Topband: Inverted L matching
tom at telemetry.demon.co.uk
Sun Mar 5 13:39:35 EST 2006
Thanks to all those who responded on the subject of matching 160 metre inverted-L antennas. As expected, everyone does it differently!
KU8E uses a 1.78:1 UNUN and has problems
N2CU uses a 2.25:1 UNUN with good results
W1TO recommends no matching network unless lots of radials
K9UWA recommends no longer than a true 1/4wl and a 2:1 UNUN
WB3AVN uses no matching network but prunes antenna length for good match
N4OGW uses a slightly shorter than 1/4 wl and a 'hairpin'(?) coil across feedpoint
VE3CSK uses a tapped air cored inductor - presumably antenna is somewhat shorter than 1/4 wl?
W0ALC uses 170' and series C
K9AY uses 1800pF across feed point with antenna a few feet longer than 1/4 wl - or parallel inductor with antenna slightly shorter than 1/4 wl
G3PQA believes there is some DX advantage in having some horizontal as well as vertical polarisation so sets the current max at half way up the vertical section.
K8GG says 5/16 wl tuned by 400-450pF in series. 5/8 wl is too long because it has near 1/4 wl horizontal section with near half energy radiated upwards.
K2AV recommends a multi-tapped UNUN.
Thanks again and 73
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