=1

 

I'll mess around with it and see if it helps. I'm guessing since one end (the screen) will always be exposed though there is probably nothing that can be done. For less than $20 though, I'll try. Some of the reviews by people looking to make hats to block Bill Gates from controlling their minds were worth the price anyways!!

[serrasalmus]

my only concern with that is it might block your wifi and bluetooth also

[SkylinesSuck]

Yup, but for <$20, I'll experiment a little.

 

Also one thing I did this morning was hook up the little 5" mag antenna that came with my midland mxt275 and moved it around. When I located it on the front driver's side front fender as well as the mount for the CB antenna above the opposite corner tail light, no interference. So maybe I'll try moving the GMRS antenna as well.

[SkylinesSuck]

I swapped sides on the CB and GMRS antennas today. Boom, no interference. I did notice though as soon as I provided power to the rear camera (which I had to disconnect during my rewiring) I got interference again even with the antenna on the other side, even when the backup camera wasn't "on." It has 2 12v inputs. One is the 12v trigger on the reverse wire, the other is switched 12v power to power it and so I can select the input and check on a trailer or whatever.

 

So for now, I put both power wires on the reverse switch so I only have to worry about interference in reverse which is a non-issue. I might try a different camera later to see if that makes a difference and then I can wire it up like before so I can check a trailer if needed. Not crucial though.

[serrasalmus]

good job tracking it down. im working on alternator noise only on 1 channel, and its just a listen as its the fd dispatch. sometimes its there and sometimes its not.....

[tweiss3]

Very interesting. I wonder if your shielding fabric on the cable will help.

[mbrun]

I swapped sides on the CB and GMRS antennas today. Boom, no interference. I did notice though as soon as I provided power to the rear camera (which I had to disconnect during my rewiring) I got interference again even with the antenna on the other side, even when the backup camera wasn't "on." It has 2 12v inputs. One is the 12v trigger on the reverse wire, the other is switched 12v power to power it and so I can select the input and check on a trailer or whatever.

 

So for now, I put both power wires on the reverse switch so I only have to worry about interference in reverse which is a non-issue. I might try a different camera later to see if that makes a difference and then I can wire it up like before so I can check a trailer if needed. Not crucial though.

Nice job tracking it down.

 

 

Michael

WRHS965

KE8PLM

[OldRadioGuy]

I totally missed that the "remote head" causing interference is completely wireless. 

If the wireless unit is entirely causing the interference you're probably stuck with it. 

The guilty unit is transmitting GMRS noise and I can't think of any way to change that without going inside. 

Obviously that's not an option. 

 

If there are no wires connected to the remote head I don't see any way to mitigate the radiation while allowing it to still work wirelessly. 

You could try locating it in a nook where it's partly shielded from your GMRS antenna but that's pretty tricky.  

I guess maybe you could put the head unit in a metal box when not actively using it. 

 

I wouldn't assume that the "head unit" is out of spec because it's very close to a very sensitive receiver. 

 

I used to do EMI compliance testing and all digital devices make tons of RF noise. 

Sporadic noise gets much more lenient treatment than steady signals. 

So these can exceed the limit for steady signals (it's called quasi-peaking) 

This sporadic noise does bother our radios so not a good deal for us. 

 

It's a very noisy RF world we live in today.  It's amazing the the problem is not even worse. 

 

Vince

[bhawkins4194]

Sorry for bringing up an older post, but wow you just saved me a ton of headaches. I was having the same issue and sure enough it was my aftermarket hard wired backup camera. I unplugged the power and the bars dropped off the screen and the static stopped. What did you end up doing to fix it? I mean I guess I can remember to unplug the power to the backup cam when I go off-road but just seem strange why the camera is causing the interference.