[TowerTalk] Inverted L for 160 Meters

[Tim Duffy K3LR]

Hello Tom:

Here is an easy antenna that I built last winter for 160 meters. It is
simple to build and works very well. I posted this to the TopBand reflector
last December and many operators built this and say it works great.

December 2006:
For the ARRL 160 contest a few weekends ago, I needed a quick and easy way
to get on TopBand from my Oklahoma QTH.

I am in a very antenna restricted area and my back yard is only 50 ft deep.

I purchased 450 ft of #16 insulated THHN  wire (about $45.00). I cut three
132ft lengths. I soldered one length on to the center of a SO239 chassis
mount (UHF female) connector. The other end of this wire I curled around for
a string. The other two 132 ft pcs I soldered to the SO-239's outside (using
2 holes) points
for radials.

With a fishing pole I casted up over the back yard tree that stands about 50
ft tall. I proceeded to pull the curled end with string over the tree. I
pulled the first 20 feet of the antenna (coming from the SO239) vertical
with another string to the chimney of the house. The two radials were pulled
out away from the feed point. The antenna went on top of the tree and down
the other side forming a upside-down "U".

I hooked about 40 feet of RG8X to the feedpoint (also a 4 ft ground rod)
coiling about 20 ft in a 1 ft diameter bunch to form a current choke at the
base.

Inside I hooked up the Icom IC765 and the VSWR was 1.1:1 at 1830 without
trimming.

The antenna worked great! With a part-time 100 watt effort I worked 46
states and 7 DXCC countries. Not bad for a simple 160 meter antenna.

73!
Tim K3LR

http://www.k3lr.com



-----Original Message-----
From: towertalk-bounces at contesting.com
[mailto:towertalk-bounces at contesting.com] On Behalf Of Tom Crothers
Sent: Sunday, October 14, 2007 10:02 PM
To: towertalk at contesting.com
Subject: [TowerTalk] Inverted L for 160 Meters

Hello all,

 

There's an article in the October 2007 QST by Steve Ford entitled "Waiting
for the Sun".  For those of you who read the article, and may have some
information/answers, I have a few questions regarding the construction of
the 160 meter inverted L antenna that is shown in Figure 3 of the article:

 

 

*        Do I understand correctly, that C1 in the diagram is a simple
variable capacitor that ranges from 100 pF to 800 pF?  (I found one, and
purchased it)  

*        Is it for tuning the antenna for minimal SWR? 

*        How did the author arrive at the wire length of 165 to 175 feet?  

 

I know these are pretty basic issues/questions, but I built this antenna
today.  I want to be sure I've built it correctly, and moreover, I want to
be sure I understand how to tune it correctly.  

 

*	Right now, I can get a minimal SWR of 3:1 at 1.810 MHz by tuning the
variable capacitor for min SWR. 
*	I don't have any radials installed at present.  The coax braid is
grounded to my tower ground (three 8 ft rods bonded together) 
*	I plan on adding some radials (laid on the ground) tomorrow.  Should
they be of any particular length to perform optimally? 

 

I've emailed Steve Ford addressing the above, but I also wanted to see what
the folks at TT think.

 

Thanks all.  

 

73,

 

Tom

W8KF

 

 

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