22 February 2013

The ZS6TJS Mast. My learning experiences

This last weekend I took my new ZS6TJS mast to the field for the first time. OM Thomas Scott ZS6TJS had been extremely helpful in building me one of these masts before the ARRL Int. CW Contest. I picked up the mast from Thomas the day before. Thomas gave me a few tips on how to deploy the mast in the field. I was rearing to go.

ZS6TJS MAST in it's carrying case
 As you can see from the included pics, the mast is a
beautifully put together product. The kit consists of a very rugged carrying case, the aluminum mast sections (7*1 meter sections), two sets of guys, a hoist rope to allow hoisting of wire antennas, 3 tent pegs and an instruction sheet. The kit is professionally made. It is obvious that Thomas has access to the professional tools required to work in aluminium.

I had to get this mast in the air as soon as possible!

ZS6TJS MAST components

On Saturday I drove to the Krugersdorp game reserve picnic area. Here I found wide open spaces and a perfect area to set up the mast. See my previous blog for more details of this site. I first laid out the pieces on the ground, established where I wanted the mast to stand and measured out approximately 3 meters from the mast base to locate the first tent peg spot. I hammered the peg in very easily since the soil was quite soft. In fact I did wonder if the peg was going to hold. I then estimated an arc of 120 degrees from the base and hammered in the second peg, also 3 meters from the intended base. The same with the 3rd peg at an estimated angle of 270 degrees. I then slotted the first three mast sections together and inserted the first guy set onto the third section 'tongue'. Proceeding to slot the sections together, I then inserted the second guy set onto tongue number six before slotting the last and 7th section into place.

I then hooked two of the top guy ropes onto the appropriate pegs while leaving the third rope off it's peg. I simply left the lower set of guys off the pegs at this point.

Having done this I sat back for a few minutes and surveyed the scene, drank some water, took a deep breath, recalled what Thomas had instructed me and proceeded to 'push/lever' the mast into position by leveraging it upward in a line between the two pegged guys (easier done than said in this case). The mast went up without incident. Once in the vertical position, I then grabbed the third guy and walked it carefully out towards it's peg. Ha! The thing was in the air! I then walked around adjusting the guy ropes until all was square and the guys were reasonably taunt. I then hooked and adjusted the lower set of guys. I guess the whole job took me about 20 minutes.

I did notice that the guys were not quite evenly spaced at the requisite 120 degrees and that they also were not exactly an even 3 meters from the mast base.

Since I have a compass app on my blackberry, the thought occurred to me that I could orient one guy, let's call it the 'main guy' to face true north. I could then use the compass to more accurately locate the other two peg positions at 120 degrees and 270 degrees. Maybe I will cut a 3 meter piece of cord to ensure correct distance also. This is not so critical if the mast were to be used for simple wired antennas, however when using it for something heavier, such as a moxon, it is more important to set the guy locations correctly. Another lesson learnt. Ensure that all other humans, your radio gear and your car are out of range of a possible falling mast!

Next the fun started. Having erected the mast and now feeling full of confidence, I then assembled my ugly moxon. This is an ungainly antenna at the best of times. It is very easy to trip over wires and generally get things in a mess. Having done this, I then secured a piece of 1.5 meter doweling to the top of the mast using two hose clips. The moxon was then set atop the dowel and allowed to turn freely (hard to explain  but easy to do). The moxon at this point is resting on the extension piece which is designed to hold the feeder cable (I will get more pics on this). I then tried to hoist the mast up as before. However I found this extremely difficult. I would get the mast to a certain point but then the base of the mast would rise in the air and the assembly would fall to the ground in spite of me applying full muscle power. After expending much energy and now red in the face, I dug a small hole in which to set the base of the pole. Much the same as a pole vaulter would do. Now with the base somewhat secured in the hole I was able to apply force to the mast and walk it into the vertical position. This time the mast went up without incident. Once past the 45degree point it was very easy to push it to the vertical point. I noticed that there was certain bending in the mast as I was hoisting it through 45 degrees, however I did not feel that it was being over stressed. The lesson learnt by this exercise was that even a light weight structure such as my moxon was in fact very 'heavy' when attached to the end of a 7 meter pole. Physics lessons came back to mind. What was the formula? FORCE = MASS X MAST LENGTH.....hi hi.

Interestingly, at one point I was able to raise the mast quite easily using just 6 sections as opposed to the full 7 sections. I was amazed at the difference. But then of course I had to find a way to get the full height out of the system. I can say that once the system was QRV that all the effort is well worth it. What a great antenna!

When the time came to tear down I went through the same procedure in the reverse direction. Unfortunately at the point when the mast was at about 45degrees the base of the mast 'flicked' out of it's hole and the whole assemble came crashing to the ground. Luckily nothing was broken. In fact I realized that although the moxon looked ugly, it is quite robust. The 20mm pvc spreaders simply bending a bit when they hit the ground.

Another challenge I have found in the field is the rolling of ropes and wire in such a way that they do not end up in a tangle when the time comes to deploy. I like the velcro strips supplied with the mast, but they still don't quite solve the issue. I know all readers will identify with this problem. For another blog subject...

So what is the next step and what are the lesson's learnt? I will likely get a chance to try it all again this next weekend on Sunday afternoon.

  1. Use my blackberry compass and a piece of 3m cord to accurately locate the peg positions.
  2. Dig a mast base hole somewhat deeper. Say about 12cm deep. Keep the hole small in diameter (say about 4cms. Use my claw hammer and leatherman to dig the hole. If this procedure does not work then I will have to think about designing some kind of base plate. This I want to avoid if at all possible. My experience of field operations being to reduce the number of components required to an absolute minimum. Here the trade off is going to be between digging a small hole (manual labor) and installing a baseplate (manual labor plus another piece of hardware). Lets try the hole first.
  3. Take more pics of the proceeding. Maybe get the XYL, who is now back from europe, to take a video.

I will add to this report as I learn more.

Here below some pics taken so far.

Ugly experimental moxon on the end of a dowel. The dowel is fixed by hose clamps to the ZS6TJS mast

The mast is vertical, the pic is not! Note the cord  beam  rotator.
My operating position on Sunday. About 8 meters from the mast.

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