[Antennas] Full-Wave 160 Inverted-L. . . . .???

[Terry Conboy]

At 03:15 AM 2008-03-03, Ron K9ze at aol.com wrote:
>But then for  some reason when I was out near the edge of our woods, that
>proverbial light  bulb came on, and I was standing there, wondering 
>if I should
>consider putting  up a full-wavelength Inverted-L for 160.  I have 
>the room for
>it - - -  should I use it ??  Up about 75' and out over the trees for about
>450'. . .  . .
>
>All the reading I've done the  past few months, I don't recall even mention
>of a full-wavelength  Inverted-L.
>
>Any chance someone might have some experience with this, or  maybe thoughts
>and/or information ??

Ron,

Anything longer than 3/8ths wavelength overall will have significant 
high angle lobes - fine for local QSOs, but likely to pick up more 
QRN on receive.  Some of the longer versions also have nulls and odd 
patterns at low angles.  For example, the 5/8ths wl version has nulls 
off both ends of the top wire at low angles.

The one-wavelength version has two high angle lobes with a null 
straight up.  There are also nulls at low angles broadside to the top 
wire (about 7-8 dB down at a 20 degree takeoff angle).  In addition, 
the signal off the open end of the top wire is down about 3-4 dB.  I 
can send you .jpgs of the patterns if you're interested.

As Chris WB5ITT mentioned, the feed impedance of the one-wl version 
is quite high (~ 8000 +j 3500 ohms with #14 wire).

A very popular approach (because it works quite well) is to use 175 
feet of total wire (i.e. up 75 feet and horizontal 100 feet,  about 
1/3 wl).  This gives a feedpoint impedance with about a 50 ohms 
resistive part and inductance that can be canceled with a series cap 
of about 270 pF.  The 2:1 SWR bandwidth is about 60-70 kHz and the 
low angle pattern is nearly omni (within +/- 1 dB).  The signal at 
the zenith is down 2-3 dB from the lower angle radiation, so you will 
still be plenty loud for short haul QSOs.

73, Terry N6RY