Yaesu VX-5R Interfaced to Computer

Discussion in 'Radio Circuits, Repair & Performance' started by kb1kyh, Apr 27, 2008.

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  1. kb1kyh

    kb1kyh Ham Member

    I had an idea for a few small projects, and they involved interfacing my VX-5R to a computer. With the CT-44 adapter, it appears as if I'll be able to use a 2.5->3.5mm adapter from the microphone jack to the line out jack on my computer. I would like to point out before anyone makes any comments that I'm not planning on doing anything illegal such as playing music or sound effects. Will the output on the computer key the HT, or does something need to be done to over ride the PTT?
     
  2. K5SYN

    K5SYN Ham Member

    I have a VX-5R also and at one time I wanted to do what you are suggesting here. The CT-44 doesn't provide any isolation, it's just a breakout for the odd 4 ring Yaesu connector, so be mindful of that. If your soundcard voltage is high it can damage the 5R.

    The CT-44 doesn't enable any sort of vox capability, so just having audio running through it won't cause the HT to key up. Check page 11 of the manual for the required resistance to open the PTT circuit.

    Best bet, make or buy an interface which will have all the necessary bits (isolation, PTT activation, cables). There are several places to buy them online. Just be careful when asking questions of the sellers, some don't even like to bother if they know it's for an HT "because of the duty cycles involved." Personally, I believe if I fry my gear, it's nobody's fault but my own!

    Hope this helps some :)
     
  3. kb1kyh

    kb1kyh Ham Member

    Yup, I accounted for all that. I figured I'd turn the volume all the way down on my sound card, then slowly turn it up while monitoring the transmission out of the 5R on another radio until its suitable. I suppose I could also get a microphone for the 5R and expose the wire and measure the voltage from there, then adjust the sound card's volume accordingly.

    I saw that manual page, but for some reason only thought it applied to a data modem interface. What exactly does the PTT portion of the circuit go to? Does it need an applied voltage, does it go to ground, or does it connect back to the MIC portion to create a parallel circuit? And do you or anyone else know what purpose the 10 microfarad capacitor serves?

    I can't find any interface cables that might be of use since a lot of radios use 5 pin or 8 pin DINs, and that's what all of the cables seem to be made for. I agree with you on the last part. It really wouldn't be fair to blame my own mistakes on someone else :p
     
  4. K5SYN

    K5SYN Ham Member

    I don't know enough about electronic circuits to be able to answer about the capacitor, or how to setup the PTT. I'd have made my own interface if I could have figured it out! The ones I see for sale seem to use a serial port, or usb for newer models to let the packet software handle the PTT.

    I lucked out and found a TNC at a hamfest, made a cable to go into the CT-44 and worked from there. I ended up moving to a rural area and had to put packet on the back burner until I can get an antenna higher up.

    Edit: There are a few places to buy the 4 ring connector Yaesu uses, if you want to skip the CT-44 entirely. I forgot until just now that the previous owner gave me one as a spare, since he made his own programming cable.

    Tower Electronics has them.
     
    Last edited: Apr 30, 2008
  5. N5RFX

    N5RFX Ham Member

    Page 11 says it all. The cap keeps dc from going back to your sound card and keeps any soundcard dc from going into the radio. The PTT will originate from your interface. Here are some examples. You will use an NPN transistor whose base is connected to the DTR or RTS (more common) pin on your serial port. When the transisor conducts it will put a ground on the right side of the 2K resistor on page 11 of your radio manual. That causes the radio to key. This is pretty common in most handhelds.

    73,
    Mark N5RFX
     
  6. kb1kyh

    kb1kyh Ham Member

    I have an older manual, and it doesn't have any of that in it which is why I asked. Thanks for explaining that.

    I'm not using my radio for any data modes, so I planned on writing my own program really quickly. As a result, I just planned on using the output from my sound card to drive the input on the HT. I'm going to try to make something that'll detect when there's output from the soundcard and mimic what you just described. This is for the sake of not having to run extra wires from the serial port and to account for the fact that most newer computers don't have a serial port.

    Just to be clear, the right side of the transistor is going to ground and the left side is connected to the PTT portion of the circuit on page 11, correct? If that is right, then thank you for your response, you helped tremendously.
     
    Last edited: Apr 30, 2008
  7. N5RFX

    N5RFX Ham Member

    Picture worth a thousand words

    Since a picture is worth a thousand words, take a look at this and see if it helps.

    73,
    Mark N5RFX
     
  8. K5SYN

    K5SYN Ham Member

    Awesome! Leave it to the experienced guys to make it easy for us mere mortals to understand :)

    Thanks!
     
  9. kb1kyh

    kb1kyh Ham Member

    Awesome, that does help. Thanks very much :)
     
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