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Amped up

Discussion in 'CB Radio Modifications' started by Timmydav, Dec 6, 2018.

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  1. Timmydav

    Timmydav Member

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    So today I installed a rfx 85 in my pc 68 elite. It keys up about 3 watts but only modulates up to about 35. I've heard they will turn out about 75 pep so what
    Do I need to do to pump this little radio up
    .


     

  2. sonoma

    sonoma Sr. Member

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  3. Tallman

    Tallman W9WDX Amateur Radio Member, KW4YJ EXTRA class

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    Needs more drive.
     
    Shadetree Mechanic likes this.
  4. Timmydav

    Timmydav Member

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    A bigger driver in the radio
    Itself? Ya I took it right from cb tricks and I haven't done the cap mod yet.
     
  5. Handy Andy

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

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    Several questions here...

    You installed a RFX 75 or RFX 85?

    THERE IS A NEWER ONE - THE RFX 95 - please be sure about this...

    What did you turn the radio down to - before you installed the RFX unit?

    If the radio was left "Stock" it only needed 3 to 4 watts from the radio so if you did any mods to the radio BEFORE this - you'll need to undo them - especially if you did a Swing mod using JP36 method for Cobra 29 models.

    The Driver on the radio has to have it's drive level set to drive the RFX unit.

    THIS IS FOR NON-HD RFX-85 models!
    RFX85NOTHD.jpg

    See bottom left corner - JV17/JP36 Mod location...

    So if you did a mod to set the swing at 1 - 1/2Watt and go up from there - reverse it out. Then Tailor the "resistor" part of the Resistor/Cap swing combo to THE RADIOS' DRIVER to make the carrier climb to about 10 watts - it needs that as a MINIMUM in order to work properly. IF you wanted swing an amp - do NOT use the RFX to do this - get a separate external amp or modulator instead - the RFX can't work as a modulator - at least not without more help.
     
    #5 Handy Andy, Dec 6, 2018
    Last edited: Dec 6, 2018
    Shadetree Mechanic likes this.
  6. Handy Andy

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

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    There is also an RFX HD (High Drive) unit that uses less wiring and I wonder if you have that instead?
    It only uses one MOSFET...and a BIG relay...

    AND - YOU DO NOT REMOVE THE FINAL

    PDF attached...
     

    Attached Files:

  7. Timmydav

    Timmydav Member

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    So I went back and rechecked all my connections found aloose wire on the antenna hookup now itll do 20 on key up and seing right up over 75 pep!. Im gonna go ahead and put the cap and resistor in to bring it back down tune it up,and were good to go. I really appreciate your input guys.thanks
     
  8. Shadetree Mechanic

    Shadetree Mechanic 808 On The North Side of Dover

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    Are you using an SWR meter I hope?
     

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