RF Interference and Hybrid Vehicles

techxpert211

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Nov 4, 2013
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Hey All, Ed (WRCQ448 on GMRS here)

I have a really dumb question. I have a close friend (ham op) who is having a big issue with his vehicle pretty much being a faraday cage. It’s a Subaru Crosstrek Hybrid. When it switches to hybrid mode pretty much any radio signal that’s not AM/FM/HD cuts out. It’s very annoying and rather than having to rip the car apart to try and fix this, where should we start? Just some information, the antenna sits on a diamond hood mount, wiring is run through either a grommet in the body or through the firewall, would have to verify. There’s almost no info that I could find that shows any sort of fix. Would ferrite be a good start? Do you need more info? Kind of lost here.

Thanks.
Ed
 

MTS2000des

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I would venture to say that in a hybrid or full electric there are a ton of RFI generating circuitry such as buck converters, switching power supplies, charging circuits, a ton of CAN buses, and CPU clocks galore from all the OBE that trying to fight it is the equivalent action of pissing into a fan. Ferrite would do little as the RFI is near field to the antenna, I'll bet if you sniffed around with a spec-an within a few feet of the car while the hybrid circuitry is actively operating/charging/discharging, you'll see blades of grass from DC to daylight.
 

mmckenna

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My wife is driving the same 2009 Ford Escape Hybrid that she's had for 11 years (145,000 miles now). Within a few days of it coming home from the dealer, I had a permanent mount NMO antenna on the roof and a radio installed. Been like that ever since.
No issues with RFI, no issues with switching back and forth between gas engine or hybrid or combination.

I don't know if the Ford is just quieter or what.

But I do have a permanent mount NMO dead center on the roof of the SUV. Coax is carefully routed away from all other vehicle wiring.
Power is pulled directly off the 12 volt batter in the engine compartment.

What would concern me about the Subaru install:
1. Using antenna mounts that may not make a good ground connection and/or provide a good ground plane for the antenna might be an issue.
2. Having the antenna in close proximity to the engine bay may not be helping.
3. You didn't mention anything about where power is sourced from.
4. You didn't mention anything about how/where the radio is mounted.

There's a good reason why we preach doing permanent mount NMO's in the center of the ground plane, and why we also encourage pulling the power feed directly off the battery. Often what we see is people taking shortcuts on the install.
 

techman210

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May 28, 2011
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If you determine that the noise is only getting into the radio from the power source, the Motorola TLN 5277 series filters are a good choice.

Newmar makes some nice filters, but they only filter high-frequency noises. The Moto works on high and low frequency noise. You can o-scope the power and see what you're dealing with and perhaps you can construct a LC filter network out of available parts.
 

jaspence

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I have a Ford C-Max, and it does not cause any problems with my scanners or ham radios. This is my 3rd C-Max, and none of them have given any trouble.
 
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