[TowerTalk] 160m inverted l

[Terry Conboy]

At 06:27 AM 2006-12-08, ny6dx at aim.com wrote:
>  I am trying to figure the length of inverted l using #12 insulated 
> wire. I come up with 120 ft is this right?

That seems pretty short.  Even using the standard formula for a 
quarter-wave vertical, 234/f, you would get about 128 feet at 1.83 
MHz.  Generally, inverted L's require a bit more wire than a straight 
vertical.  Of course, this depends on local terrain and conducting objects.

The actual length depends to some extent on the ratio of vertical to 
horizontal conductors.  Here are some number I ran recently in EZNEC 
with #14 bare copper wire.  The 17 ohm ground resistance would be 
roughly what you might get with 4 radials.

Using #12 insulated wire will reduce the required length by about 
1.5%.  For example, the version with a 50 foot vertical wire would 
require a 82.75 foot horizontal wire for 132.75 feet total.

*-*-*-*

I ran these in EZNEC with #14 bare copper wire over Mininec ground 
with 17 ohms in the ground lead.  Note that "Z" includes the 17 
ohms.  Lengths are resonant at 1.83 MHz.  1:1 SWR referenced to 
feedpoint Z.  Max gain is in the direction away from the horizontal 
wire open end.

N.B. Using Mininec ground may overestimate the gain, especially for case 1.

Up   Out       Z    Gain, dBi   Gain at 20*  F/B at 20*  BW 2:1  GndLoss
  33  101.7   25.4  -2.3 at 35*  -2.9 dBi     2.7 dB      70 kHz    4.8 dB
  50    84.7   32.0  -1.3 at 29*  -1.6 dBi     1.5 dB      90 kHz    3.3 dB
  60    74.6   36.1  -1.0 at 27*  -1.2 dBi     1.1 dB     100 kHz   2.8 dB
131.1  0      54.4  -0.4 at 23*  -0.4 dBi     0            145 kHz   1.6 dB

73, Terry N6RY