HOME Ham Projects Outward Links Links to this site
I have seen various designs for a simple mast base held in place by rolling the tire of a vehicle or trailer on it. I have no real access to metal working equipment, so I have been thinking of a simple alternative that didn't require any special tools, welding, or actual skills to speak of.
I have a segmented flag pole to use as a mast, so it requires very little support and already has a pulley and lanyard installed to use in hoisting an antenna after the mast is in place. This means that only the flag pole has to be man-handled in place, and the mass of the antenna added when it is safely up and self-supporting. I did decide to use some praces about eight feet up the mast to keep it from swaying, although in light winds with a reasonably sized antenna they are probably not needed.
For my prototype I scrounged up a piece of 2X6 and a piece of 2X4 used lumber, each about thirty inches long. I started by using two 1/4 inch diameter lag bolts, four inches long, to secure the upright 2 by 4 to the horizontal 2 by 6. I pre-drilled to allow the lag bolts to go in without too much force and almost no chance of splitting the wood. I put a bit of white glue in each hole to both lubricate the lag bolts on the way in and help them hold solidly once in place. I like to use fender washers to distribute the force from the lag bolts over a larger area.
Given the amount of leverage the flag pole would put on the junction of the two pieces of wood, I decided to reinforce it with a substantial corner brace, held in place with 3/4 inch long lagbolts, which I also pre-drilled and coated with white glue. The resulting base was very strong and shows no signs of movement in use.
I used two conduit clamps with 1/4-20 bolts to hold the flag pole to the base, and tested it with the rear wheel of my pick-up holdiong it down. with the bottom 5-foot segment of the flage pole in place it was very solid when shaken and pushed around. When the remaining segments were installed, making the flage pole 25 feet tall, it was still very steady.
Not having a philosophical problem with over-building, I also fashioned a couple of very simples sway braces. I used two inexpensive 1X2s, each 8 feet long. I put small hinges on one end and drilled two holes near the other end. I use a hose clamp to attach the braces to the mast, and use heavy-duty wire ties to secure the other ends to the cargo tie-downs on the truck.
During Field Day, 2012, I attached the balun of a parallel dipole to the lanyard and ran it up to the pulley. With the ends run to nearby trees this antenna and mast was used for our GOTA station, making dozens of contacts across the US. It will be a simple matter to adapt other antennas to be hoisted in the same way.
A 25 foot mast is tall enough to work fairly well on the upper HF bands, and do a fine job on VHF and UHF. For a portable mast, this flag pole and base is very robust and easy to assemble by one person. The only remaining step is a simple paint job to weather-proof the base and make it look a bit more finished.