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BTECH UV-2501+220 Transmit Audio Issue

Discussion in 'Radio Circuits, Repair & Performance' started by NE8SC, Feb 17, 2018.

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  1. NE8SC

    NE8SC Ham Member QRZ Page

    I have a Gen 1 BTECH UV-2501+220 that I purchased when they first came out. I used it in my car for about a year and received feedback the transmit audio level was low. I would all but yell directly into the mic. I did the mod with opening up the mic hole with minimal results. I contacted BTECH hoping to get an answer but no luck. I opened up the radio and there are two trim pots on the board. In my Alinco 220 radio, I had to open it up and dial down the transmit audio because it was to high. I am thinking that maybe on of them is audio level and the other deviation but without a schematic, no telling.

    Now to my question or hope, I am posting here to see if anyone out there might know or experimented with this radio. I have taken it out of the car since I sold the car. I would like to use on my desk at work since I have a Comet CX-333 triband antenna on the roof to take full advantage of the antenna. Obviously, to use the rsdio, I can't be yelling in the office as my coworkers will not appreciated it.

    Any help will be greatly appreciated.

    73,
    Steve
    NE8SC
     
  2. ND5Y

    ND5Y Ham Member QRZ Page

    If this radio uses the same AT1846/RDA1846 transceiver chip as other CCRs then the two pots are probably for reference oscillator frequency and output power level. There is probably no way to increase the transmit audio besides factory alignment software, which isn't available outside the factory, or using a different mic.
     
  3. NE8SC

    NE8SC Ham Member QRZ Page

    Thanks for the quick reply. I am not sure which chip it uses but most likely it is. Since there are only the two pots, I will with your answer unless I hear differently. I know it was resolved in newer generations but the 3rd was a complete redesign. I thought maybe trying a preamp.
     
  4. KA9JLM

    KA9JLM Ham Member QRZ Page


    Do you have the radio set for Wideband FM ?

    That sets the max deviation level.

    upload_2018-2-17_18-8-13.png
     
  5. NE8SC

    NE8SC Ham Member QRZ Page

    I will have to check when I get home. I don't remember seeing that in the setup.
     
  6. NE8SC

    NE8SC Ham Member QRZ Page

    Checked this morning and yes, it is set to wide. I did see a post where a guy swapped out the microphone with a Kenwood mic and reported the audio was better. Haven't tracked down a Kenwood mic to test out yet. I must live in the Icom & Yaesu area.
     
  7. KA9JLM

    KA9JLM Ham Member QRZ Page

    Normally the BTech mics work fine.

    Maybe you can change the resistor for the mic element to give it more gain.

    I bought the new radio version because it has a mic gain setting, That was a big plus.
     
  8. NE8SC

    NE8SC Ham Member QRZ Page

    The big trick to changing the resistor is knowing which one to change and what to change it to. This is the part of amateur radio that intrigues me but I haven't dedicated enough time to it to learn more about it.

    Yes, the Gen 3 of the radio does have the mic gain in the settings. That's the price I paid for not waiting. I was in a hurry to get a small tribander for my small car. I ended up with a full size mono band 220 radio to go with my dual band radio.
     
  9. KA9JLM

    KA9JLM Ham Member QRZ Page

    upload_2018-2-18_11-41-41.jpeg

    It would be in the location of the 1 k shown above.

    The replacement value would depend on what value it has now, And the voltage on it.

    I would not decrease the value to much. A resistor wheel and O-scope would be good to use.
     
  10. NE8SC

    NE8SC Ham Member QRZ Page

    Okay, it looks like there are two resistors in series for a total of 784 Ohms.

    upload_2018-2-18_13-59-8.png
     

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