[TenTec] Antenna help

Jim Allen jim.allen at longhornband.net
Tue Dec 30 12:04:11 EST 2014

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.


73 de W6OGC  Jim Allen

On Mon, Dec 29, 2014 at 12:50 PM, Curron <kb3drw at 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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