Topband: SHUNT FED TOWER ARCING
N4BAA - Jose Castillo
n4baa at cox.net
Fri Dec 30 19:02:21 EST 2005
Shunt fed my 75 foot 45G today.
On top at 88 feet is a FORCE 12 EF230/240 on 24 foot boom.
At 76 feet is a 5 ele KLM 20M mono on 42 ft boom.
Shunt wire is #18 spaced 42 inches from tower top and bottom.
Chunt Tap is at 42-ish feet up.
Was able to instantly put that baby at flat SWR at 1.830 with the motor
driven 1000 pf vacuum variable cap.
Impedance after driving it to a good SWR is roughly 40 ohms. Fired up
the AMP and hit is with 1300 watts...no issues....
Went to dinner...came back at 6:30 PM local...(cold weather..dry
air)...and although SWR still looks good....AMP is now tripping of line
for some reason.
There are coils on the FORCE 12 antennas but the KLM style 20M does NOT
have a coil across the driven elements....
Did not attempt any further "tweaking"....so...tomorrow should I TWEAK
the tap for a more 50 ohm tap?
Pull the shunt wire out even further to attempt to raise capacitance?
Thanks and Happy New Year...
Jose Castillo - N4BAA
More information about the Topband