> My questions are these - is a
> relatively flat curve to be expected, or a sign of something wrong?
A flat curve is to be expected and it's a sign something is wrong.
And that something is that you do not have nearly enough radials in
your ground system. Your radials are on the ground. Such a ground
system should be augmented with about 10 times the number of radials
you have, but they don't need to be 70 feet long. 50 feet is okay,
but you need many more. The sign your antenna is efficient will be a
narrow R and X sweet spot. R should drop down to around 14 ohms and
(depending on the length of the driven element) X should hit zero over
a few kc. If there are structures around re-radiating you may not see
0 X; it may dip down but not get to zero.
73
Rob
K5UJ
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