TopBand: Elevated Radials

[N6DX@aol.com]

Hi Roy,
Keep in mind that the vertical radiating section should carry the most
current hence the top hat.  I believe  that aluminum tubing topped with a
good coil and a hat or a flat-top is preferred over a helical winding.  Don't
worry if the bandwidth is narrow.  With a short antenna, if your bandwidth
isn't narrow it's probably because you have losses.  Regarding loading coils
on the radials, you can put a coil in each radial but it's much harder to get
them exactly matched for cancellation.  I use a big coil with all the short
radials connected at one point.  In some cases we use a single beam element
elevated 5 or 10 feet off the ground for the radials and add enough coil for
resonance.  If the vertical is more than a quarter wavelength it takes less
coil to resonate it.  For coil material we use the outer braid of coax.  It
is easily wound on polyethelyne drain pipe.  RG59 is better than #10ga copper
and not quite as good as 1/4" copper tubing.  Old RG8 works great. This is
more important on the lower bands simply because you need more inductance and
it becomes harder to make a very low loss coil.  Let us know how it works.
 73
Darrell, N6DX@aol.com

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