Portable antenna by SM0VPO

Hi Harry,
thank you for your fast answers. All seems to be clear  to me now. But when you have a bit of time, you might perhaps embed these answers directly into the article - for other potential makers.
I am surprised by your good experience with plywood as an insulator. I expected bad RF parameters of this material. Now I have to search a suitable box. Some plastic inserts in the holes may be added in case I find a box soaking more water. Plastic bottle caps may do. (I do not use a 3D printer yet. I was not caught by printing little Eiffel towers etc.)
If I am lucky, this antenna will work in my garden, too. As long as it is a temporary installation, my neighbour cannot object.

Thank you once more!
VBR from Ivan

Hi Ivan,
Lovely to get some feedback, so it does go to show that people do read more than 30% of the text n the web (published figure) 

Yes the 5.1m telescopic is very light so it sits in the box without any additional support. The box itself weighs about 6kg (at a guess), and it has never fallen over. I have never used it in gale-force winds, but I have been out in moderate winds where trees are swaying. I thought about that when I started using it, and my contingency play was to put a rock or a house brick in the box to stabilise it. I also thought about adding three bits of wood to the bottom that would fold out to give it extra support, but I have never had any problems whatsoever.

The box I normally keep indoors, so it is bone-dry. So I never use any form of insulation. If it were to get wet then I would use some form of plastic tube at the top and bottom, probably print something. But it has always worked for the last couple of years for me. I have never used it in torrential rain. I only use it on nice days when it is fun to be outside.

The connection between the loading coil and the bottom of the antenna is easy. I took apart a power block connector, you know the ones with a plastic terminal strip, used for joining wires, and each terminal has two screws. I used one of the brass inserts to make the connection between the aluminium wire and some braid from coaxial cable. The other end of the copper braid was clamped to the antenna with a "jubilee-clip", "hose clamp", " Stainless-Steel Clamp", "


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The box, by the way, is made of ordinary, un-treated, plywood, but when I got it I did spray it with that waterproofing spray for clothes and shoes. It is actually a packing box for some very heavy equipment, but they will not miss it from work :-)  I use the box to house my radio when I am taking it for a ride in the car. As you can see in the article pictures, there are frigolit / expanded polystyrene / cellplast sheets inside the box to protect my radio.


Have I answered all you questions? Do you want me to take some more detailed photographs? Perhaps, if you needed to ask the questions then I could have written it a little better, or added a more detailed picture.


Very best regards from Harry - SM0VPO

Hi Harry,
I have some questions about the portable antenna described in your new article. I bought a nice lightweight 5 m high aluminum pole (in several sections) from army surplus some time ago and this seems to be a project, which would put it in use.
1/ The antenna box stands freely on the ground? You say it needs no guy ropes. No ground anchor nor ballast inside the box is required as well? Does the antenna withstand moderate winds without accidents?
2/ Is there any insulation between the wooden box and the pole? Resp. are dielectric properties of wood so good that it can serve as a RF insulator?
3/ How the connection between the loading coil and the bottom of the mast is made?

VBR from Ivan