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G8MNY > TECH 13.06.05 12:20l 38 Lines 1152 Bytes #999 (0) @ WW
BID : 49460_GB7CIP
Read: GUEST OE7FMI
Subj: Coax Sleeve Balun
Path: DB0FHN<DB0MRW<DB0WUE<DK0WUE<DB0RES<ON0AR<GB7CIP
Sent: 050613/0904Z @:GB7CIP.#32.GBR.EU #:49460 [Caterham] $:49460_GB7CIP
From: G8MNY@GB7CIP.#32.GBR.EU
To : TECH@WW
By G8MNY (Updated Dec 04)
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 ¬ 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.
ÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
BALANCED ÚÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
BÄÄÄ) UNBALANCED FEEDER
BÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
ÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
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 ³ .'.
³ / \
Low³...-' '-.....
ÀÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄ F
Fo
Why don't U send an interesting bul?
73 De John, G8MNY @ GB7CIP
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