On 2013-10-01 14:08, Bill Stewart wrote:
Good afternoon all,
The vert. section is
abt 55 ft & the rest is nearly flat horizontal. Total length is 130
ft/6 in. I am using a
4 wire c-poise abt 9 ft high of which none are directly under the
horiz. section.
Each wire is abt 135 ft long. The min. SWR is abt 2.9:1 at 1833 khz.
The SWR
This is exactly what you would expect. It corresponds to a drive
impedance
of something like 18 ohms, about right for a top loaded 55 foot
vertical.
You will need to put a shunt capacitor of about 2400 pF across your
coax,
and then increase the length of the L until you get the resonance to
1833 kHz.
I currently have a top loaded 60 foot vertical and this is very similar
to my situation. You will find that after proper matching, the
bandwidth
is really quite narrow, indicating reasonable efficiency.
You should probably add a common mode choke at the feedpoint if you
don't already have one.
Rick N6RK
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Topband Reflector
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