The purpose of this text is to document the installation of a two wire Beverage being installed at this station. In this document I discuss the problems encountered and the steps taken to help mitigate the problems. I have included drawings, schematics, charts etc where appropriate to aid in the understanding the text.
The desire to construct a Beverage came out of desperation. My transmitting antenna, an inverted L with a wire 70 ft vertical and 64 ft horizontal. It has four elevated radials and that are placed about 6 ft above the ground. This antenna is fed with RG-214 coaxial cable through a RADIOWORKS T5G UNUN. To keep ground losses to a minimum the antenna is not grounded at its base but at the POP, entrance to the house.
The problem with this antenna is that I hear broadband interference in the 160M band. I initially thought it was a common mode problem but have since found it to be effecting several square miles around my QTH. This presents an S6 signal in a 400hz bandwidth. If you listen in the AM mode with a 6kHz bandwidth you quickly discover there is a large AC component appearing on the receiver between about 1.7Mhz and 2.5Mhz rendering this antenna useless for signals at or near the noise floor. The farther you get from the 160M band the less of a problem it is and on 80M it can scarcely be heard in the AM mode. Strangely enough this problem abates when it rains indicating to me that it is a problem on the outside of a building. Go figure!
Figure 1: AC Line noise at WA3MEJ
Fall 2011 to Mid January 2012
The weekend before Thanksgiving 2011 I installed a 490 ft bi-directional Beverage using 450 window line which was supported with electric fence insulators nailed between trees and aimed at 35 and 215 degrees. The transformers were mounted in two gray PVC electrical type boxes that have rubber gaskets and the boxes suspended on the window line just inches above the ground rods. See below for the details
The Research Effort -
The first part of this effort was researching the Beverage antenna itself. I read everything I could find on the subject both on the internet and various texts that I have. This was a mixed blessing because although a lot of people have built and written extensively about this antenna, there is a lot of incorrect or half correct information out there making the mysteries that much deeper. Even ON4UN is not has not been immune from this problem. In addition much of the documentation is directed toward a single wire beverage and not the two wire variety.
During my wandering through these texts I found my share of formulae that were either incorrectly transcribed or specified for the wrong thing so I made sure that each formula I used could be verified by at least two sources. Admittedly some of the incorrect formulas caused only minor errors in the data but from the standpoint of technical excellence I just wanted to know exactly what was happening and why.
Once I had the formulas sorted out I decided to do my theoretical calculations using EXCEL This provides the opportunity to further the analysis by the use of graphs should the need arise. It was during this phase of the effort that I calculated the differential and common mode impedances of the antenna as well as several other parameters.
Beverage Construction -
After a lot of reading I decided it was time to start the installation process. I chose to use window line normally used for open wire feed line partly because I 490 feet on a roll from years past but also because keeping the spacing of the wires small with respect to height helped keep down selective fading of the signals. I also decided on a 7 foot installation height because it was the maximum height I could easily reach without the assistance of a ladder.
To install the antenna in approximately the correct direction (35-45 degrees) it was necessary for me to install it partially on wooded property owned by a neighbor. After receiving permission to install the antenna on his property I surveyed the location and selected trees for insulator installation. Co-incidentally this also compliment the 490 feet of window line I had pretty well. If I had another 100 feet I may have been able to squeeze it in but it would have been tough.
I purchased a bag of 25 insulators used by farmers for installing electric fence. These insulators were nailed to trees that appeared in as straight of a line as possible. To these insulators I attached two cable ties, one 3inch size went through the wire mounting hole on the insulator and a 6 inch cable tie went through the small cable tie in a wide broad loop. The 6 inch cable tie it was only tightened enough for it to catch. This allowed the window line to slip back and forth to even to the tension along its path. At both ends I attach a screw-in eye bolt to a tree. I fastened a piece of nylon rope to the window line at each end leaving only enough window line flapping in the breeze to reach the ground.
The basic layout for a two wire reversible Beverage is shown in Figure 2 and described in References 1 and 2 in only the most basic of terms. Still others have written of this antenna on their WEB pages 8 .
Figure2: This antenna requires 3 transformers, two hat match 450 Ω to the 50 Ω transmission line and a termination transformer.
Transformers - Figure 3: Gray PVC enclosure
The transformers were wound on FT80-75 because it is what I had on hand. These were housed in gray PVC boxes used for waterproof electrical outlets and shown in Figure 3. Notice the ladder line coming the top. The screw terminals was considered a very convenient way to attach the antenna. Also please notice the yellowish substance around the screw area, this is plain old Vaseline used to help slow down the oxidation. The ground is the blue wire that leaves the box from the bottom.
The boxes were mounted or rather suspended from the window line and the ground lead was used to keep the box from blowing around.
Real World Measurements -
During the installation process I broke out the analyzers. I have two an MFJ-269 and an AEA CIA-HF that I use somewhat interchangeably. Typically I use the MFJ for sweeping an antenna to get an idea what the SWR is doing because it does it so easily. I also use the CIA-HF for measuring impedance because it is a little more accurate and gives me both polar and rectangular coordinates and I don't have to do the conversions manually.
Figure 4: Screen capture of antenna before correct termination.
In Figure 4 we see a capture of the antenna before the termination transformer is installed. This was an attempt to get the correct impendence of the antenna. In this graph we see a maximum excursion of 38.2 and a minimum excursion of 22.5. Since this was measured through a 9:1 transformer this equates to antenna impendence of about
SQRT (38.2 x 9) x (22.5x9) =
SQRT (343.8) x (202.5) =
SQRT (69619.5) = 263.85 Ohms
Or about 264 ohms and if the impedance of the window line is supposed to be in the range of 400-500 ohms (nominally 450 ohms) then my measurements are either wrong or there is something else happening here. Since I performed this measurement in a rush because it was during a cold rain I cant help feel something is went wrong so I will be going out to do this measurement again before I rework the transformers with the correct ferrite cores. I just have to know what went wrong.
So eventually I gave up trying to figure out exactly what the impedance of the run was an made a transformer that approximated what I thought it should be. It seemed to work and like I said above the Beverage just seems to want to work and that's a fact. The problem with what I did is that I wound the transformers for 450 ohms and not the 263 ohms so I would imagine putting the correct transformers in the boxes will give me better performance this winter.
In Figure 5 shows a picture of the terrain and surroundings where the antenna is installed. As can be seen the brush is pretty dense but what is not easily seen is that fact that the soil is very moist and about 100 ft into the run is a spring and stream which makes navigating and installing the antenna run a problem. At one point I got stuck in the mud and could not reach the insulator because I had sunk about 6 inches.
Figure 5: Location of Beverage (click to enlarge)
UPDATE - 08 November 2012: Evidently the this antenna has been laying on the ground since the storm that hit this area on June 1 of this year. It was at that time we had a tornado hit the back of the property and lay several trees down on the roof of my garage. Evidently it ended at my property.. but boy it did take a lot of trees down in its path. During this time my inverted L antenna also came down. Unfortunately I did not see the Beverage on the ground until now.
In the next several days I will be putting it back up in the air, this won't be hard but will take a little time because there are some nice size limbs laying on it. Interestingly enough this antenna still works great on the ground.
1: "The Beverage Antenna
Handbook", Victor Misek (W1WCR), 1987
2: "Antennas and Techniques for Low-Band DXing", John Devoldere (ON4UN), ARRL, 1994.
3: “Two Wire Beverage”, Jeff Parker (KA1GJ)
4: “The Wave Antenna for 200-Meter Reception”, H.H. Beverage
5: “A $50 Beverage”, Randall Thompson, (K5ZD)
6: “Beverage Antennas for HF Communications, Direction Finding and Over-The-Horizon Radars”, Litva and Rook
7: “Beverage Antenna for Amateur Communications”, Belrose (VE3CV), Litva, Moss, Stevens (VE3CYO)
8: “A Reversible Beverage at ZL3IX”, WEB page of Greq Smith ZL3IX
490 ft Beverage Aimed at 35 & 215 deg
Copyright (c) 2012
Jim Sears WA3MEJ
Added 17 August 2012
Updated 08 November 2012