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Uniden PC68LTW Lower Side Band Modification?

Discussion in 'CB Radio Modifications' started by TwoToned, Jun 13, 2018.

  1. TwoToned

    TwoToned New Member

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    Anyone know how to Mod the Lower Side-band, for the Uniden PC68LTW? I’d like to try this, but as a shade tree technician ; I was hoping someone more experienced could walk me through the process. I know it can be done cause this video shows it post mod (). I’d like to make the RF knob a fine tune knob too. If anyone knows how to perform this mod I’d love a detailed explanation and walk-through of the mod; pics would be awesome, and video amazing. Although, any help would be very cool .




    Thanks
     

  2. midnight special

    midnight special Well-Known Member

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    low channels and lower sideband is 2 different things,,,
     
    Captain Kilowatt likes this.
  3. sonoma

    sonoma Sr. Member

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    you have to have a channel kit to get lower channels. it will not be lower SSB as you asked. so not sure if you really know what the shop did.
    anyway you have to have the channel kit and install it for lowers. Bells electronics is about the only place that would have the kit. . just like the echo board they put in the radio it has to be purchased to make the echo work..
    ever so often you can find an old expo kit to install for lower channels on this radio.
    it takes an S- kit for lowers.
     
  4. nomadradio

    nomadradio Analog Retentive

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    The channel kit for this radio has some drawbacks. The normal designation is type "S".

    You can install only upper or lower channels with this one, not both. That's what the "+" or "-" after the letter "S" indicates.

    The PLL chip that was used for this model was meant to be "channel proof". This kit did not show up on the market until almost ten years after the radio hit the market. Took them that long to figure out a way to do this.

    Even though you can't modify the PLL chip's circuits, you can modify the radio's internal frequencies to change the channel coverage. In particular it changes the receiver's intermediate frequency and eliminates part of the receiver's normal filtering ability

    The main drawback will be the receiver's reduced ability to reject strong signals on other channels.

    But you will have only AM mode on this radio, no matter which channels it covers.

    USB is upper sideband. LSB is lower sideband. This refers to a method of splitting a CB channel in half, more or less, by removing the carrier from the radio's transmit signal. The receiver used for sideband has to put the carrier back in to get the voice signal back. A sideband transmitter heard in an AM-only receiver sounds like Donald Duck with a sock in his mouth.

    73
     
  5. loosecannon

    loosecannon Sr. Member

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    just seconding what Nomad is saying here.

    using that expo kit changes the performance of the radio, and i believe involves cutting a trace to the If crystal.

    I hated that mod, but maybe some like it.

    either way, it's an AM only radio, and i can't see much benefit from a fine tuning control.
    LC
     
  6. TwoToned

    TwoToned New Member

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    Thank you for clearifying.
     
  7. TwoToned

    TwoToned New Member

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    Okay, I was thinking they put LSB channels, but I’m understanding that it’s extra channels. I appreciate your feedback.
     
  8. TwoToned

    TwoToned New Member

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    I see. It sounds like a mod that’s different than what I was thinking of when I saw it. Are there many folks running on the extra channels? I’m assuming these are illegal channels. Thank you for the detail response, I appreciate it.
     
  9. TwoToned

    TwoToned New Member

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    I agree the fine tune doesn’t make since without SSB. Thank you for helping me with this notion I had.
     
  10. Shadetree Mechanic

    Shadetree Mechanic 808 On The North Side of Dover

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    Welcome to WWDX!
     
  11. Handy Andy

    Handy Andy Do Your Research First, Then Decide...

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    I've had to de-convert these PC68/66 series as well as TRC427's (9106PLL) back to ordinary radios because the guy wanted the EXPO kit installed in a PC78...

    Now that I know you didn't mean a "LOWER SIDE BAND" conversion - you mean a Lower channel conversion, heres' what I got...

    First, make a plan - locate the area it's going in...
    PC66XLChannelMod.png

    Then review the instruction sheet and install the parts...
    PC66XLChannel.png


    Be sure to do up the cap for the main PCB Xtal - that 22pF.

    In this case, they "trimmed" at C111 installed a VARI-CAP a variable capacitor - to re-align the main PCB Xtal and the EXPO kit one together so they match on the NICKLES (the 26.965 versus 26.960 - kinda thing)

    PC66XLVCO.png

    That's about all I can do for you.

    Regards!
    :+> Andy <+:
     
  12. TwoToned

    TwoToned New Member

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    This is awesome! Thank you!
     
  13. Handy Andy

    Handy Andy Do Your Research First, Then Decide...

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    Don't thank me,

    Thank Bennie at CB Tricks.
     
    midnight special likes this.

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