[TowerTalk] Inverted L Dimensions

[Anthony J. Cioffi (N2KI)]

This is a design I found and it works right from the start. I built it for 160 meters using 14 gauge stranded bare copper and
have great results. The feed point is made from aluminum L stock.  Drill a hole for a panel mount SO-239(not chassis) to fit.
Do not directly connect the vertical element to the SO-239.  The first strong wind will rip it apart.  To address this,
anchor the vertical element to the tree using an insulator, rope and then a lag eyebolt into the tree.  This will secure your
vertical end so you can safely solder a wire to the center pin of the SO-239 and the wire without straining the feed point.
Connect the elevated (10') counterpoises to the aluminum plate with a terminal lug and self-tapping screws. Extend the
counterpoises and support them along the way by affixing them to a tree with electric fence post insulators.  They are
perfect for this application.  I have attached photos of the feed point idea and the insulators.  I suspect the server strips
the attachments. Scott, I emailed you direct so you will have the photos. 

Here is a copy of the text from the document, by WA2VUO.

The Inverted "L" Antenna

So, you REALLY want to get on the 160 Meter band, but the neighbors won't let you run your 250' long dipole over their
swimming pool? And, you say that the State DOT looks down on your attempt to tie the other end across the State Highway?
Well, fear not, as there is a compact solution to your MF antler woes, and it is an Inverted "L". [It can also be cut for 80
or40].

The Inverted "L" is a 1/4-wave Marconi, fed against ground or a counterpoise such as radials. The antenna displays a low feed
impedance, which allow you to feed it directly with 50-ohm coax cable. The vertical section should be as high as possible,
with the remainder of the antenna run horizontally to a support, such as a tree or a mast. The antenna is fabricated from
wire, with the heavier the gauge the better. [The larger the wire diameter, the wider the bandwidth]. One method of
installation would be to use a mast as the vertical "wire", with the horizontal section firmly bonded to the top of the mast.
The wire is cut to a resonant 1/4-wave length, based on the formula:

L(Ft) = 234/F(MHz)

If your ground is REALLY good, like your house is on stilts over the ocean, a counterpoise won't be needed, but for our GREAT
ground here in Western NY, figure on using at least one counterpoise, if not a few. The length of the counterpoise wires will
be cut to a 1/4-wavelength by the formula:

L(Ft) = 246/F(MHz)

Basically, the counterpoise should be high enough to not get in the way, but could be as high as your installation allows.
Mine is run around the base of the house, just below the siding, except around the back door. At that point, I ran the wire
under the bottom of doorframe. The wire I used is #18 stranded insulated hook-up wire.

CHARTS
Well, any antenna discussion is not complete without a chart of some sort, so here are the dimensions for an Inverted "L",
listed in tabular form:

Frequency 	Radiator Length 	Counterpoise Length
1.85 MHz 	126.5' 		133.0'
1.95 MHz 	120.0' 		126.2'
3.60 MHz 	65.0' 		68.3'
3.90 MHz 	60.0' 		63.1'
7.15 MHz 	32.7' 		34.4'



 Anthony - N2KI