Ed,
There is a FAR better way. Check out the design by VK4YB on his QRZ
page. It's a brilliant design, and works great, enabling him to set the
distance record on the band (in 2017, I think). The key element of the
design are dimensions that carefully place the current maxima in the 120
ft vertical section, and that doesn't need a radial system. It's a VERY
efficient antenna! BTW -- my NEC model didn't show pronounced
directivity in the direction of the loading wire that the author observed.
I took this as the starting point and tweaked the loading section to fit
on W6GJB's property, supported by redwoods. My tweaks were to break the
450 ft loading wire into several parallel wires. We measured feedpoint
Z, then used SimSmith to design a simple matching network with junkbox
parts. It plays extremely well -- Glen's worked VK4YB and a lot of
other stuff with it.
73, Jim K9YC
On 3/7/2023 10:45 PM, Ed Cole wrote:
My new 630m antenna will be a "T" vertical with four top wires formed by
80 & 40m dipoles. Feedline will be 40-foot 300-ohm open wire which will
be shorted for use as a vertical and use the same base loading coil.
Radial system will be wires lain in the lawn with staples from
DXEngineering (so lawn can be mowed). Start out with six radials but
can add to that over time to improve the antenna. The vertical will
also set up for 160m use by using a different coil tap.
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