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MPET-Baofeng Speaker Mic connection guide

**** Due to changes in Baofeng manufacturing practices, please trace the internal wiring of your speaker/mic****

OK, now that the disclaimer is done, I have, with the help of CJ, been testing the internal wiring of the ubiquitous Baofeng Speaker/Mic. Many members are planning on using this speaker/mic for their MPET projects. I believe the accompanying wiring diagram can be used to successfully make the appropriate connections. As of this posting, this still needs to be tested, but the research looks sound. If someone is at the point of making these connections, and is willing to test them, please let me know.




  • I did trace the wiring on my Baofang and intended to hook it up just as you've shown. Here's the problem I'm having: without connecting pin 14 (ptt) to anything as soon as I connect pin4 to the mike (ring of 3.5 mm plug) the ritron begins transmitting (12 and 15 are connected to the tip and sleeve respectively of the 2.5mm plug) . the speaker works fine by itself with nothing connected to the mike jack. the ptt switch works when connected to the sleeve of the mike jack as long as nothing is connected to pin 4. I checked all wires back to the db 15 and there are no shorts or opens. I looked at the schematic and it appears pin 14 is connected to pin4 through resister 370 (upper right corner of sheet 2) I don't know if this is causing the problem or if we have to redo the connections inside the baofang, there are only 4 wires in the cord the tip of the mike plug and the ring of the speaker plug are not used. I've been messing around with this problem for about a week with no luck. Any suggestions?

  • Hello Charles, It looks like the manufacturers of the Baofeng mics are less than exact about how the wires are connected in the mic. Some mics appear to have the wiring reversed on the 2.5 mm jack. Therefore some have the ground on the tip, and some have the ground on the barrel. I "think" this is the problem. Let me do a little more research to be sure. You can test by unsoldering the wires in the mic, and testing where they connect on the jack. Unsolder and test one wire at a time as to not get them confused. If you choose to go this route, please post your findings to help me confirm my guesswork.

  • Thank you very much K2JLV, KD2BID and KC2NDA...for working through this issue.

    As a beginner, I'm listening and watching and learning. I find this trouble-shooting investigation quite instructive.

    I'm working on the carpentry part of my project this week and hope to get to the wiring next week.

    I'll report on the results of my experimentation.

    Aaron, happy to offer up my Baofeng speaker/mic for further testing...even if it blows up...a small price to pay for the continued pursuit of knowledge.

    Thanks again. Paul AC2UQ

  • Here are pictures of the Baofeng speaker mike board

    I connected pin 12 speaker out to the tip of the 2.5 jack and the sleeve to ground. pin 4 mike out to a momentary switch to the ring of the 3.5mm jack and that sleeve to ground. pin 14(ptt) is not connected to seems to work audio out of the speaker, transmits voice with the switch closed.

    the terminals on the board are labled from left to right m m- ptt sp- sp+

  • edited May 2017

    One thing to be noted here is that there needs to be a volume (10k) pot put inline with pin 12. Otherwise, its full volume all the time.

  • edited March 2017


    See schematic diagram in post above.. I had the same issue. I was hoping someone could test the Speaker with the above circuit. If the +Speaker is not hooked up at all, the PTT/MIC will work perfectly. As soon as you hook the +Speaker into the mix, the unit will start transmitting. I added a simple diode to fix this. My speaker is very low, so I am not actually sure if it is working or not. I was hoping you might be able to test the speaker and let me know what yours is doing.

    The diode here will most likely clip the audio causing distortion. I would like to try the circuit and see what might happen with a scope. Maybe a higher voltage Zener diode might work? I am leading more towards an audio optocoupler.


  • Aaron...thanks for going to the trouble to create the circuit diagram showing the addition of the 1N4148 makes sense to me why that may work and I will purchase the diode and try it out.

    By the way, how did you add that information to the circuit diagram...great editing...are you using a special 'photo-shop' type software or something.

    This MPET/Ritron project has helped me to hone my circuit diagram reading skills and that is a positive unexpected outcome for me. I hope to move on to an 'arduino expansion' once I complete this phase.

    As you can see from the attached pics, I'm rooting for a 'Bafeng solution' since I've already drilled the holes for the two prong speaker/mic connection and would like to avoid drilling more holes in the plexiglass. Also did not anticipate this project would give me a chance to practice my carpentry skills...all good. Thanks.

  • Looks great Paul!

  • wow... thats cool Paul!

  • I tracked down a sketch of a Ritron speaker mike. It looks like it would take a fair amount of work to get the baofeng to emulate it, though it is much simpler than the baofeng.You would probably have to cut the traces and run your own wires. Any other suggestions ?

  • Gorgeous work Paul!

  • edited April 2017

    That looks like a SWEET shop! =) I can't wait to come over and see it!

  • I am writing this post on Thursday evening, April 27, 2017.

    I have wired up most of my MPET/Ritron "Visible Radio" and excited about moving ahead.

    I'm happy to 'experiment' with my Baofeng speaker/microphone that was recommended to us at the beginning of the project.

    However, I am having trouble, as a beginner, understanding the exact 'experiment' that I can run.

    On March 1, K2JLV provided a very clear circuit drawing with the following connections recommended:

    A. Baofeng Microphone SLEEVE to Pin 14.
    B. Baofeng Microphone RING to Pin 4
    C. Baofeng Speaker TIP to Pin 12
    D. Baofeng Speaker SLEEVE to Ground

    JLV's post ends with the words: "If someone is at the point of making these connections, and is willing to test them, please let me know."

    So...this post is to let the MPET Team and K2JLV know that AC2UQ is indeed ' that point...'

    Please let me know the exact nature of the 'test' I should run. As a beginner, I do not want to blow up the Ritron and I need some help.

    Thanks so much.


  • On March 3, 2017 KC2NDA provided a very clear circuit drawing with the following connections recommended for the Baofeng speaker/microphone.

    A. Baofeng Microphone Sleeve to pin 15. [Note: KD2JLV showed the SLEEVE connected to PIN 14 on March 1]

    B. Baofeng Microphone RING to Pin 4. [Note: This agrees with the post by KD2JLV]

    C. Baofeng Speaker TIP to PIN 12 with a 1N4148 Diode? in series between the TIP and Pin 12. [Note: KD2JLV showed no device in the circuit]

    D. No other Speaker connections are shown. [Note: KD2JLV showed the Speaker SLEEVE connected to PIN 15 (GROUND)

    Aaron's post includes the words, "I did not test the speaker. If someone can please test the speaker to see if this circuit works."

    Well, here I am, ready to test. However, I also need help resolving the difference between the two circuits provided on this MPET/Ritron thread.

    AC2UQ standing by, hoping for help and instructions. Undaunted. Onward and Upward.

    P.S. As a beginner I have no idea what an 'optocoupler' is and I'm not sure a man my age should be using one...however, always willing to try something new.

    KC2NDA's March 3 post ends on a hopeful note:
    "Remove the diode and speaker connection and you should have a perfectly working Microphone for the Ritron."

    I don't understand the above sentence. Help requested.

    Onward and Upward.


  • I am not going to provide direction on hooking up a Baofeng mic, because I feel its an inferior product to be used with the MPET but it could be done. I rather not provide false information which may frustrate people.

    My direction took me to use the Yaesu style connection as noted here "Yaesu & MPET". I primarily wanted this for "data" use but also works for voice applications.

    Others who went the Baofeng mic direction seem to have given up and bought a Ritron mic.

    If you really, really want to pull my arm HARD, I will help get it figured out, Paul and then you get all the credit.


    Optocoupler: 4N25 is a part number I have a TON of. Very handy items. If I see you at the OCARC hamfest, will give you a few to experiment with.

    Think like this:

    One side has a LED (like your TV remote control) and the other end is the receiver end (like on your TV). They seal up both components in a blob of plastic so no annoying person walks in front of you holding the remote, preventing you from changing the channel. Then you have two leads for each side.

    There opto couplers (or opto isolators) prevent a ground loop and some fantastic "isolation" to protect a circuit. Many, many use cases for it. Wikipedia has a good article

    For the MPET, I would not use an optocoupler for anything to do with an audio path for jsut a simple microphone, but did use one in my circuit for keying the PTT on the Echolink node (NOTE: If I chose to use it for transmit). Optocouplers do work great for audio applications though and are much smaller than an isolation transformer which are just as common. I used 1:1 isolation transformers for the audio paths though.

  • edited April 2017
    Hi Steve...this is Paul "...pulling on your arm hard." Real hard.

    Thanks...and thanks again for the transformer.

    I hope to be at the Hamfest by 11:00 am.

    I'll be the guy with the Baofeng microphone searching for an honest hook-up circuit.
  • Paul, if you still haven't had any luck, I would be more than happy to come over and we can play for a little while.. We can get your Mic working as long as you have an external speaker hooked up.. ;) Let me know if you need it.. An optocoupler would work but it would require some circuitry that might just be too much to do for a simpler fix.

  • Aaron, this is very generous of you to offer, and I would indeed like to get your eyes on my 'visible radio' project and perhaps experiment.

    So far, I am trying to rely solely on the Baofeng combined speaker/mic...however I do have a small 8-ohm 'Mini-Speaker' that I purchased from Radio Shack if needed.

    The project may not be as 'pretty' however, I am stymied now and cannot proceed. I've soldered.. most of the wires and need some help only on getting the Baofeng speaker/mic to work...if at all possible. I don't mind opening it up and changing the connections...and will sacrifice the speaker/mic for the good of scientific investigation if need be.

    I would like to avoid blowing up the Ritron, however...

    I know you are busy every day and I would also be happy to bring my project to your shop...however...if you could spare me a few minutes in the next few weeks...that would be terrific...I know I can learn what is going on if I can just ask a few questions.

    Please let me know what works best for you and what will be the least disruptive to your professional and personal schedule.

    Aaron...this is really very kind of you.




  • edited May 2017

    Okay. I hung out with Paul this evening and we figured out the correct circuit with the Baofeng microphone for the Ritron that actually works. The problem with the actual circuit is the Microphone element itself. If you pull that out of the circuit and hook it up alone, the microphone element will actually pull the radio to transmit. KD2BID's findings were correct. KD2BID - Good job on your research!

    The Baofeng microphone must be modified. A trace must be cut and a wire soldered. You could hook up a switch to connect this back to use it on the Baofeng if wanted but I don't think it should be necessary..

    The wrong trace was cut at first. So if you decide to follow, please cut the correct trace..

    NOTE: PTT does not need to be connected to the microphone at all. Speaker and Mic both work.

  • When Aaron KC2NDA finished doing 'major surgery' on the Baofeng and we fired up the Ritron for the last of at least 15 or 20 experiments we conducted, I felt like yelling out "Eureka!"

    Kudos to Charles, KD2BID for your thorough detective work. You were on the right track.

    This project has helped me to learn a ton about electronics; circuit diagrams; trouble shooting and problem solving related to radios; re-kindled my soldering skills and I got to know many more helpful club members and Hams in our area.

    We could have abandoned the Baofeng, however that wouldn't have produced the fun of the learning new things and the exciting journey of problem solving.

    Thanks to Aaron, I also avoided having to drill more holes in the plexiglass (ugh)...and making the 'visible radio', as Dave, K2JLV has dubbed my project, less attractive.

    Thanks to all involved.

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