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Thread: How to choke puck mount?

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    How to choke puck mount?

    Is there a common method to choke coax at a puck mount? I have never ran a lot of power before and I've always just choked under the headliner. Would I have less RF in the vehicle if I choked on the roof then hooked up to the puck on the outside? Any thoughts?

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    I would not recommend using an air coil in a vehicle, the metal next to it will throw off its resonant frequency and most people don't have either the knowledge or equipment to account for this.

    I would recommend the slide on ferrite beads, if you have access to the end of the coax. I use shrink tubing to hold them in place when I use them, although zip ties that aren't over tightened work well as well. If you have no other option, snap on ferrite beads work as well, although they tend to be larger in diameter because of the snap on mechanism. With ferrite you can use as many beads as you want. I would recommend six or more. The specific beads you use are dependent on the diameter of the coax.


    The DB

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    SkoalCracker (07-19-2022)

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    Quote Originally Posted by The DB View Post
    I would not recommend using an air coil in a vehicle, the metal next to it will throw off its resonant frequency and most people don't have either the knowledge or equipment to account for this.

    I would recommend the slide on ferrite beads, if you have access to the end of the coax. I use shrink tubing to hold them in place when I use them, although zip ties that aren't over tightened work well as well. If you have no other option, snap on ferrite beads work as well, although they tend to be larger in diameter because of the snap on mechanism. With ferrite you can use as many beads as you want. I would recommend six or more. The specific beads you use are dependent on the diameter of the coax.


    The DB
    I ended up going with 10 of these beads on lmr400.
    DX Engineering DXE-CB31-500-10 DX Engineering Ferrite | DX Engineering
    I'm guessing that might be somewhere between 500 and 1500 ohms and should... maybe be resistive? I honestly have no real idea and just doing something rather than nothing. If I can get my ground loss low enough, this choke might be enough.

    Now I'm running into rising swr readings as amp output increases. I'm kind of new to CB amps and the thought of signals exiting an amp that aren't on the desired frequency didn't even cross my mind. I'm probably going to try a low pass filter and see if it makes a difference.

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    I've no idea why you'd choke a mobile radio. You say you're not running power; therefore your pacemaker is not apt to be disturbed by any RFI in the cab. Not knowing what length of coax is being used, again I can't fathom why a choke is deemed necessary in a mobile. Of course there are exceptions; your 1/4 λ antenna is puck (magnet) mounted at the tail of your 53' trailer then another 18' to your cab mounted radio you've a mighty long radiating antenna, your coax. There really isn't a minimum length to coax; yes, some will argue. If a choke is absolutely deemed necessary, by you, choke it at the radio.

    I put air chokes (fugly baluns) on all my base station antennas. Keeps the neighbors happy and with near 25' x3 coax lengths inside the shack I don't hear any ring tones, or visions of goblins.
    Last edited by Alabama Buckeye; 07-28-2022 at 04:35 PM.
    All answers are opinions and may, or may not be technically correct.

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    Quote Originally Posted by Alabama Buckeye View Post
    All answers are opinions and may, or may not be technically correct.
    Thank you for your honesty

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    Quote Originally Posted by SkoalCracker View Post
    Thank you for your honesty


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    Quote Originally Posted by JesseJamesDallas View Post
    I'm honestly not certain if that guy was serious or just screwing with me.

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    Dave Casler, KE0OG, sez, "...a choke is never needed until it is..." That is to say, if you know RFI is created and is an issue then install a choke. I've found "air chokes" have absolutely no influence of receiver noise. That includes a Fugly Balun at the antenna and a dozen clamp-ons at the radio.

    And perhaps were you to use double shielded coax, braided and foil, you may reduce generated RFI all together. There is one supplier that has such RG-8X; it's a bit more $pendy.

    If your pacemaker is operating on the same frequency as your broadcast; you might want to install a choke. But a few clamp-ons is near useless. Save for the "feel good" sense.

    Last edited by Alabama Buckeye; 07-28-2022 at 04:49 PM.
    All answers are opinions and may, or may not be technically correct.

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    Quote Originally Posted by Alabama Buckeye View Post
    Dave Casler, KE0OG, sez, "...a choke is never needed until it is..." That is to say, if you know RFI is created and is an issue then install a choke. I've found "air chokes" have absolutely no influence of receiver noise. That includes a Fugly Balun at the antenna and a dozen clamp-ons at the radio.

    And perhaps were you to use double shielded coax, braided and foil, you may reduce generated RFI all together. There is one supplier that has such RG-8X; it's a bit more $pendy.

    If your pacemaker is operating on the same frequency as your broadcast; you might want to install a choke. But a few clamp-ons is near useless. Save for the "feel good" sense.

    I'm assuming you actually do have a pacemaker?

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