Beverage Site and Construction Plan

I am on course to install more Beverages and a switching system as my preferred low band receive antennas. As I mentioned in my yearly plan I was wavering on whether to use Beverages or vertical arrays. I have the room to do either, which is not something many hams can claim. But having the option requires that I make a choice.

Spring is not my preferred time of year to work on receive antenna. There are tower jobs waiting and I don't need low band antennas during the warm months when activity is elsewhere. The global pandemic lock down keeps friends away and I need helpers for most tower work. Therefore I am using the time to work on projects on the ground. Beverages are ideal.

In a coming article I will describe my next Beverage antenna, which is reversible north-south. Here I will revisit my site plan with respect to receive antennas and how I am proceeding.

Choosing Beverages

Beverages have the advantage of economy and simplicity. The construction of switching systems is not complicated so this work does not greatly effect other antenna projects. Since I enjoy designing and building antennas the choice of Beverages is a good one.

Beverages can be bi-directional, uni-directional or uni-directional and reversible. Reversible cuts down on cost and physical complexity at the price of electronics for switching and tuning. I chose reversible coaxial Beverage antennas as my path forward. That may change later if performance does not meet my objectives.

There are commercial products available for Beverages and vertical arrays. Beverage electronics are fairly simple and can be tackled by any ham. Vertical arrays are more complex. Commercial products take on the burden of vertical element phasing, combining and switching. None are inexpensive but are necessary for most. Many hams I know use them, or two for simultaneous independent use on two bands. These include receive triangles, 4-squares, 8-circles and BSEF arrays.

The improved directionality and therefore RDF (receiving directivity factor) of vertical arrays is good for DXing. All of the best vertical array have better RDF than single Beverages. For contesting a little "leakage" in other directions helps avoid missing many weak callers. That is, higher RDF can be detrimental in contests. So Beverages it is even though I have ample room for either.

Phased Beverages can equal the performance of many vertical arrays. In future I may experiment with these, in particular doubling the northeast Beverage to make an end fire array to Europe. 

Site plan

Refer to my original site plan for this QTH and you'll see the large area of bush that I am using for receive antennas. Although working there is difficult for much of the year it has the advantages of being out of the way of farm equipment, suitably separated from other antennas and far from RFI sources.

I am making use of trees for many of the supports. Periodic brush clearing and the risk of damage by falling trees and branches is balanced by their convenience and almost zero cost. I must also site antennas to minimize damage from wildlife and occasional use of machinery in the area.

Satellite image from Google Maps

The northeast 170 meter long Beverage was installed a few years ago. It is unidirectional. My intention is to make it bidirectional, but not immediately. The antenna I am currently building is the north-south reversible Beverage running through the tree line between fields. Next will be the east-west reversible Beverage, possibly this spring or more likely in the fall.

The prospective northwest-southeast Beverage is lowest priority. Northwest is of limited use compared to the north Beverage. Southeast is far more important since it covers Africa and occasional skew path to Europe and other points. Similarly southwest is important for south-central US and the south Pacific. Unlike the higher bands I need good coverage of the US since the high noise level on 160 and 80 meters covers up many smaller stations I want to work in contests.

The switching system will be located near the west termination of the east-west Beverage. I have all the parts in hand to build it. Routing of the control cable will either parallel the transmission line or buried in a trench to the 150' tower where I have buried cable to the shack ready for use.

The transmission line follows the tree line west and then south to the Trylon tower adjacent to the house. This route minimizes coupling to the transmission lines of other antennas. It takes very little RF incursion to compromise RDF. For most hams this is not a problem since transmission and reception is rarely concurrent.

The bidirectional Beverages are 150 meters long. The RDF is almost as good as 175 meters and can be made from a 500' (152 meter) reel of inexpensive RG6. I don't want the main lobe to be too narrow since this can be problematic for contesting use. The antennas can be extended by simply adding more RG6 and moving the ground rods. Non-resonant antennas are nice that way.

Notes on Beverage siting

The placement of my Beverages is inspired by the experts. One is ON4UN and his indispensable book Low-Band DXing. If you care about the low bands you must have this book. You will learn not only the how but also the why.

The other is W8JI. His web site has a lot to say about Beverages and other receive antenna topics. ON4UN quotes from him extensively. While there are other reliable resources you won't go wrong with must these two.

Overlap: Beverage antenna can run right over each other without pattern distortion, provided the conductors don't touch. However the terminations should be at least 5 meters apart and 10 meters is preferable. Otherwise the impedance between their ground rods and radials may be low enough to allow signal incursion and therefore reduced RDF.

Height: Beverage gain increases with height although the maximum frequency at which they are useful decreases. My Beverages heights of 2 to 2.5 meters are a compromise between gain and good performance on 40 meters.The height allows for easy maintenance and reduced risk to and from deer, machinery and people.

Common mode: Grounds and chokes at critical points are required to eliminate common mode signals that can ruin RDF. Those points are the terminations, switching units and at intervals along transmission lines. This is especially important when a transmission line parallels a Beverage for more than a short distance. The easiest and cheapest choke that I like is a 1:1 balun on a ferrite core. If you require continuity for DC switching current on the transmission line an alternative is to wind the coax on a suitable ferrite toroid.

Length: RDF increases slowly with length (relative to wavelength). Although there are no magic lengths the minor lobes rise and fall as the length changes and can be chosen to maximize F/B or place pattern nulls towards a noise source. My Beverage lengths of 150 to 175 meters have a good RDF on 160 meters while not having too narrow a main lobe on 40 meters.

Proximity: The farther a receive antenna is from noise sources and transmit antennas the better. The area I've chosen for the Beverages is far from my house and very far from neighbours. The only potential problem area is the distance from the east-west Beverage and the 80 meter array radials. No degradation was noticed with a temporary 90 meter long Beverage so I probably won't have a problem the 150 meter long east-west Beverage.

Sharing: Should I ever choose to experiment with high RDF vertical arrays they can share the same field. Interaction issues are similar to overlapping Beverages. A good illustration of this is the receive antenna setup at W5ZN. The reason why receive antennas can coexist is their very low efficiency. The loss resistance (small size, ground loss, etc.) greatly reduces mutual impedance.

Next steps

The north-south Beverage antenna has been installed and it is working well. Testing will continue to determine how well. In the absence of a switching system the coax to the northeast Beverage was temporarily moved to the new antenna for testing. DC is injected into the coax to switch directions. Expect an article on this antenna soon.

If the pandemic situation continues and help for the big jobs is unavailable I will work on the switching system and shack controller. With more delay I might also install the east-west Beverage. All of this work must cease by May to avoid the start of tick season in the dense bush. I really don't enjoy that.

Within a month I may have a 5-direction highly effective receive antenna system. Summer is not when it's most useful but during the current crisis you do what you can.