Bill,
I have used/built/designed many antennas over the years. I have had
a number of favorite antennas over along ham career. My only concerns
have been line loss due to SWR and launch angle. There have been a few
minor concerns like can I really put that thing up or not.
As I read your post, I infer that at the moment you are wanting to
add 160 meters to your capability. An antenna that I have used and liked
is the Twin Lead Marconi. It's a simple, cheap, and effective antenna. I
first saw it written up by Bill Orr years ago. The premise of the design
is that a quarter wave antenna driven against ground may not be the most
efficient antenna due to low radiation resistance. Therefore, raise the
radiation resistance by using the theory of a folded dipole. The folded
element raises the radiation resistance by a factor of 4 for 2 elements
as the impedance changes as the square of the number of elements. You
will still need radials, but your ground losses will decrease.
Another antenna that I have used successfully is the center fed 80
meter dipole fed with open wire feeder. With an antenna tuner it's an
all band antenna and losses are low because you are using open wire
transmission line. A 4:1 balun located near the point where you egress
your house allows you to transition to low loss coax, like LMR-400. I
use a variant of this during Field Day where one of our runs is 370+
feet long. This works fine with QRP; look for NA3DX in the rankings when
the ARRL publishes the FD results.
73,
Barry
K3NDM
On 10/1/2013 2:35 PM, bill.va...@gmail.com wrote:
My antennas for the past few years have been Alpha Delta Dipoles (an 80/40
and a 40-10) plus an 88 foot CFZ. When I began looking for a 160 meter
antenna I came across the Balun Design website which had a 9:1 unun plus an
article on using it with a single wire for all band performance. It sounded
to good to be true and you know the old saying ...... it probably is.
Remember that I have a 125 foot run of coax to a remote antenna switch up
the hill, in my little forest so line losses due to SWR are a major
concern.
Well, I ordered their 9:1 unun and hung a 124 foot inverted L set up at 25
feet. My experience tells me that it is worth the trouble to get it up
higher once the leaves are gone. The original radial system was 8 – 10 foot
radials, 2 - 15 foot radials and 1 - 30 foot radial.
Here are my initial findings:
160 meters: less than 3:1 across the band
80 meters: less than 4:1 across the band
40 meters: less than 3.5:1 across the band
30 meters: less than 1.5:1
20 meters: between 2.1 and 1.1
17 meters: between 2.5 and 2.1
15 meters: between 1.7 and 1.5
12 meters: 1.7 across the band
10 meters: less than 1.7 across the band
The above measurements were made with a Rigexpert AA-54.
After tweeking the radials, spreading them out more and adding a few more
longer radials I used K3-EZ software to sweep each band and got very
similar results. My goal was to get access to 160 which I achieved along
with access to all of the WARC bands as a bonus. I should mention that I am
using the 5kw version to allow for the added stress of a higher than
desired SWR and an amplifier on occasion.
The BalunDesigns.com website has the article linked from this page:
http://www.balundesigns.com/servlet/the-106/9-cln-1-9-dsh-1-unun/Detail
I have no interest in the company, etc. Etc.
Bill, VA3OL
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