USB Charger makes static in Com Radio.

T

Tim Hickey

Filing Flight Plan
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Aug 24, 2021
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Tim Hickey
In my build of a Murphy Rebel I installed two power ports, one having two USB sockets, and one standard cigarette lighter type. All hooked to 12 volt power. When I plug in the mini iPad I get enough static to break the squelch on my Garmin GTR 200. There is no adjustment of squelch on this radio. I have tried installing ferrite beads on the external cable, and on the hot line to the power port, but no improvement. I also tried wrapping the body of the USB power port with aluminum foil to block any stray signals, but, no improvement. Truthfully, I have not tried all three at once. Maybe I should try that next.
I know that some people make these ports and claim no interference, but they cost north of $200.
I'm hoping someone has a "fix" for this that I can afford.
Thank You
Tim Hickey.
 
Welcome to PoA!

IIRC the GTR 200 has a squelch adjustment. I have a $10 Anker USB adapter plugged into my 12V outlet, no RF interference on my GTR 225, or in any other plane I've plugged it into.

edit: also, pics of the Rebel are required.
 
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Yes! I had the same issue with my GTR 225 in a Husky with a factory installed 12V outlet. I ended up installing an aviation specific USB-C outlet.
 
When I installed a dual USB set up my experimental I placed it behind the seat away from the panel. I bought a fairly good one but I had heard this was a concern so I decided to separate it as far as reasonably possible from the radio & intercom.
 
GeorgeC said:
Welcome to PoA!

IIRC the GTR 200 has a squelch adjustment. I have a $10 Anker USB adapter plugged into my 12V outlet, no RF interference on my GTR 225, or in any other plane I've plugged it into.

edit: also, pics of the Rebel are required.
Click to expand...
The GTR 200 has automatic squelch. On or off, no adjustment. Rebel picture attachedIMG_1049 1.jpg
 
There is a squelch adjustment...see attached.
Note: some cigar lighter usb adapters are good, but not all. Anker is usually a reputable brand, but I have never tried their usb adapters.

8B27696F-EF15-41D9-A63D-ADB10AB2DB04.png
 
There are two likely sources of RFI from the usb power device. The device itself could just be spewing RF and the radio is picking it up over the coax. Or, the usb device is putting noise on the DC circuit.

the easy solution is find another usb power source. Anker gets good recommendations from others including myself for the plane. They are under 20 dollars

the harder solution is to get some clip on RFI chokes and put them on the coax by the radio and the power line. I’m into ham radio and deal with this all the time. https://palomar-engineers.com/ is a good source. Chokes run a few dollars each.
 
What about a dedicated power and ground that are both wired directly to the battery?
 
Some USB power adapters are noisy and some aren't. It seems to be hit or miss.

Like you, I have a cheap dual USB power & voltmeter in my Hatz, it has one standard USB 2.0 and one QC 3.0 (quick charge) port. The standard port is fine, but QC port causes my radio (Becker 2301) to break squelch. But I generally only need one port, and I don't have any QC compatible devices any more, anyway. If I really need to power two devices at once I'll just do it enroute when I'm not talking to anybody anyway.
 
What Dana said. Try a different usb power device and see if that fixes it. Some cause noise and some don’t.
 
Thanks, guys for the input. That Palomar web page has a “tips” section about getting rid of EMI. Worth reading. I will try more ferrite beads (chokes) to see if I can suppress the static.
Also, the GTR 200 has a squelch adjustment for the intercom system, but not for the receiver squelch.
If I am successful I will post here.
 
Check out table 3-4 of the GTR 200 install manual. There is a RF squelch. It is on the Com Setup page.
 
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