I'm in the process of putting up one of those right now.
I'm using No. 18 insulated wire from Wireman, not because this is the best
choice in all respects but because I don't have 4 tall trees ideally
located that will support No. 14 wire, which is ideal. It will be about
280' tip to tip.
I use the dacron black stuff for guying the 12M Spiderpoles and other
places where rope etc is needed. I used it for the dipole support I
presently have and it is satisfactory. I also use line tighteners on the
guy lines.
I have no balun when using the Icom AH-4 remote auto tuner, but will put a
choke between it and the radio. I also have the choice to use a balun with
a LDG RT-100 remote tuner and may do that instead. Baluns from Balun
Design seem to work well. I can use these tuners because I seldom run more
than 5 watts and never more than 100.
A helpful ham who understands this stuff was kind nough to run an EZNEC
model for me, with these results:
An EZNEC model of your antenna using #18 having insulation of Er=4 and
0.01" thickness and fed in the middle of one side show these input
impedances :
3.525 MHz 100 -j4 ohms
7.025 MHz 275 +j80 ohms
10.110 MHz 250 - j400 ohms
14.025 MHz 260 -j25 ohms
18.075 MHz 560 +j500 ohms
21.025 MHz 430 +j100 ohms
24.890 MHz 550 +j360 ohms
28.025 MHz 280 +j190 ohms
I would probably go with a 4:1 balun if I elect to go with the RT-100.
I'm not going to worry about springs or any of that. The Spiderpoles are
flexible and flimsy enough to handle it, I think. If not, we'll get some
more No. 18 and try again!
According to EZNEC, this will be a very good antenna for what it is, a big
improvement over the 130' dipole I've used most of this year.
GL
73 de W6OGC Jim Allen
On Mon, Dec 29, 2014 at 12:50 PM, Curron <kb3drw@msn.com> wrote:
>
>
> Need some help folks...
>
> I would like to get some input on building an 80 meter sky loop
> antenna that I will use on 80 and other bands with an antenna tuner. I have
> some nice tall pine trees to run the corners to and I plan on joining the
> loop
> to the house with 450 ohm ladder line. Just under the edge of the house I
> will
> install a balun and bring it into the house with low loss coax. Please
> make any
> comments or offer any advice you can. I am hoping to learn from your
> experiences. Some questions I have are:
>
> - What kind of wire should I use for the
> loop antenna
>
> - What type of rope that will hold up to
> the UV and time (so much just falls apart these days)
>
> - What balun, 4:1, 1:1 ?
>
> - Is 450 ohm feed ladder line the best to
> use? This part will be about 80 feet long. Will this length be a problem?
>
> - Has anyone ever had any issues using
> delrin for the insulators? Is there a better?
>
> - I am thinking about placing a screen door
> spring on each corner to allow the trees to sway in the wind… anyone ever
> tried
> that. Or should I just counter weight to opposing corners of the loop?
>
> - How’s the best way to protect this
> setup from lightning?
>
> Thanks in advance for any help!
>
>
>
> 73
>
> Don kb3drw
>
>
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> TenTec@contesting.com
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>
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