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CM Choke - Coax Type Matter?

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by N7AY, Mar 2, 2021.

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  1. N7AY

    N7AY Premium Subscriber QRZ Page

    In searching I see a variety of 50 ohm coax types being used in various ferrite toroid/bead CM choke designs.
    Is there any electrical significance to which type of 50 ohm coax is used or is it solely a physical concern, small enough to fit closely to the ferrite, bends enough, will support the number of turns though the toroid that are needed?
  2. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    Electrically, type does not matter, as long as it is of reasonable quality.

    -"Minimum Bending Radius" is a key limiting factor for any coax to avoid damage and compromising impedance, shorting and RF leakage. Refer to manufacturer's spec sheet. Don't "assume" one radius spec applies across any give coax type.
    K0UO and KU3X like this.
  3. WA7ARK

    WA7ARK Ham Member QRZ Page

    Avoid coax with the soft, PE, thermoplastic center conductor. It can short the center conductor to the inside of the shield.
    K0UO likes this.
  4. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    As long as Minimum Bend Radius and Power/Heat Dissipation ratings are not exceeded, there is no reason such coax cannot be used.
    KU3X likes this.
  5. WA7ARK

    WA7ARK Ham Member QRZ Page

    I would just use the Teflon stuff, like RG-303 or RG-400. I have a spool of slightly smaller white, Teflon, 50 Ohm coax that looks like this when wound onto a 2.4inch core.
  6. WA4SIX

    WA4SIX Ham Member QRZ Page

    A stranded center is key to not deforming the coax. I bought a short spool of RG400 just for baluns.

    K0UO likes this.
  7. N7AY

    N7AY Premium Subscriber QRZ Page

    Thanks for the help!

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