FM interference / signal degradation

Modified and aftermarket systems, lights, wiring, etc.

Moderator: F9K9

FM interference / signal degradation

Postby plantone » Mon Aug 07, 2017 10:52 am

i recently got a MIFI to use as a dedicated hotspot in my truck for my android indash for the navigation.

i mounted it up on the B pillar, above the seatbelt pivot, and snaked a USB cable behind the plastic for charging.


since i had both battery power and a turn on wire back behind the rear seat for the amp, i picked up a under dash USB power port ( http://a.co/1BBlzUK ) and wired it up on a relay i had ( http://a.co/2PH3uKM ) so that it would only charge when the vehicle was operating.


however - my FM signal is getting some bad interference when the MIFI jet-pack is plugged into the USB. As soon as i unplug it, goes away immediately.

i fused both the always on power and the turn on wire pre-relay with an inline mini fuse to protect everything in the event of any kind of a ssurge. i put a 5amp fuse on the turn on wire, and a 10 amp on the battery feed. everythings grounded through the ground block that feeds the amp (i had a pair of power distribution blocks installed back there when the amp/sub got put in)


so i'm wondering what my options are to correct this - short of plugging and unplugging the MIFI as needed.


do i switch the relay to the white wire (87a?) and have it charge when the vehicle/radio is off? (i'd rather not go there, but it would be a 2 minute fix)
will a ferite core noise suppressor fix it? ( http://a.co/dGmKu0q ) if so which wire does it go onto - i'm guessing the blue turn-on wire going to the radio?


#ihate12v :mrgreen:
"Politics: The art of appearing candid and completely open while concealing as much as possible." - Frank Herbert

"Your mother was a hamster, and your father smelt of elderberries" - The French Fellows
--------------------------------------------------------------------------------------------------

'03 LS Crew Cab
plantone
Enthusiast
Enthusiast
 
Posts: 36
Joined: Tue Jul 19, 2016 10:11 pm
Location: Oakland County, MI

Re: FM interference / signal degradation

Postby ApproachMedium » Sun Sep 17, 2017 8:10 am

Is it on the passenger side or driver side b pillar? It sounds like the MIFI box is interfereing with the ground plane of your vehicle when its ground plane is attached to your vehicle via the USB ports ground. You may need to try a different location, maybe in the center of the truck like the center console.
Knowledge has no value unless its shared with others.
Exploration Machine- 02' CC V8 swap. 300K+
Portable Roller Coaster- 07' MKV VW GTI
Its another Jeep- 98 TJ
ApproachMedium
Crew Elite
Crew Elite
 
Posts: 969
Joined: Tue Nov 17, 2009 1:20 am
Location: Jersey Shore

Re: FM interference / signal degradation

Postby plantone » Tue Sep 19, 2017 10:21 am

its on the passenger side b-pillar, right at the top of the plastic before you get to the headliner.

here's my ignorance showing itself - how would moving the hotspot to another location change whats happening if its a ground related issue? the power supply's ground point would not be changing. is it some kind of EM emission causing the problem you think based on the proximity to the metal directly under the b-pillar plastic? or is it a possible issue with shielding (or lack of) with the USB cable itself based on its proximity to the frame behing behind the plastic?

i'll try a different cable today and relocate the hotspot and see if it goes away.
"Politics: The art of appearing candid and completely open while concealing as much as possible." - Frank Herbert

"Your mother was a hamster, and your father smelt of elderberries" - The French Fellows
--------------------------------------------------------------------------------------------------

'03 LS Crew Cab
plantone
Enthusiast
Enthusiast
 
Posts: 36
Joined: Tue Jul 19, 2016 10:11 pm
Location: Oakland County, MI

Re: FM interference / signal degradation

Postby ApproachMedium » Thu Sep 21, 2017 8:26 pm

yea id try to go for a higher end usb cable with shielding. it may be the cable itself thats creating an "antenna" and inducing the noise into the FM antennas ground plane. Moving the box could help, i had an issue with my shallow sub for my volkswagen causing FM interference if my amp was on. the large diameter of the voice coil in the sub being too close to my rear window glass which had the Fm antenna in it was enough to screw it up. I tried putting a ground loop RCA isolator between the amp and the radio but that did not change anything. i had to change the position of the sub in my trunk to clear it up.
Knowledge has no value unless its shared with others.
Exploration Machine- 02' CC V8 swap. 300K+
Portable Roller Coaster- 07' MKV VW GTI
Its another Jeep- 98 TJ
ApproachMedium
Crew Elite
Crew Elite
 
Posts: 969
Joined: Tue Nov 17, 2009 1:20 am
Location: Jersey Shore


Return to Electrical Modifications / Audio / Video / Lighting



Who is online

Users browsing this forum: Google [Bot], Majestic-12 [Bot] and 1 guest