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G8MNY > TECH 23.02.04 23:58l 28 Lines 932 Bytes #999 (0) @ WW
BID : 44980_GB7CIP
Read: DB0FHN GUEST OE7FMI
Subj: Coiled Coax Choke Balun
Path: DB0FHN<DB0RGB<DB0MRW<DB0ERF<DB0FBB<DB0BI<DB0NOS<DB0EA<DB0RES<ON0AR<
IK1ZNW<GB7CRV<GB7CIP
Sent: 040223/2205Z @:GB7CIP.#32.GBR.EU #:44980 [Caterham] $:44980_GB7CIP
From: G8MNY@GB7CIP.#32.GBR.EU
To : TECH@WW
By G8MNY (new 02/03)
A very practical Balun for aerial work is the choke type.
All it is, is a slightly shorter than a 1/4 wave of coax tightly coiled up as
close as possible to the aerial feed point, & tapped the boom making sure the
coil at right angles to the dipole & does not couple to it! The rest of the
feeder is tightly tapped to the boom to reduce any outer feeder currents &
maintain the feeder out free from RF pickup.
@_______@_________@_________@_________@______D______________R
Boom | | .------------/\/
Stub | |³ \/ Coil
Mast | |³feeder
| |³
@=directors
D=Dipole
R=reflector
This type of balun can be used in most cases, especially TV & FM designs that
have omitted a balun for cheapness.
/QSL
73 De John, G8MNY @ GB7CIP
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