Field Day 2022 Prep: Practicing With The VHF Mast
Field 2022 is upon us! And I am a freelancer this year, in contrast to the preceding three years as a Field Day coordinator. In my mind, this meant I would tour around and insert myself as a guest in various other club events. That said, I have been really enjoying the direction that one of my local clubs has been going. The fact that it is my home city club, that I can reach its repeater easily from my qth, and that I have attended almost every Monday night club repeater ragchew nets over the past year or two, has propelled me to inch a bit closer to them. It helps too that their president is a skater!
So, with the COVID quarantines now in our past, and clubs reemerging for group events, this year I will be spending a bulk of my time with the home city group in their new FD locale. And AA1F will be with me for his first Field Day too! Our assignment is to supply and set up the VHF station, complete with a Diamond X30A 2M/70cm vertical, an Arrow 146-4S 2M 4-element beam, and an Arrow 52-4S 6M 4-element beam. We will be mounting it all on a Go Vertical Portable Tower Mast Kit.
If you visit the Go Vertical USA website, the first thing you notice is that these kits are sold out. They are also $300 dollars more than what I paid for mine two years ago. I am tempted to reach out to the owner, a seemingly very responsive individual, and ask him what is going on.
The kit is composed of 6 aluminum mast legs that form the tripod and 8 aluminum center sections that form the mast. And a pyramidal device that holds the tripod legs in place and has a hollow central channel through which the mast slides. The graphic below uses images I lifted from the Go Vertical USA website. You can see the center tripod piece, the plug end of each mast piece, and the cuffed socket ends that form the tripod legs, and the smooth socket ends that have no cuff that form the mast. The important distinction between the socket ends is that the cuffed pieces cannot slide through the tripod centerpiece, and therefore there is no easy way to push up the mast from underneath. If you acquire one of these kits, make sure to sort out these pieces first before putting it up!
The 2M beam and vertical antennas are shown below.
Nellie of course has to be in the middle of the action. In fact, she stayed pretty oddly close to the set-up of this antenna system. All we can think is that in her mind we were setting up a tent, and she tends to like to be the first in one when we camp. In the foreground, you can make out the reflector and driven element of the 6M beam.
If you take a careful look at the picture below, you can see that the mast that the antennas are attached to is gray, as opposed to the green of the military mast. These are two sections toward the top of the Max Gain Systems push-up fiberglass mast. You can read more about my use of the mast here and here. One of the 4′ sections of the telescopic MGS mast fits perfectly inside the military mast tubing. And due to the fact that the plug end of the mast section is of smaller diameter than the rest of the tube, the MGS mast piece will not slide through. This allows for easy rotation of the antenna stack as it spins around within the military mast tubing. We tied long strings to the front and back ends of the 6M boom in order to be able to swing it into position and then tie it down to keep it in place.
It also turns out that putting the antennas on like this also makes it easy to work on them. Note that the tripod legs each only have one section in the above picture, making everything fairly low to the ground. In the final configuration, as seen below, each tripod leg has 2 sections. In order to successfully feed the mast sections up through the center of the tripod pyramidal center piece, both sections of each leg of the tripod have to be on. If not the center piece of the mast is not up high enough to be able to push additional mast pieces through it.
Once all of that was established, we started lifting the mast up and adding pieces underneath it. It is imperative to hold down on the tripod pyramidal centerpiece to avoid the tripod leg sections from coming apart and causing the whole contraption to collapse.
The other thing to notice is that the plug end of the mast sections is on the ground with the non-cusped socket end facing upward. This orientation is necessary in order to be able to slip the MGS fiberglass mast sections into the military mast section.
If you look really carefully at the image below, you can see guy lines that meet up with the center of the mast. At this point, the slight bulge in the mast is a ring shaped piece of metal with perforations in it that slips between two pieces of mast sections. Now that you know what to look for, look at the picture above and you can see it better.
The problem with these guy rings is that you cannot slip them up through the mast in order to install them. We solved this problem by removing one section from each of the tripod legs to lower it. This would mean that the lowest section of the mast would be taller than the tripod pyramidal centerpiece. Then we lifted the entire mast up and off of the lowest section of mast, holding it freely up in the air. We quickly positioned a ring in place, and then slipped the mast back on to the lowest section. An improvement would be if they clasped into place rather than had to be slipped on.
Here is a view of the mast from the top of the cargo trailer. You will see there are two extra sections of aluminum mast we did not use. Technically, this mast could go nearly 8 feet higher. The wind was extremely strong though so we thought we best stop at 6 sections.
You can also see that we have two cinderblocks at each of the 3 guy lines we used. On actual FD, we will use two guy rings instead of one, and have an additional 3 ropes attached to 2 more cinderblocks each, for about 450 pounds of weight holding the system down.
I tested the SWR of each antenna, which in some ways looked a bit wonky and was bouncing around as the antennas moved with the wind. I am blaming the RG8X coax, but hopefully everything looks good on FD where we will be using a more suitable cable for VHF. Regardless, the SWR was under 2 for both 2M and the 6M beam across their respective bands. We were able to hit local 2M repeaters, including the one in Lake George NY, 52 miles away as the crow flies. We did not make any simplex contacts, including on 6M.
So with antenna testing a success and still 2 hours of daylight left, AA1F decided to cap off the day with a sunset drive up Mt. Utsayantha for a quick Summits-On-The-Air activation.
I would say it was worth the trip. (Happy Birthday and Father’s Day Mike).
KM1NDY