Tip #2 - HF Antenna - NVIS type - 2006 Design
As shown in the picture to the left, I made a few minor changes to the original design of this NVIS antenna kit. I replaced the hammer-in support rope stakes with a screw-in variety. At first I thought that they wouldn't be able to withstand the torque or pullout stress. A few tests showed me I was wrong. They are easy to use and easier to remove from either soft or hard soil while still supplying enough strength so that they won't pull out like a conventional stake might.
The picture also shows the kit without the coax cable and ground reflector system that were a part of my other pictures. I did this to give you a better view of the antenna, itself. The ground reflector system is very important in creating the RF waveform needed for NVIS signals and I have designed a reflector system which is easy to deploy yet suits the ground conductivity of our area. It took many field strength experiments to come up with the ideal reflector design.
There are three antenna supports, all of which are 5 feet tall when assembled. This height, after field testing, I feel is not only RF adequate to create the "half grapefruit" lobe needed for communications within a 400 mile circular range but it also makes the antenna easier to handle and construct. With this height above ground, it also means that it lessens the reception of both static crashes AND European broadcasters on 40 meters making it very valuable during emergency communications in south Texas. If every emergency communications operation in south Texas, that used HF, were wise enough to also use the same type of antenna system it would make a very reliable communications web between all counties. I have also designed a NVIS antenna system which will create the same radiation pattern when it is installed on the roof of a building, such as at an emergency operations center. The reflector system is completely different to compensate for "pooling" and nearby metal structures.
Visit http://hometown.aol.com/alonestaryank/NVISKIT.html for more details, construction instructions and full parts list for building your own portable Texas NVIS Antenna. 73 de Bob W2IK