[TowerTalk] Inverted L for 160 Meters

Mon Oct 15 12:49:57 EDT 2007

Chet:

     I, too, used a similar three-wire inverted L as my first antenna on Topband back in 1998.  The vertical wire went up into an oak tree about 45 feet and bent over to another tree on the far side of the bak yard.  The remaining two wires were laid on the ground about 90 degrees from each other (property boundaries made me do it that way.) I worked the ARRL 160M test that winter and had a blast.  

     Since then I've put in about a half mile of scrap wire radials in the grass around the base of the oak tree.  The Inv L is no longer there (I shunt feed my tower now) but the radials are available for use with another vertical or for K9AY's array if I get ambitious some year.

73 de
Gene Smar AD3F

From: Tim Duffy K3LR <k3lr at k3lr.com>
Date: 2007/10/15 Mon AM 09:38:27 CDT
To: 'Chet Moore' <ChetMoore at cox.net>
Cc: towertalk at contesting.com
Subject: Re: [TowerTalk] Inverted L for 160 Meters

Hello Chet!

The radials are laid on the ground. They self bury after a few months.

I was amazed how well this simple antenna worked. The efficiency is really
helped with the full size 1/4 wavelength radiator. 

My NEC model comparison indicates that the gain is only 5.1 dB less than a
fully vertical 1/4 wavelength element with 60 1/4 wavelength ground mounted
radials!

CU on 160!

73!
Tim K3LR 

-----Original Message-----
From: Chet Moore [mailto:ChetMoore at cox.net] 
Sent: Sunday, October 14, 2007 10:51 PM
To: k3lr at k3lr.com
Subject: Re: [TowerTalk] Inverted L for 160 Meters

Tim,

I put this e-mail in my hints and kinks file.  The two radials.......were 
they laying on the ground or elevated ?  from the sound of the space 
available,
it sound like they were probably laying on the ground.   This article by 
itself should lead to a large number of 160 enthusiasts who thought they 
could not get a 160 antenna on their lot to give this a try.

Thanks for sharing

73

Chet N4FX

----- Original Message ----- 
From: "Tim Duffy K3LR" <k3lr at k3lr.com>
To: "'Tom Crothers'" <TCrothers at columbus.rr.com>; <towertalk at contesting.com>
Sent: Sunday, October 14, 2007 11:15 PM
Subject: Re: [TowerTalk] Inverted L for 160 Meters

> 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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