5 thoughts on “Uniden Bearcat 680 modulation adjustment”

  1. Your video concerning the modulation mod is good and has good results. Being an amateur at mods it would have been nice to SEE actually how you did it.
    How about a wattage increase. How much gain can be had without decreasing modulation.

  2. Thanks in advance. DTB radio describes a mod for BC680

    AMC modification:

    CAREFULLY cut the trace between D240 and D241. Its a very narrow trace, so be CAREFUL!
    Solder a 10k – 15k resistor between the diodes, basically jumping it across the cut you just made.
    CAREFULLY remove C291 (next to D240), and replace it with a 4.7uf 25v cap. This is a double-sided board and easily damaged so be CAREFUL!

    I have noticed that C291 is already 4.7/25v.
    Do you see any reason to add a 10-15k resistor to your mod?


    1. HI DOn, I havn’t changed the capacitor and I haven’t added a resistor, but I have cut the amc trace and it brings up the transmit audio very much. I have a few of these radios in a trucking fleet and they all talk and sound good. 10-4 driver.

    1. Thanks for the heads up. I believe I tried that and it didn’t have any transmit audio, but I will look into that. Thanks for the good info.

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