de NØBEL, Kevin

Here begins my saga of getting on the "Top Band", 160 meters.

Its been about 7 years since I've changed anything on my antennas.   Before that it was 4 years.

Since my re-emergence on the bands this year, I've noticed 160m, and tried various things to make my wire antenna (off center fed dipole, which works 80-10), load on 160, to no avail.

As I started to plunge into research on a 160 wire antenna, I found an article I wrote about the design and installation of my OCF dipole, and I've included it on this site (under the title Off Center Fed Dipole, strangely enough).   In that article it gives me a hint as to why 160 fails entirely to load.   About half way down that article I report testing a commercial balun with the antenna analyzer and found that it fails to operate below 2.5Mhz, theoretical reasons why are given.  I hadn't remembered that, so this gives a reason as to why my current antenna won't load on 160.

 

I soon ran across this article about reduced half slopers:  http://www.iw5edi.com/ham-radio/files/160Half-Slooper-Antenna.pdf

I decided that this will be the basis for the design of mine.

It seems every time I do this I need to recreate the rough 3D model of my house, yard, fence and tower.   Perhaps this time around I'll put it where I won't loose it.  The model is simple and is just to help locate the fence, the fence corners, trees and other potential anchor points.   So thats my first task.

My second task is to choose the antenna modeling software.   With enough years intervening each antenna design project, I usually go through the choosing process again, since the technology is always changing.  In past iterations of antenna design I've always used EZNEC by W7EL.  It has always worked great, with theory and practice matching fairly closely, when all model elements are included (I've usually included my tower as an element in the model, as well as the near by roof rain gutter to get the most accurate results).

This time around I'll be using the program 4NEC2. A few test runs show me that it should work for me.  Notably missing are the antenna current plots which I always found useful to better see what portions of the system actually radiate, and what parts are eating the efficiency.

To get back into the process, I think I'll create a model of my current off center fed dipole, which I know already works, just to test the modeling software, and see if I can work with it, and include all the extra elements of near by metals.