On 10/17/2020 9:38 AM, Kim Elmore wrote:
I have a F12 Sigma 80 antenna, which is an OCF vertical dipole with
inductive loading at the feed point and a hairpin match. While it
*requires* a common-mode choke at the feed point, it works very well for
DX. On stateside contacts, I think its radiation angle is too low and
performance for anything within about 400 mi is much worse than for my
inverted V with (apex at 40 ft). On DX, though, it does MUCH better than
the inverted V.
Verticals shorter than about 3/4 wavelength, by their nature, have a low
radiation angle. It has nothing to do with the design of the F12 antenna
other than it's height. This is made clear by a study of the link I
posted for my study of vertical antennas and horizontal antennas, and by
study of the ARRL Antenna Book, the ON4UN book, and the Antennas chapter
of the ARRL Handbook.
I have no radials beneath this antenna.
By it's design, no radials are needed.
I know a friend is buying a Greyline antenna for his QTH. They initially
look a bit pricey, but I've not actually seen one, so I don't what the
build quality is truly like. Assuming it's build quality is pretty good,
and assuming it has a good CM choke,
From what I see on their website, that may not be a good assumption.
there's no reason why it shouldn't
perform relatively well given the constraints. Certainly better than no
antenna at all!
This last sentence is the key -- if you're stuck in an HOA, it's better
than nothing.
73, Jim K9YC
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