RF Issues In Late Model Mobiles?

Discussion in 'On the Road' started by N1SP, May 8, 2019.

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  1. N1SP

    N1SP Premium Subscriber QRZ Page

    Been many years since I have had a vhf/uhf mobile in my vehicle. Always wired power directly to the battery and never had any issues.

    Today's vehicles now have much more complex electronics than just a few years ago- not only an ECM, sometimes rf relayed TPMS, SRS, "wireless throttle" and a PCM as well. I work in auto parts and diagnostic tools and see a lot of crazy, expensive stuff happen. Because of this most any dealership's service manager (who does not understand what you are talking about) will quickly tell you radio installation will void your warranty.

    Question is... anyone ever have problems with their on board computers caused by their radio installation? Or know any extra precautions that should be taken in today's vehicles?

    In my case looking to install a vhf/uhf mobile into a 2016 Honda CRV- clean wiring to the battery, clean coax and antenna installation. Figure if some of the HF mobile guys can run an amp and a physically short antenna, I should get by without a hitch.

    Appreciate your input
  2. K4KWH

    K4KWH Ham Member QRZ Page

    While one cannot offer guarantees, It should be quite do-able. What I would do is, first, consult the manual to see if Honda speaks of radio installations. Next I would route the power and coax cables away from the ECM. Another way is to snake the cables thru a "grounded" tunnel. I took several lengths of braid strap and wrapped it around the cables themselves, grounding the ends of the braid at various points along the route. It might be overkill, but during this process when I installed my radio (IC 706 MKIIG) and fired it up on HF, something was wrong. Instantly I knew I was getting RF into the ECM because the engine would almost die when I transmitted. I went back and discovered that one of the grounding bolts had worked loose and the ends of the braid were flopping unhindered. I tightened up the grounds, checking ALL of then, not just the one that came loose. I tried it again. VIOLA! No engine stall, no weird sounds from the speaker, and all was well. So I think the key is ground, ground ground. If you think it needs it, do it!;) Keep grounds short as possible, try to stay away from the ECM by routing it to the other side. Unless you're running gawsh-awful power, you should be fine. Come to thing of it I saw a CRV at a recent hamfest with a VHF antenna on it!
  3. K0UO

    K0UO Platinum Subscriber Platinum Subscriber QRZ Page

    Not with VHF/UHF, but HF for sure. Even after spending days on grounding and adding ferrites. I have had the ABS lock up all the breaks at 70mph!! Service engine lights of all types, air bag warning.
    On my 2018 chevy duramax truck the main CPU box went out and had to be towed just after I keyed up, the truck had 6 miles on it!!! I'm not they only one that have had this and it gets worst every year.
    Just stay at it if you have issues, you can win!
  4. N1SP

    N1SP Premium Subscriber QRZ Page

    Yep, right along the lines I was thinking as far as grounding/ shielding. Going to start hunting for any TSBs from Honda. Not planning on over 50 watts but thought I'd throw it out there in case someone ever had an issue.

    Have a friend/ client at our local Ford dealership- there are some TSBs for Crown Vics and Explorers, as often have radio and computer gear installed for public safety.

  5. KB3WFV

    KB3WFV Premium Subscriber QRZ Page

    Hi Randal,

    Any two radio system installed correctly will work properly and not cause interference with the vehicle systems. The most Important things are the antenna and the proper mounting of the antenna. A resonant antenna at the desired frequency, correctly mounted and properly tuned, including using an inductive matching solution at the antenna feed point, will ensure that all of the RF goes out the antenna.

    The more metal under the antenna the better. Mount the antenna in the center of the roof. A through the roof NMO mount would be best. A quality magnet mount in the center of the roof would be the next best.

    For a LOT more information on mobile installations and operation see this web site.....




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