Lousy FM reception aftermarket radio. Antenna powered?

Discussion in 'Gen 2 Prius Audio and Electronics' started by R-P, Apr 2, 2019.

  1. R-P

    R-P Active Member

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    I've had an aftermarket radio for years and the reception is OK in my area, but seriously lacking in some others.

    I recently did a few runs with both my cars and was triggered by the immens difference between the JVC with Volvo V70 stock windiow antenna vs. JVC with Prius Gen2 stock antenna.

    So I googled a lot, many of the found links ending here on Priuschat but not getting (or finding) a definitive answer.

    Then I found this post, explaining that the power to the antenna amplifier in the Gen3 has to be manually added when using an aftermarket radio. Possibly this is automatically fixed by certain wiring harnasses (Metra) but I would like to check
    (1) is this is needed for the Gen 2?
    (2) if so, if my wiring harnass (probably Parrot, or at least added when my (now disabled) Parrot carkit was added by the previous owner) does indeed do this?
    (3) to check (2), know what wires need to have a 12V feed.

    If no one knows the answer, I may simply check this video again (@ 1:13 and 1:17) and unplug the 12V feed to the antenna and see if it is powered,
     
  2. R-P

    R-P Active Member

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    And the plot thickens...

    I used the above vid to get access to the antenna, I measured the voltage on the antenna power lead and there was none present.

    So I found my issue!!!

    Or so I thought... So I found a lousy radio station and applied 12V to the amplifier-power-lead. Reception no better.

    So I found the next culprit: broken amplifier.

    So I wanted to unscrew the base and see what I could see or measure there and I unscrewed the antenna and the reception stayed the same. So I figured more testing instead of unscrewing was needed, so I measured the powerdraw of the amplifier: 33mA, seems like a normal currentdraw (300mW of consumed power). And I unplugged the antenna under the headliner and the reception still stayed the same. The pin used for that is different from a standard antenna plug (why, WHY would they do this?????). The grounding is similar, but the "plus" pin looks very much like a 3.5mm headphone jack, but with a single contact instead of three (stereo) or four (stereo + microphone or stereo + video).


    So conclusions/issues:
    (1) the antenna amplifier gets no power, so probably wiring issue
    (2) the antenna does nothing for the radio reception so there's probably a wiring issue there too
    . Taking into account that my antenna does not contribute to the quality of my radiosignal*, my radio reception is actually quite good!!!

    Both issues could originate from behind the dash, so I guess it's back to disassembling that.

    Still need the wiring pinout to see what wire feeds the antenna amplifier in the OEM radio-plugs.

    I am dreading the step of needing to remove the whole headliner and all dashpanels to trace all wiring...




    (*) Obviously I did not drive around, so all this testing was done with the car stationary, but I am still confident that I can say that my antenna does little to nothing for my reception.
     
  3. douglasjre

    douglasjre Active Member

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    What was the cause
     
  4. audiodave

    audiodave Active Member

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    I bought a used one to replace my physically broken mount and tested it directly on my bench. Amplifier did nothing when I gave it 12 volts, neither did the other 04 used one I bought. So I figure it the amplifier itself. You can replace the whole mount with a new one for about $100. Or just add a aftermarket fm amplifier up buy the deck which is what I did.
    Posted via the PriusChat mobile app.
     
  5. R-P

    R-P Active Member

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    Still drive the car every day but haven't investigated further.
     
  6. douglasjre

    douglasjre Active Member

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    A resistor should have 4 bands. What's wrong w this picture
     

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  7. R-P

    R-P Active Member

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    It could also be a capacitor, which would only allow high frequencies to pass. I'll drop the enlarged pic in an electronics forum and see what the experts there have to say about it ;)

    Edit, as expected, they answered fast: it can be a lot of things. Many also suggested an inductance (coil).

    Advice to measure it: if you can measure resistance:
    coil: very low resistance
    resistor: specific resistance
    capacitor: (close to) infinite resistance

    Some suggested it might be a diode to e.g. quench static discharge. If this were the case, it should probably be between the center-pin and the ground. But by the looks of is, it sits in the signalpath from pin to wiring.
    A better close-up might help in determining this with certainty. Also for the colors. I see a green component with a separate blue ring, then some green of the green-component-color, then yellow, red, yellow and black. Do you see the same?
     
    #7 R-P, Sep 27, 2020
    Last edited: Sep 27, 2020
  8. douglasjre

    douglasjre Active Member

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    I measured no resistance
     

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