Yaesu VX-3R Interferes with Itself

Discussion in 'Radio Circuits, Repair & Performance' started by KE8BDQ, Dec 16, 2017.

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  1. KE8BDQ

    KE8BDQ Ham Member QRZ Page

    Hey guys. I'm trying to get the audio on 2m out of this HT and to a PC but whenever I plug anything into EAR the signal just dies and there is only static. The longer the cable, the worse it gets. It doesn't matter what cable and weather or not it's plugged into the PC. It even does it with headphones. Moving the HT doesn't change anything either.
     
  2. W2WDX

    W2WDX Subscriber QRZ Page

    A few questions. What input type on the PC? Is it the line input (light blue) or a mic input (pink)? Also you are aware that the TRS connection is stereo on the computer. You need to wire the connector going into the computer properly. I suspect this is where you may be having trouble.
     
  3. K7JEM

    K7JEM Ham Member QRZ Page

    I think the ear jack is dedicated to FM receiver use. The speaker mic jack would work, but it is 4 conductor, not 3.
     
  4. KE8BDQ

    KE8BDQ Ham Member QRZ Page

    I was trying it on mic input. There doesn't seem to be much difference between mic and line on this PC for some reason. I also tried a C-Media USB sound card with the same result. It isn't the PC though since I'm getting the same result with headphones that aren't even attached to the PC.

    Unfortunately I don't have the 4 pin plug. I should probably get one though. There is some reception and output on the EAR jack, it's just greatly reduced.
     
  5. KA9JLM

    KA9JLM Ham Member QRZ Page

    If the connector is 4 pins, You need a matting 4 pin connector.

    Or a CT-44.

    Also the mic in on most computers is mono, Not stereo.
     
  6. W2WDX

    W2WDX Subscriber QRZ Page

    Actually the standard established (PC2001) for mic inputs on computers is as follows:

    AUD–0331. If implemented, analog microphone input meets PC 2001 jack and circuit requirements

    This requirement enables users with electret or dynamic microphones to connect the device to their PC and achieve consistent results. This requirement also maintains compatibility with the installed base of microphones. For information about headset microphones, see AUD–0332, “If implemented, close-speaking headset microphone meets PC 2001 performance requirements.” If the PC has an analog microphone input, it must meet the following specifications:

    • Three-conductor 1/8-inch (3.5 millimeters) tip/ring/sleeve microphone jack where the microphone signal is on the tip, bias is on the ring, and the sleeve is grounded. This design is optimized for electret microphones with three-conductor plugs, but will also support dynamic microphones with two-conductor plugs, where the ring and sleeve are shorted together.

    • Minimum AC input impedance between tip and ground: minimum, 4 kilohms.

    • Input voltages of 10–100 millivolts (mV) must deliver full-scale digital input, using software-programmable gain.

    • Maximum 5.5 V with no load, minimum 2.0 V with 0.8 milliampere (mA) load, direct current bias for electret microphones.​

    • Minimum bias impedance between bias voltage source and ring: 2 kilohms.

    • AC coupled tip
    However, using the microphone input is the wrong choice in this case. Using the line input would be better. The microphone input may be overloaded by the "ear" output of the radio, which is essentially a speaker output signal wise.

    The best choice for this is to use the ear jack on the radio into the line input on the computer, and use a TS mini jack or a TRS jack, but connectors should both be the same on each end of the cable. The VX-3R ear jack is stereo also. However, the way you are doing it now you have the bias voltage on the computer mic input connected to one of the output channels on the radio. Using the line input should do the trick, since both use the same wiring convention. That being stereo, or stereo shorted to mono.
     
    Last edited: Dec 17, 2017
  7. KE8BDQ

    KE8BDQ Ham Member QRZ Page

    Okay that is all great info and good to know, but it still does it weather it's plugged into a computer or not. Plugging headphones into the EAR jack still affects the reception as described above.
     
  8. KA9JLM

    KA9JLM Ham Member QRZ Page

    "There is a special function that allows you to listen to either the AM or FM bands, and have it interrupted if you receive amateur comms."

    I wonder if a menu setting needs to be tweaked ?
     
  9. G3YRO

    G3YRO Ham Member QRZ Page

    SO frustrating when people don't read what you post properly !

    As you say, this problem is nothing to do with plugging it into a PC . . . so all the above info, although useful, is nothing to do with this issue.

    From what you're describing, as soon as you plug a headphone lead into the rig, you lose the received signal, and just hear noise. So is that as if you have simply unplugged the antenna, and have the Squelch turned off (so a lack of signal produces noise, not silence) ?

    Second question - what antenna are you using on the rig?

    Can you connect a proper antenna to it, via coax - and if so, does this fault still occur?

    Roger G3YRO
     
  10. K8MHZ

    K8MHZ Ham Member QRZ Page

    Yaesu uses a proprietary plug pin combo for their HT's. You either have to buy the plug from Yaesu, or modify one, otherwise you will have problems like you say. I went through this with my FT50RD.
     

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