Beverage Repair and Maintenance (again)

Beverages are fantastic low band receive antennas. They're simple and inexpensive, yet they perform exceptionally well. With a little bit of simple electronics and winding small transformers they can be made reversible, giving you two directions. My first unidirectional Beverage toward Europe was installed soon after I moved to this QTH. Along with my first ever full size 160 meter antenna I had a wonderful time on top band.

The one thing Beverage antennas need that most hams don't have is lots of space. A Beverage for top band is typically from 100 to 200 meters long. I am fortunate to have the space. They are located in an area of derelict bush that hasn't been farmed for decades. The 3 reversible Beverages cover the 6 most useful compass directions. There are plans for a fourth, but the need isn't urgent so I have deferred the work in favour of other projects.

Beverages have their negative points:

• They are typically no higher than 3 meters. They are susceptible to damage from people, animals and vegetation. Search the blog and you'll find several articles about the construction and maintenance challenges I've dealt with since putting up my first unidirectional Beverage in early 2017. Maintenance and repair twice a year has become routine.
• Despite being so low, Beverages are highly susceptible to lightning. Their length easily induces high voltage currents from nearby strikes, and they provide a conveniently large number of junction points for strikes to reach charge reservoirs in the ground. Many hams disconnect their Beverages during the summer when lightning is common and activity on the low bands declines due to the high atmospheric noise.

It was September before I could access most of the Beverage system. The hay, insects and summer growth strongly discourage anyone venturing into the fields and bush from late spring to late summer. Over the past few weeks I've discovered that the lightning strike earlier this year did more damage than I realized. It will be some time yet before the system is back in full service.

The first job was to retrieve and repair the Beverage remote switch. It was easy to reach once the hay has been mowed. All the relays had to be replaced, and for the same reason as the previous time lightning struck. All I had in my stock was SPDT reed relays so I used those. Since I only had 3 and there are at present only 3 Beverages, I left the fourth port disconnected. An important advantage of SPDT relays is that I can ground the feed line to the Beverages when they're not in use. That provides limited protection against lightning. I'll take it.

Unlike the SPST reed relays these replaced there are no internal flyback diodes. To make the job easier I didn't put any in the switch. I will add them to the switching system in the shack. Their location is not critical, so putting them close to the electronics they are meant to protect is perfectly acceptable.

Lightning was not content to only wreck the relays this time. The pair of 0.1 μF coupling capacitors were blasted by the surge. These capacitors are only rated for 50 volts. Had they been rated for a kilovolt they still might not have survived. I'll order more robust capacitors for future repairs.

With the remote switch tested and reinstalled I proceeded to test the rest of the system. The east-west Beverage was completely dead and the northeast-southwest Beverage was bidirectional and unresponsive to reversing current. The north-south Beverage was unaffected because the electronics were taken indoors before the strike due to a switching problem. However I have yet to fix it, with the result that none of the Beverages were in service.

I brought the head ends indoors for examination. I also performed simple tests of the Beverage wires and reflection transformers and all passed. That was the only good news. I waded through the bush and confirmed there was no physical lightning damage, but there were other problems which I'll come to shortly.

Above is the head end of the east-west Beverage. The blocking capacitors and the RF choke of the bias-T for the reversing current were blasted apart. At least one transformer winding arced and melted through. Scorch marks on the plastic enclosure from arcing are obvious. Several copper traces on the underside of the PCB vanished.

Despite having done no further component tests I think it is fair to say that the head end may be a total loss. It will have to be rebuilt from scratch. The northeast-southwest head end has less damage and may be salvagable by replacing a few of the parts. I plan to order new relays and rewind the transformers for both head ends. One of the transformers of the north-south Beverages will probably also need to be replaced.

I reconfigured my Beverage test fixture as a differential mode head end and installed it on the east-west Beverage. There is a 5:2 transformer inside and a pair of 0.1 μF coupling capacitors. The impedance match is not exact but good enough. The capacitors prevent a short if reversing current is accidentally applied by the operator (me!). West is a useful direction for the Pacific opening this time of year. It's a temporary measure.

Parts need to be ordered and the head ends rebuilt. I'll do that in the coming weeks. In the meantime there was routine physical maintenance to be done to repair and prevent animal and vegetation damage. The only animal damage this year was to the northeast termination of the northeast-southwest Beverage. It was most likely caused by a deer walking into the wire running between the reflection transformer and ground rod. 

The wire was torn off the ground rod clamp and the transformer enclosure pulled off its mounting. The damage was easy to repair. To prevent a repetition, I stacked a pile of stones under the wire. There was an ample supply within a few meters since, as was typical when the land was originally broken for farming, the stones that litter the soil in this area were rolled over to the fence lines. 

What I should do is lengthen the ground wire so that it can lie on the ground out of the way of trespassing wildlife. The extra length of wire will have a negligible impact on antenna performance. Perhaps I'll do that once I have other jobs out of the way. The stones can remain to protect the ground rod.

The rest of the maintenance involved trimming vegetation. It is often quite a surprise to see how much the trees and bushes grow over the summer. Branches that were previously trimmed have grown back and in many cases tangled in the Beverage wires. New bushes sprout up where there was none before. If left uncut they will threaten the Beverages next year. It's unpleasant and tedious work, but it has to be done.

Especially problematic bushes and trees are cut down rather than just trimmed. For example, the thorny bush above was chopped down on this outing. In some respects it's a shame to have to do it, but this is wild secondary growth on an abandoned farm field that has no particular value. I am tempted to bring in a large tractor and flatten the vegetation.

Last year I had a problem with the wires of the northeast-southwest Beverage. They would oscillate in the breeze and eventually spin and short together. When I installed the original single wire Beverage I used every available tree and bush along the route as support. There were no artificial supports. 

This haphazard approach simplified construction but created a problem when I twinned the wire to make the Beverage reversible. The Beverage is not quite straight. It wanders a little one way then the other to utilize the available supports. Beverage performance isn't affected by minor deviations.

As vegetation grows the deflection and spinning tend to increase. In two instances I had to decouple the wires from the supports without installing a pole to replace them.

My interim solution was string attached to the Beverage at those two points and tying them to small bushes. It didn't work as well as I'd  hoped. During this maintenance outing we installed a PVC pipe at the most problematic location. Spinning is far less likely since both wires are firmly attached to the pipe. Over time I will have to do more of this and perhaps abandon all of the natural supports.

To ease the job this fall, I was assisted by my friend and favourite ground crew member, Alan VE3KAE, along with his trusty axe. Why suffer alone when you can share the misery.

The vegetation growth was serious enough that it took us longer than expected. There was no time afterwards to work on other projects. I have yet to lay out the radials for my big 160 meter vertical. We got a good workout and had enjoyable conversations as we inched along through the bush. I can unroll the radials on my own another day.

In light of all this complaining and frustration there is the inevitable question: are the Beverages worth all the work? It is a question worth contemplating since there are alternative low band receiving antennas.

Beverage are simple and effective but vulnerable to nature. I may no longer be able to keep them connected during summer. That hasn't been a major problem because I have to disable my big vertical during the summer. That may change in the future. 

It has always been my intent to have a second low noise receive antenna system for multi-op contesting. That would be a short vertical array. They are reasonably compact, less susceptible to nature's assaults and in most cases have superior performance (RDF) in comparison to Beverages. I have enough room for Beverages and a vertical array.

Since these systems are very finicky to design, build and adjust most hams use commercial products. They can be quite expensive. Further, the amplifiers they require must be sufficiently robust to withstand a simultaneously transmitting kilowatt during contests; at other times it is not an issue. I know hams that have had to deal with pre-amp overload when using their vertical receive arrays during contests.

Another alternative is to go back to unidirectional Beverages and simply put up more of them. They're simpler and the vulnerable reversing electronics are absent. They're easier to build and repair. But do I want double the number of Beverages to maintain out in the bush? Or perhaps have several that are installed in the open fields during the fall and removed in the spring? A lot of coax must also be deployed since it is not convenient to have the feed points close together given the constraints of my property.

By laying out the pros and cons you can perhaps better appreciate the alternatives. Every low band operator must choose. It comes down to trade offs of money, ability, performance, land use and effort. Two hams can come to opposite decisions and both be right. 

I am not yet near a decision and I won't make one this winter. There's a lot to mull over.