Topband: Beverage Antenna

[Walter Schulz]

Hi,
I thought to jump in here with my two cents worth of nonsense, you see I live in the woods, and don't see to many people these days.....thank God...so here goes it!!!

The single wire Beverage works on the theory of wave front tilt, consulting the books of 1915 to 1917 by Prof. Zenneck you might of heard of something called the Zenneck Wave.
On ELF, VLF, and LF, that's all the frequencies or wavelengths below 500 Kcs or the medium wave broadcast band the wave front travels outward from the antenna transducer (vertical monopole) along the earth's surface and the bottom side of the ionosphere. There is no skywave that is received. The earth is a dissipative medium, which means that its something like a resistance when compared to the air, therefore the wavefront as it travels forward and outward starts to tilt forward. Depending on the soil it will tilt forward to approximately 1 to 10 degrees, over salt water and salt water marsh it remains perpenicular to the earth's surface. What does this mean? As the wavefront leans or tilts forward it cuts across the Beverage antenna inducing a voltage in the wire. This voltage builds in amplitude as it travels to down the wire to the receiver. Signals coming from the opposite directions do the same, build in amplitude with one big difference. Upon reaching the terminating resistance the voltage is dissipated across the resistance. No standing wave reflected back to the receiver, if the terminating resistance matchs the surge impedance of the Beverage single wire. Here is where it gets interesting. The resistance is grounded and the return path goes thru the earth back to the receiver side ground to complete the path. Therefore, if we treat the Beverage as a single wire transmission line we find the actual surge impedance impedance of the antenna as approximately 470 ohms. But we must also include the dissipative resistance throught the ground. Tom, W8JI, as a pretty good handle on explaining it to you. Tom is right about the wire under the Beverage is wrong, not necessary, a no-no, Mr. Misek as it wrong.........

Here's the catch 300 Kcs to 3 Mcs is where transitional propagation takes place. Waveguide mode theory is no longer valid as we apply in ELF, VLF, and LF. At 160 meters the ground wave from the transmitter only travels approximately 100 miles from the monopole, and then vanishes from the surface of the earth thru absorption. We depend on skywave, chordal ducting, ionosphere tilting, and ducting South to North. You are receiving the sky wave which is a tumbling wave front arrivaling at the antenna and traveling the antenna axis. You are no longer receiving just a ground wave or E Field, but an ellitpical wavefront. You do not need another wire under a single wire Beverage, it does absolutely nothing for the antenna system.

There is another way to overcome dissipative ground loss in Beverage antennas, however, its a little to complicated for me to explain to you presently.

Why multiple wire Beverages antennas, we can add another two wires to a single wire Beverage, what this does is decrease the velocity of propagation on the antenna. It also smooths out the impedance bumps in the antenna. Namely it makes the antenna appear electrically longer than it really is, but at a cost, the cost is less gain.

Do not confuse the multiple wire Beverage with the 2 wire beverage bi directional antenna system. It works on a different principle than what I have described. It is not to well known. You will do fine with a single wire in multiples of halfwave 3/2 will work just fine. Approximately 800 feet on 160 meters. I would go by W8JI webpage it describes much of the basics and you won't go wrong.

I use 3 Bi directional Beverages here, NE-SW, SE-NW, N-S, I used RG59 to feed them. Reflection transformers and on each end 7 ground rods, 8 ft long in HEX Configuration tied together with no. 8 AWG copper wire.

Good Luck,
Walter 
K3OQF/T5 //VQ9TD
Master Radio Electronics Officer
U.S.M.M.,Retired