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G8MNY > TECH 12.07.03 23:16l 28 Lines 865 Bytes #999 (0) @ WW
BID : 5394_GB7CIP
Read: DF6DBF DB0FHN GUEST OE7FMI
Subj: Coiled Coax Choke Balun
Path: DB0FHN<DB0RGB<OK0PPL<RZ6HXA<HA3PG<IK1ZNW<EA7URC<GB7CRV<GB7CIP
Sent: 030712/2027Z @:GB7CIP.#32.GBR.EU #:5394 [Caterham] $:5394_GB7CIP
From: G8MNY@GB7CIP.#32.GBR.EU
To : TECH@WW
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 possable 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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