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From a reply to a previous post I've been told that a horizontal tube half a wavelength long mounted right at the junction between the boom on a vertically mounted yagi and a vertical metal pole will present a high impedance on the mast and allow the Yagi to work properly despite the presence of the metal mast, can anyone shed any more light on this idea ?

Mounting a 10 m vertical Yagi on a non-metallic pole is not a good solution in my opinion and the only other way to do it is mount from the back (not easy if you have a rotator) or phase two yagis together just so they can be mounted on a horizontal connecting boom which balances out the weight,

Or worst case I can make a combination horizontal / vertical Yagi with the vertical elements in front of the metal mast and the horizontal elements sprinkled behind and among those so it's balanced, but then the antenna will start to become pretty long and unwieldy.

Mike Waters
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Andrew
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3 Answers3

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A very common approach that is used for satellite antennas is a solid, fiberglass mast. These are readily available from amateur radio distributors.

The fiberglass mast has sufficient rigidity that I have used it in a horizontal boom configuration with large, crossed polarized yagi antennas with preamps on each side and there was no noticable sag. You can certainly use it as a vertical mast so as to avoid any gain or impedance degradation of your vertical yagi.

You may even find a hollow fiberglass mast would prove sufficiently stiff for the job although you may need a reinforcing material inside the tube at the clamp points to prevent crushing it.

You could also fashion a hybrid metal / fiberglass mast using short fiberglass sections inserted into the metal mast to join the mast pieces so as to break up the electrical length of the mast to make it more nearly transparent on 10 meters.

Glenn W9IQ
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You mentioned to "mount from the back", which is not easy, but you can add an extension of the boom backward to act as a counter weight for the antenna. (Usually vertical polarization is for working a repeater! Is that what you will be using the antenna for?)

quintablet
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  • If mounting from the back, a better way would be to run a diagonal support rope from the top of the mast to the front of the antenna. However, as Glenn suggested a fiberglass mast fastened near the center of the boom is even better. – Mike Waters Mar 04 '19 at 13:35
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Mount the antenna at a non resonate point so it has the least amount of play in the scheme of things. It is simple look at your YAGI design just put the pole (mast) in between two of the elements that way it is in a null as far as the antenna is concerned. Laurin WB4IVG

Laurin Cavender
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