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Old 12-02-2019, 04:02 AM
Piper J3's Avatar
Piper J3 Piper J3 is offline
Join Date: Nov 2014
Location: Hinckley, Ohio
Posts: 1,898
Default USB Power Receptacle Comm Interference

I installed a USB power receptacle for my iPad. I'm beginning to wonder if it is causing comm radio interference. My question is... what are symptoms of USB power plug as related to comm? What type of interface would be noticeable?
Jim Stricker
EAA #499867
PPL/ASEL 1970 - Sport Pilot since 2007
80 hrs Flying Aeronca Chief 11AC N86203
1130 hrs Flying 46 Piper J-3 Cub N6841H
Bought Flying RV-12 #120058 Oct 2015 with 48TT - Hobbs now 564

LSRM-A Certificate 2016 for RV-12 N633CM
Special Thanks... EJ Trucks - USN Crew Chief A-4 Skyhawk
MJ Stricker (Father & CFI) - USAAF 1st Lt. Captain B-17H
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Old 12-02-2019, 07:12 AM
John-G John-G is offline
Join Date: Jan 2012
Location: Northeast Ohio
Posts: 643


As you have apparently discovered ... not all USB charging ports are created equally. Some units generate way more electrical noise than others. I think the root of the problem is if a switching regulator is utilized in the design, it also needs to be accompanied with some filtering within the unit to reduce the electrical noise created by the switching regulator.

I too plan on adding a notepad and have purchased a USB power port at the phone store .... but have not tried it out in the airplane yet. Perhaps you could try asking some friends that have various USB power units in their cars to let you try them in your airplane.

Below is a VAF link talking about the noise issue along with links to units that work well. I know Stein Air has a unit that they say has reduced noise.
RV-12 Wings, Empennage, Fuselage, Finishing, Avionics and Powerplant kits all completed
Now Flying!!

Dues paid until September 2020
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Old 12-02-2019, 07:24 AM
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MWH265 MWH265 is offline
Join Date: Feb 2016
Location: Virginia
Posts: 82
Default USB

I was talking with my avionics guy about this a few weeks ago. He said that usually the cheap ones are just that, cheap. That also goes for the plugs you can plug into a power outlet (cigarette lighter for those of us old enough to know what that is) that will accept a USB cord. He said most of the "quality" plugs that are not FAA/PMA are fine.
RV6A Owner/Operator
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Old 12-02-2019, 07:55 AM
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N941WR N941WR is offline
Join Date: Jan 2005
Location: SC
Posts: 12,887

Disconnect it and see if the noise goes away, that will answer your question.

I have a cheap USB port in my plane and it didn't add any noise to the system.
Bill R.
RV-9 (Yes, it's a dragon tail)
O-360 w/ dual P-mags
Build the plane you want, not the plane others want you to build!
SC86 - Easley, SC
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Old 12-02-2019, 08:12 AM
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airguy airguy is offline
Join Date: Oct 2006
Location: Garden City, Tx
Posts: 4,985

Get a toroid and wrap the power/ground wires a few times through that, as close to the device as you can get them, and wire-tie it in place. That will knock down a lot of the noise, likely down to the acceptable level.
Greg Niehues - SEL, IFR, Repairman Cert.
Garden City, TX VAF 2020 dues paid
N16GN flying 650 hrs and counting! IO360, SDS, WWRV200, Dynon HDX, 430W
Built an off-plan RV9A with too much fuel and too much HP. Should drop dead any minute now.
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Old 12-02-2019, 08:43 AM
j-red j-red is offline
Join Date: Dec 2015
Location: Lewes, DE
Posts: 363

Been right here recently. The first usb charger was from west marine. Didn't make any noise unless it was actually charging but when a device was plugged into it, it was "broadcasting." Tried ferrite clamps several different places but no effect. Finally spent $20 and bought this unit from Spruce. It must be internally suppressed whereas the original wasn't because it's totally silent now and I've ditched the ferrites.
Rebuilt RV-6A N94CR
RV-8 N803DR completed, flying.
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Old 12-02-2019, 05:00 PM
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plehrke plehrke is offline
Join Date: Sep 2006
Location: Defiance, MO
Posts: 1,621

I got a cheapy from Amazon wired to main bus and works great. Mounted right by the radio stack and no issues. Also have a cheapy cigarette lighter plug only a foot away with a twin USB adapter plugged in. Power a iPad, Dual XGPS170 ADSB In, and a Hudly HUD. Never have had radio interference.
Just lucky, I guess.
RV-6A - 13 years over 900 hours
Based at 1H0 (Creve Coeur)
Paid dues yearly since 2007

Last edited by plehrke : 12-03-2019 at 03:46 AM.
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Old 12-03-2019, 05:42 AM
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pjc pjc is offline
Join Date: Apr 2012
Location: Tampa, FL
Posts: 129

I have had good (noise free) service from this cheapy one in my RV6 with both a Valcom and Icom radios. Just dumb luck though, I didnít do any research before trying it. YMMV.

Vans RV6 flying
SZD 48-2 flying
2018, 19, 20 Dues paid
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Old 12-03-2019, 08:10 AM
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rv8ch rv8ch is offline
Join Date: Feb 2005
Location: LSGY
Posts: 2,953
Default Blue Sea

I've heard these have no noise, but I have not tested them yet while flying. I pulled it apart if you want to see the guts.

Mickey Coggins
"Hello, world!"
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