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  • Coax Sleeve Balun

    From G8MNY@21:5/101 to WW on Thu Sep 5 23:05:15 2019
    G8MNY TECH 05.09.19 03:07l 39 Lines 1216 Bytes #365 (0) @ WW
    BID : 20246_GB7CIP
    Subj: Coax Sleeve Balun
    Path: OK0NBR IW0QNL JH4XSY JE7YGF GB7CIP
    Sent: 190905/0559Z @:GB7CIP.#32.GBR.EURO #:20246 [Caterham Surrey GBR]
    From: G8MNY@GB7CIP.#32.GBR.EURO
    To : TECH@WW

    By G8MNY (Updated Dec 04)
    (8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
    This type of balun is to be found in most textbooks & many aerial designs. It is a 1:1 balun & does not alter the impedance.

    Balun is made from ¼ wave lengths of scrap coax (longer needed to cover the fatter outer) braid or pipe over the top of the feeder. It is electrically connected to the coax braid 1/4 wave from the balanced feeder connections.

    ─────────────┐
    BALANCED ┌────────────┴───────────────────
    B───) UNBALANCED FEEDER
    B───┴────────────┬───────────────────
    ─────────────┘

    This works by hiding the unbalanced outer aerial connections from the outside world so it can't radiate.

    In practice I recommend heatshrink sleeving & heat glue it used to seal the add outer section.

    Common mode Z is only high at the resonant frequency, where it eliminates any outer feeder current on the unbalanced coax.

    Z
    Hi │ .".
    │ / \
    Low│...-' `-.....
    └───────┬────────── F
    Fo


    Why don't U send an interesting bul?

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