Introduction
You've seen them for sale online, at some Hamfests, mentions of their for building antennas, I am talking about military tents poles repurposed and sold as military antenna masts.
They come in heavy duty fiberglass, smooth-walled and ribbed aluminum. Camouflage netting supports being repurposed and sold as insulator top pieces for a vertical or base. They end up being re-usable building blocks for antenna experimentation.
I started using the heavy duty fiberglass poles a decade ago as end supports for dipoles on top of the Hotel Pennsylvania for HOPE Conferences that would occur every two years there. We would build 12 feet of fiberglass mast for each end and strap the masts to whatever structure that was anchored to the building as possible.
Each conference they would be up there in the summer heat and winds for three days. The ends would be reinforced with duct tape. In eight years of use we hadn't had any structural failure with them but did started hearing some creaking in their last use.
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| Low Dipole atop Hotel Penn in NYC. Far mast just behind left corner of building |
12 feet strapped to the side of an existing structure might have been secure enough, but what about when it comes to how high can you stack military masts safely in open space using guy rings and ropes?
Use case
Is this a mast to serve as end point for a wire antenna, a mast for a beam or vertical, some combination? This adds up to how much load we are balancing at the top.
Will this installation be a semi-permanent setup at home or will this be part of a portable operation kit? For the latter weight, easy setup/teardown are considerations whether one or more people are involved.
Let's start with portable operations. and the most precarious setup.
Fiberglass Mast as Center Support for Wire Antennas (Dipole/V/OCF)
Base
Let start with ensuring you are setting up on level ground and what are you using for your base. The Paddle base is what is commonly used for flat surfaces as well as portable locations where you need to leave the least foot print on nature.
The mast kits used to include Paddle Bases but have since started to include the more expensive swivel stakes. These are good where ground is soft enough to pound them down into the earth.
When it comes to re-purposing or making your own portable base, I have used a plastic Christmas tree stand.
An item you could re-purpose for a base in a semi-permanent installation is a concrete block used for posts as sold by local home improvement stores.
They are too heavy for frequent portable operations but
a consideration for infrequent long operations setups like Field Day
at easily accessible locations.
Guy Ropes
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11.5 x 8 x 11.5 inch
Concrete Block |
For a total mast height of 24 feet, run guy ropes at 12 feet and then again at 20 feet for a mast that is 24 to 28 feet tall given a top load that will support the center of a wire antenna and 2/70cm mobile antenna.
While advise against going higher than 28 feet with fiberglass poles, for a similarly loaded mast that is 32 feet high, run guy ropes at 12 feet and then again at 24 feet.
To add some life to the fiberglass poles I've wrapped duct tape around the ends since when these poles fail it is often at those points.
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Tripod base using six
fiberglass poles |
If you want to run only one set of guy ropes for heights above 20 feet and have six extra fiberglass poles may you want to build a tripod base using a tripod adapter from companies like GoVerticalUSA or fabricating your own if you have the tools and materials. With a tripod added you can run your guy ropes at 24 feet for mast heights up to 32 feet.
Aluminum Pole Use
For this use since there is little weight difference between the fiberglass and aluminum poles, I use fiberglass poles for the legs of the tripod and all but the top two sections of the vertical mast.
With the top two sections fiberglass this reduces signal pattern impact to the wire antennas. while having a stronger support.
Aluminum Poles as a Portable Vertical
With tent poles being four feet in length, you and up lugging at least six poles for 24 feet to as much as eight for 32 feet. If you go with a tripod base you end up adding six poles to each configuration. Does not make for light carry for portable operation, just acceptable load for long operation setups.
So I got thinking about making an antenna out of the aluminum poles and cut a short section of fiberglass as a base.
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| Portable Vertical - Blue taps first aluminum pole, green is counterpoise laying on ground |
The diagram above is that idea as a 13 foot vertical. 'B" is a fiberglass section cut down to one and three aluminum poles stacked on top of it. A non-metallic guy ring with ropes is attached between sections '2' and '3' to keep the structure stable. A short wire is connected from the balun to bare aluminum using a metal hose clamp and a twenty foot wire is attached to the other end of the balun laid on the ground as a counterpoise.
While I have made a few FT8 contacts with it on 20 meters using a Yaesu FT-817 with a Z-11 tuner.
I need to do some more experimentation to see how far I can improve it to be a viable alternative to the performance of windsock verticals.
Will follow this article up at some point with results.
73,
- Joe, NE2Z
