Lifting the 10 Meter Yagis

Lifting the newly built 10 meter yagis onto the tower was done by tram line in a fashion no different than I've done before. However, I feel that it is worthwhile to review how it was done and to mention a few noteworthy points about the lift and antenna behaviour. A full assessment of their performance will have to wait until I gain more experience with them which, as you'll see, is not yet possible. 

Both of the 10 meter yagis were tuned using the same rope tram line used to lift the TH6 to its new rotatable side mount at around the 75' level of the 150' tower. The tram line and haul rope were then raised 40' and used to lift the lower yagi to its perch at 110' (on left). The side mounted lower yagi is fixed to Europe. 

The lift of the lower yagi was done without helpers. It was not difficult to achieve good balance and orientation for a small yagi and it is light enough to be raised by one fit individual. The lift was incident free so up I went and bolted it to the side mount bracket. That was the easy one of the pair.

To lower the antennas that were up top and to raise the upper yagi a steel tram line was anchored to a large and healthy tree in the bush at the opposite end of the hay field. I previously mentioned clearing a path to the chosen tree. Although not needed for raising this yagi, or for the preceding lowering of the TH7 and 40 meter dipole, using the tree was a trial run of the basic setup that I plan to use for raising the 3 element 40 meter yagi that is currently under construction. That's a big healthy tree, and a hefty chain to match.

As I briefly mentioned in a previous article, the TH7 and 40 meter dipole at the top of the tower were taken down earlier in October. Several friends came over to help on the ground and, as usual, I did the work on the tower. Only one friend (VE3KAE) was needed to raise the upper 10 meter yagi on the same tram line. For these higher jobs I prefer a helper even though in this case the upper 10 meter yagi is lighter than the lower yagi that I lifted on my own.

Notice the rope around the big tree? It is a safety line from the tree to the tram line cable termination. Winches are mechanical devices that can fail due to excess use and defects. Nothing is forever. When the tram line is at the desired tension, the rope is pulled tight and serves as a backup in case a problem arises. It does happen, as I can assure you from personal experience. No injury resulted in that incident (people or antennas) but it easily could have. Use a safety line.

Just because I like it, I included a shot of the upper yagi from the top of the 150' tower when it was less than 100' feet away (the tram line is 350' long, or 110 meters). Later I describe how I handled it when it arrived. The rigging for the tram ride is not always ideal for an easy connection to the mast.

The bracket for the lower yagi previously supported the TH6 that is now on a rotatable side mount further down the tower. I took the opportunity to improve the bracket and replace clamps that were showing their age. Although there are 5 elements squeezed onto a 24' boom, the wide director spacing of the optimized design allows the 10 meter yagi to comfortably fit on the bracket in any orientation without any element getting overly close to the tower.

There are nevertheless interactions, as I fully expected. For example, the SWR is not what it was when tuned. There are guys off the rear sides and one in front, towards Europe. Per my guy wire interaction model the interaction is likely to be primarily with the rear guys. I have not yet confirmed this in a model.

Although the guys are not terribly close (the picture is deceiving) and largely orthogonal to the antenna elements it takes little to disturb the pattern of a 10 meter antenna. The segments of the broken up guys are non-resonant on 10 meters but are large enough to couple regardless. I had a similar effect with the side mount 15 meter yagi but not the side mount 20 meter yagi. Size matters. I expect the antenna to perform well regardless since the impedance excursion is small and I know from other hams with similar installations and my own experience that gain remains very good.

I am unconcerned about a few minor lobes in the pattern since my interest is contests and a little radiation in various directions can pay dividends, and modest interactions don't reduce the forward gain by much. The minor lobes attract more callers without allowing too much QRM. Others with different operating interests might be more concerned. The only practical way to achieve a perfect pattern for side mounted 10 meter yagis (and for 6 meters and other VHF bands) is to use non-conductive guys.

Unlike the upper 10 meter yagi the SWR on the lower yagi is not what it was after the gamma match was adjusted at a lower height. I don't yet know how much of the change is due to tower and guy interactions and how much is due to me. The human body couples poorly but noticably on 10 meters. Antenna behaviour is affected by the proximity of my body (notice the reflection in the left panel).

The effect is reduced by standing vertically below the boom and by standing farther away. The good SWR of the upper yagi was not so good when I measured it the same way as I measured the lower yagi. The coax from the boom to the analyzer was only 2 meters long. The SWR on the right was measured when the antenna was at the top of the mast and I was at the bottom of the mast.

Now let's turn back to the raising of the upper yagi. Alan VE3KAE took a picture of me (on the left) as I took possession of the yagi at the top of the tram line. With the tram line slackened we lowered the antenna until the boom-to-mast clamp rested on the top plate of the tower. This was necessary so that I could move the chains and shackles for the tram pulley and haul rope onto the far side of the clamp plate.

The geometry of this rigging doesn't always make it easy to do the whole job with the same rigging. The large plate and integrated boom truss support made the transition mandatory. I was able to get one saddle clamp attached in this awkward orientation so there was no risk of an accident while I did the rigging. To save time I tossed no longer required chains and attachments to the ground. 

Always make sure to get your ground crew out of the way when you do this and only if you can comfortably send the material clear of guys and the antennas below. Stuff like this easily survives the 150' fall and it saves me the time and effort of carrying the rigging down with me. The steel strikes the ground fast enough that it is partially buried. On this climb I somehow knocked loose the little radio I used to talk to the ground crew and down it went. Unbelievably it survived the fall and still works!

With the antenna firmly clamped to the mast I rotated the boom so the elements were perfectly horizontal. I then adjusted the truss turnbuckles to level the boom. The turnbuckles are out of reach when the antenna is raised to the top of the mast. The next step was to remove the anchor plate (for the tram line and haul line pulley) from the mast, step the mast and hook a pulley to the top of the mast. The haul rope is threaded through this pulley down to the antenna.

It's a tedious process because I must then remove the steps to slide the antenna up the mast. Everything must be done with safety foremost, and that what takes the time. The procedure of the lift itself isn't difficult. I am deliberately avoiding details of mast stepping and mast climbing so that I don't give any ideas to overly enthusiastic readers. This is not a job for the tower novice.

With the rope pulled tight I loosen the mast clamps. While my friend pulls the rope I push the antenna upward. I again step the mast and follow it to the top. It's faster to remove the clamps and let the antenna climb freely, but it is not so easy to do the fine mechanical work of inserting the clamps (and not dropping hardware!) while perched at the top of the mast. So I do it the slower way.

To get the antenna to the very top requires rigging the haul rope to the bottom of the antenna. Otherwise you can't lift to the very top of the mast. Even so the rope jammed within inches of the top so we called it a day and I tightened the clamps, removed the rigging and climbed down.

I dress the cables accounting for the arbitrary direction the antenna ended up pointing. My home brew prop pitch motor controller allows infinite adjustment, and the direction pot on the tower has a 10:1 drive ratio, so that also allows essentially infinite adjustment. Calibration in the shack took 5 seconds.

The antenna works and it is ready for action. The lower side mount yagi will be without a coax connection until I build a 10 meter stack switch. It will make a triplet with the L-network 20 meter and 15 meter stack switches I built.

I'll close with a pretty picture. We are looking along the boom of the upper yagi towards Japan. The solar flux is high enough to work Japan on 15 meters and it won't be long before they are booming in on 10 meters. It is no accident that the 10 meter yagi project occurred this year: the solar cycle allowed me to delay until now, but no longer. 2022 is going to be a very good year for HF propagation.