Connecting radio to Aux Port

Discussion in 'Mobile Radio' started by K9EJS, Jun 25, 2019.

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  1. K9EJS

    K9EJS Ham Member QRZ Page

    So I've used a seperation kit for the Yaesu 7900r, putting the radio under the passenger seat, and thought of instead of mounting an external speaker, I'd just connect it into the Auxillary Port on my car radio.

    Well I've ran into two issues. The first is if I turn up the radio any, I get the engine hum, so where would I place a ferrite? On the speaker cord, power cord, somewhere under the engine???

    The second issue is if I key up the microphone to talk, while talking, the radio switches over to FM/XM Radio and when I'm done switches back to Aux. Any thoughts, suggestions, tips?

    de K9EJS
  2. W5LZ

    W5LZ Ham Member QRZ Page

    Don't hook the thing up like that?
  3. K8ERV

    K8ERV QRZ Member QRZ Page

    Party Pooper!

    TOM K8ERV Montrose Colo
  4. W5LZ

    W5LZ Ham Member QRZ Page

    Am I also pooping on the party if I say don't touch a plate cap with your tongue? Or stick your fingers in a wall socket?
  5. K8ERV

    K8ERV QRZ Member QRZ Page

    Much better to show someone else how to do it.

    TOM K8ERV Montrose Colo
  6. AJ1G

    AJ1G Ham Member QRZ Page

    When you say AUX Port, do you mean the analog 3.5 mm stereo jack to input things like CD players, etc, or the USB AUX port? I have used the analog stereo aux input jack with my IC-7100 in both our 2012 Tacoome 4X4 and our 2017 Volvo XC60 SUV with no problems a all, in fact no RFI or EMI to the vehicles' audio or any other systems from the radio, even while transmitting.

    If you are indeed using the analog audio jack I would suspect that you may not have the chassis of your radio properly grounded to the frame of your vehicle. This ground is NOT the negative lead of your radio's 12V power cable. It should be a lead from the frame of the radio to something like one of the bolts that hold a seat frame to the the floor pan. But don't assume that any old bolt like that does in fact connect to the frame, I had a likely seat rail anchor bolt on the Volvo that did not have any continuity to the frame. Always check your intended location for your grounding wire for continuity back to where the vehicle's negative battery lead connects to the vehicle body/frame. Sometimes a bolt that looks like it is engaging with the frame doesn't due to paint acting as insulation, you might have to grind away the paint a bit with a Dremel tool to ensure good frame contact for your ground lead terminal lug.

    Another thing you could try AFTER you make sure your rig chassis is properly grounded as described above is to use an audio ground loop isolation transformer in the audio line from the radio headphone jack to the vehicle analog AUX input. jack Radio Shack used to sell these as "ground loop isolators. They should be available from other sources.

    Another problem might be if you are plugging a 3.5 MM STEREO tip ring shield connector cable into a 3,5 mm MONO tip/shield jack on your radio, that might short out one of the car stereo input channels. However, AFAIK, mot modern ham radios use 3.5 mm stereo output jacks to permit using any commonly available corded stereo headphones, with the mono radio output being sent to both the left and right channels of any headphone or external audio amplifier plugged into it.

    RTFM for the radio, it likely will instruct you re the need to ground the radio chassis to the frame and how to connect it to external audio devices.

    I don't have any idea on what would happen of you tried to interface to the car's USB AUX port, I would avoid doing that.

    Chris AJ1G Stonington, CT
    Last edited: Feb 6, 2020
    WA8FOZ likes this.
  7. W4EAE

    W4EAE XML Subscriber QRZ Page

    Ding ding ding...that is your answer!

    With this particular radio, even if you fix any possible grounding issues you will still have this problem. If you are using a TRS 3.5mm plug, your car's stereo has its left - to its right +. If you are using a TS 3.5mm plug, your the stereo's right + is short circuited to common -.

    Your key-up issue is probably how the stereo is designed. If it is not getting signal from the audio port, it switches back to FM. My car doesn't do this with the audio port, but it does with Bluetooth--making it completely unusable for amateur radio.
  8. KA9JLM

    KA9JLM Ham Member QRZ Page

    Use a terminating resistor in parallel with the AUX input.
  9. W5UAA

    W5UAA Ham Member QRZ Page

  10. K9PHT

    K9PHT Ham Member QRZ Page

    I mounted my Ham radio and monitor radio into two nice KENWOOD KES-5 External mobile speakers that I mounted on top of a piece of wood and slipped down into the truck drivers side door storage area...

    Gives me 'GREAT RADIO SOUNDS' and is on my side of the truck so I can turn it down somewhat and not blare out to disturb the wife...

    Roy's image

    These are available from AMAZON and most Ham radio stores...
    Roy Ken K9PHT
    Last edited: Feb 7, 2020

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